RESOURCE USE AND CONSERVATION AND ENVIRONMENTAL IMPACTS IN THE TRANSITION FROM CONFINEMENT TO PASTURE-BASED DAIRIES By M. Melissa Rojas-Downing A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Biosystems and Agricultural Engineering - Master of Science 2013 ABSTRACT RESOURCE USE AND CONSERVATION AND ENVIRONMENTAL IMPACTS IN THE TRANSITION FROM CONFINEMENT TO PASTURE-BASED DAIRIES By M. Melissa Rojas-Downing In recent years, many farms have transitioned from total confinement housing to a pasture-based system in an effort to reduce labor and production costs and improve profitability. There is a growing interest in biogas recovery among livestock producers to reduce energy costs and manure odors but the economic benefits of anaerobic digestion (AD) on small farms is not well known. A comprehensive analysis was conducted using the Integrated Farm System Model, to describe, evaluate and compare the economics, farm performance and environmental impacts of representative dairy farms in Michigan transitioning from conventional confinement to a seasonal- and pasture-based systems, and evaluate the potential for integration of an AD in the confinement and seasonal pasture systems. In the economic analysis the annual pasture-based system had the greatest net return to management and unpaid factors followed by the seasonal pasture and confinement systems. The addition of an AD on a 100-cow, total confinement dairy decreased the net return to management and unpaid factors by 15%. Cycling manure nutrients led to an annual depletion of soil P and K on the confinement dairy and a build-up of P and K on the seasonal- and pasture-based dairies. There was little change in N, P and K or carbon loss to the environment due to AD. In the seasonal and annual pasture-based systems, ammonia emissions increased by more than 100%. The water and reactive nitrogen footprint increased and energy footprint decreased compared to the confinement dairy. My dedication is to my husband who with all his love, support, sacrifice, encouragement and faith made the accomplishment of this thesis possible. With all my love this is for you. iii ACKNOWLEDGMENTS I would like to express my sincere gratitude to my advisor Dr. Timothy Harrigan for all the support, patience, motivation and knowledge during my Master’s program. I am thankful for the opportunity provided to me by Dr. Harrigan and the Department of Biosystems and Agricultural Engineering to obtain my degree. Besides my advisor, I would like to thank my coadvisor Dr. Amirpouyan Nejadhashemi for all the continuous help, support and enthusiasm. I have learned so much from both Dr. Harrigan and Dr. Nejadhashemi, and I am very grateful to have had their guidance. I would like to extend my sincere thanks to my thesis committee members, Dr. Steven Safferman and Dr. Santiago Utsumi, for their encouragement and insightful comments. I would also like to thanks Dr. Katherine L. Gross, M.S. Mathew Haan, Jim Bronson, Howard Straub, Dr. Dana Kirk and Dr. Alan Rotz for their technical knowledge and support during the development of my research. I would never have been able to finish my research without the help from the dairy farmers who provided very useful information; the support from M.S. Faith Cullens and PhD candidate Edwin Martinez (USDA-NRCS) who helped me connect with the farmers. Furthermore, I would like to thank the Kellogg Biological Station, the Department of Biosystems and Agricultural Engineering and the Merle and Catherine Esmay Scholarship for providing financial support. And last but not least, I would like to express my profound gratitude to my family and friends who morally supported me and believed in me. My greatest appreciation is for my husband for his support, advice, motivation, love, faith and patience in every moment of my graduate study. This study would not have been possible without all of your help. iv TABLE OF CONTENTS LIST OF TABLES ......................................................................................................................... ix LIST OF FIGURES ..................................................................................................................... xiv KEY TO SYMBOLS AND ABBREVIATIONS ......................................................................... xv CHAPTER 1: INTRODUCTION ................................................................................................... 1 1.1. Objectives ............................................................................................................................. 5 CHAPTER 2: LITERATURE REVIEW ........................................................................................ 6 2.1. Confinement Dairy Farms .................................................................................................... 7 2.2. Pasture-based Dairy Farms................................................................................................... 7 2.2.1. Characteristics of pasture-based dairy systems ............................................................. 9 2.3. Transition from confinement to a pasture-based dairy....................................................... 10 2.4. Anaerobic Digestion ........................................................................................................... 11 2.4.1. Feedstocks for anaerobic digestion.............................................................................. 12 2.4.2. Byproducts ................................................................................................................... 14 2.4.2.1. Biogas .................................................................................................................. 14 2.4.2.1.1. Temperature .................................................................................................. 14 2.4.2.1.2. pH.................................................................................................................. 15 2.4.2.1.3. Retention Time.............................................................................................. 15 2.4.2.1.4. Solids concentration ...................................................................................... 16 2.4.2.1.5. Nutrient requirements and carbon/nitrogen ratio .......................................... 16 2.4.2.1.6. Mixing of the digesting material ................................................................... 17 2.4.2.1.7. Food to microorganism ratio ......................................................................... 18 2.4.2.1.8. Biogas use ..................................................................................................... 18 2.4.2.2. Digestate .............................................................................................................. 20 2.4.2.3. Reduce greenhouse gas emission ......................................................................... 22 2.4.3. Overall benefits and disadvantages of anaerobic digestion ......................................... 23 2.4.4. Types of Anaerobic Digester ....................................................................................... 24 2.4.4.1. Plug Flow Digester .............................................................................................. 26 2.4.4.2. Complete-mix Digester ........................................................................................ 26 2.4.4.3. Covered Lagoon ................................................................................................... 27 2.4.5. Dairy Manure Digester ................................................................................................ 27 2.4.5.1. Capital cost........................................................................................................... 30 2.4.5.2. Electricity ............................................................................................................. 35 2.4.5.3. Biomethane .......................................................................................................... 36 2.4.5.4. Heat ...................................................................................................................... 37 2.4.5.5. Digested solids ..................................................................................................... 37 2.4.5.6. Carbon-credits ...................................................................................................... 38 2.4.6. Regulations .................................................................................................................. 39 2.4.6.1. Federal Regulations related to Anaerobic Digestion ........................................... 40 v 2.4.6.1.1. Air regulations .............................................................................................. 40 2.4.6.1.2. Solid Waste regulations ................................................................................ 41 2.4.6.1.3. Water regulations .......................................................................................... 41 2.4.6.2. Michigan permitting requirements related to Anaerobic Digestion .................... 41 2.4.6.2.1. Air permits .................................................................................................... 41 2.4.6.2.2. Solid waste permits ....................................................................................... 42 2.4.6.2.3. Water permits ................................................................................................ 42 2.5. Systems Modeling and Simulation..................................................................................... 42 2.5.1. Crop models ................................................................................................................. 44 2.5.2. Farm economic models ................................................................................................ 45 2.5.3. Farm environmental and animal models ..................................................................... 45 2.5.4. Whole farm simulation models.................................................................................... 46 2.5.1. Integrated Farm System Model ................................................................................... 46 CHAPTER 3: PROCEDURE ....................................................................................................... 49 3.1. Representative farm development ...................................................................................... 52 3.1.1. Type of dairy farm ....................................................................................................... 52 3.1.2. Cattle frame ................................................................................................................. 53 3.1.3. Land base ..................................................................................................................... 54 3.1.4. Milk production ........................................................................................................... 54 3.1.5. Type of Manure Treatment .......................................................................................... 55 3.2. Herd and crop information of representative farms ........................................................... 63 3.3. Tillage and planting information ........................................................................................ 67 3.4. Economic information ........................................................................................................ 71 3.5. Pasture growth and management........................................................................................ 74 3.6. Crop nutrient requirements, nutrient availability and loss ................................................. 77 3.8. Anaerobic digestion............................................................................................................ 79 3.9. Environmental impacts ....................................................................................................... 82 CHAPTER 4. RESULTS AND DISCUSSION ............................................................................ 86 4.1. Comparison of farm performance and resource use........................................................... 86 4.1.1. Milk, feed and manure production .............................................................................. 87 4.2. Economics .......................................................................................................................... 90 4.2.1. Manure handling costs ................................................................................................. 91 4.2.2. Production costs ........................................................................................................... 93 4.2.3. Income and net return .................................................................................................. 96 4.3. Environmental impact ........................................................................................................ 98 4.3.1. On-farm nutrient cycling ............................................................................................. 98 4.3.2. Confinement systems ................................................................................................. 101 4.3.2.1. On-farm nutrient cycling.................................................................................... 101 4.3.2.1.1. Potassium .................................................................................................... 103 4.3.1.1.2. Nitrogen ...................................................................................................... 104 4.3.1.1.3. Phosphorus .................................................................................................. 104 4.3.2.2 .Environmental emissions ................................................................................... 105 4.3.2.2.1. Carbon dioxide and methane emissions ...................................................... 105 vi 4.3.2.2.2. Ammonia emissions .................................................................................... 107 4.3.2.2.3. Nitrous oxide emission ............................................................................... 108 4.3.2.2.4. Hydrogen sulfide emissions ........................................................................ 109 4.3.2.3. Environmental footprints ................................................................................... 110 4.3.2.3.1. Water footprint ............................................................................................ 111 4.3.2.3.2. Energy footprint .......................................................................................... 112 4.3.2.3.3. Reactive nitrogen loss footprint .................................................................. 113 4.3.2.3.4. Carbon footprint .......................................................................................... 114 4.3.3. Seasonal pasture farms .............................................................................................. 115 4.3.3.1. On-farm nutrient cycling.................................................................................... 115 4.3.3.1.1. Potassium .................................................................................................... 116 4.3.3.1.2. Nitrogen ...................................................................................................... 116 4.3.3.1.3. Phosphorous ................................................................................................ 119 4.3.3.2. Environmental emissions ................................................................................... 119 4.3.3.2.1. Carbon dioxide and methane emissions ...................................................... 120 4.3.3.2.2. Ammonia emissions .................................................................................... 121 4.3.3.2.3. Nitrous oxide emissions .............................................................................. 122 4.3.3.2.4. Hydrogen sulfide emissions ........................................................................ 123 4.3.3.3 Environmental footprints .................................................................................... 124 4.3.3.3.1. Water footprint ............................................................................................ 124 4.3.3.3.2. Energy footprint .......................................................................................... 125 4.3.3.3.3. Reactive nitrogen loss footprint .................................................................. 126 4.3.3.3.4. Carbon footprint .......................................................................................... 126 4.3.4. Annual Pasture-based farm ........................................................................................ 126 4.3.4.1. On-farm nutrient cycling.................................................................................... 126 4.3.4.1.1. Potassium .................................................................................................... 127 4.3.4.1.2. Nitrogen ...................................................................................................... 127 4.3.4.1.3. Phosphorous ................................................................................................ 127 4.3.4.2. Environmental emissions ................................................................................... 128 4.3.4.2.1. Carbon dioxide and methane emissions ...................................................... 128 4.3.4.2.2. Ammonia emissions .................................................................................... 129 4.3.4.2.3. Nitrous oxide emissions .............................................................................. 129 4.3.4.2.4. Hydrogen sulfide emissions ........................................................................ 129 4.3.4.3 Environmental footprints .................................................................................... 130 4.3.4.3.1. Water footprint ............................................................................................ 130 4.3.4.3.2. Energy footprint .......................................................................................... 130 4.3.4.3.3. Reactive nitrogen loss footprint .................................................................. 131 4.3.4.3.4. Carbon footprint .......................................................................................... 131 CHAPTER 5: CONCLUSIONS ................................................................................................. 132 CHAPTER 6: SUGGESTIONS FOR FUTURE RESEARCH ................................................... 136 APPENDICES ............................................................................................................................ 137 vii APPENDIX A: DATA COLLECTED FROM FARM VISITS ON CONVENTIONAL CONFINEMENT DAIRIES ................................................................................................... 138 APPENDIX B: DATA COLLECTED FROM FARM VISITS ON SEASONAL PASTURE AND PASTURE-BASED DAIRIES ...................................................................................... 143 APPENDIX C: DATA SELECTED FOR THE FIVE REPRESENTATIVE DAIRY PRODUCTION SYSTEMS .................................................................................................... 155 APPENDIX D: RESULTS FROM IFSM OF THE FIVE REPRESENTATIVE DAIRY PRODUCTION SYSTEMS .................................................................................................... 172 REFERENCES ........................................................................................................................... 186 viii LIST OF TABLES Table 1. Estimated manure characteristics as excreted (ASABE, 2008) ...................................... 17 Table 2. Composition of Biogas from the Anaerobic Digestion of Dairy Manure....................... 19 Table 3. Summary of Characteristics of Digester Technologies (EPA, 2004) ............................. 25 Table 4. Summary of process attributes (Burke, 2001) ................................................................ 25 Table 5. Expected percentage VS conversion to gas (Burke, 2001) ............................................. 26 Table 6. Matching a Digester to a Dairy Facility (EPA-AgSTAR, 2004) .................................... 29 Table 7. Characteristics of lactating dairy cow manure and biogas potential (ASABE, 2005) .... 30 Table 8. Investment required for similar or any dairy operation with 160 milking cows (Lazarus, 2009) ............................................................................................................................................. 34 Table 9. Economic analysis of the digester (Lazarus, 2009) ........................................................ 35 Table 10. Estimated values for the seasonal pasture dairy with 142 medium-frame Holsteins, anaerobic digestion, imported manure and additional land for cash crop production. ................. 59 Table 11.Major descriptive parameters of five representative dairy production systems ............ 64 Table 12. Major machines and structures used for planting and manure storage for five representative dairy production systems ....................................................................................... 69 Table 13.Major machines and structures used for crop harvest and storage on the five representative dairy production systems ....................................................................................... 71 Table 14. Major dairy costs ($/cow-year) ..................................................................................... 73 Table 15. Economic parameters and prices assumed for five representative dairy production systems .......................................................................................................................................... 73 Table 16. Grazing parameters for the seasonal and annual pasture systems ................................ 76 Table 17. Anaerobic digester parameters...................................................................................... 81 ix Table 18. Average annual milk, feed and manure production of five representative dairy production systems........................................................................................................................ 88 Table 19. Manure handling costs ($/year) for five representative production systems ................ 92 Table 20. Total production costs ($/year) for five representative dairy production systems ....... 93 Table 21. Income and net return to management and unpaid factors ($/year) for five representative dairy production systems ....................................................................................... 97 Table 22. Land area of five representative dairy production systems (ha) ................................. 101 Table 23. Annual nutrient cycling on five representative dairy farms. ...................................... 102 Table 24. Nutrient loss to the environment on five representative dairy farms (kg/ha-yr). ....... 102 Table 25. Environmental emissions of five representative dairy production systems ................ 105 Table 26. Biogenic carbon dioxide emissions of five representative dairy production systems (kg/yr) ......................................................................................................................................... 106 Table 27. Methane emissions of five representative dairy production systems (kg/yr) ............. 107 Table 28. Ammonia emissions of five representative dairy production systems (kg/yr) ........... 108 Table 29. Nitrous oxide emissions of five representative dairy production systems (kg/yr) ..... 109 Table 30. Hydrogen sulfide emissions of five representative dairy production systems (kg/yr) 110 Table 31. Water footprints of five representative dairy production systems .............................. 111 Table 32. Energy footprint of five representative dairy production systems .............................. 112 Table 33. Reactive nitrogen loss footprint of five representative dairy production systems ...... 114 Table 34. Carbon footprint of five representative dairy production systems ............................. 115 Table A. 1. Land information collected from confinement farm…………………………... 139 Table A. 2. Crop information collected from confinement farm ................................................ 139 Table A. 3. Animal information collected from confinement farm ............................................ 139 Table A. 4. Livestock expenses information collected from confinement farm ......................... 140 x Table A. 5. Animal feeding information collected from confinement farm ............................... 140 Table A. 6. Animal facilities information collected from confinement farm ............................. 141 Table A. 7. Manure information collected from confinement farm ........................................... 141 Table A. 8. Storage structures information collected from confinement farm ........................... 142 Table B. 1. Land information collected from seasonal pasture and pasture-based farms…. 144 Table B. 2. Crop information collected from seasonal pasture and pasture-based farms ........... 145 Table B. 3. Animal information collected from seasonal pasture and pasture-based farms ....... 146 Table B. 4.Livestock expenses information collected from seasonal pasture and pasture-based farms ........................................................................................................................................... 146 Table B. 5. Animal feeding information collected from seasonal pasture and pasture-based farms ..................................................................................................................................................... 147 Table B.6. Animal facilities information collected from seasonal pasture and pasture-based farms ..................................................................................................................................................... 148 Table B. 7. Manure information collected from seasonal pasture and pasture-based farms ...... 148 Table B. 8. Storage structures information collected from seasonal pasture and pasture-based 150 Table B. 9. Economic information collected from seasonal pasture and pasture-based farms .. 151 Table B. 10. Grazing information collected from seasonal pasture and pasture-based farms .... 152 Table B. 11. Data for calculations for fence investments ........................................................... 153 Table B. 12. Data for calculations for investment in watering system ....................................... 154 Table C. 1. Representative farms…………………………………………………………... 156 Table C. 2. Land information selected for farms F1, F2, F3, F4, F5, F6 .................................... 156 Table C. 3. Crop information for farms F1, F2, F3, F4, F5, F6 .................................................. 157 Table C. 4. Grazing information for farms F3, F4 and F5 .......................................................... 158 Table C. 5. Animal information for farms F1, F2, F3, F4, F5, F6 .............................................. 159 Table C. 6. Animal feeding information for farms F1, F2, F3, F4, F5, F6 ................................. 160 Table C. 7. Animal facilities information for farms F1, F2, F3, F4, F5, F6 ............................... 160 xi Table C. 8. Manure information for farms F1, F2, F3, F4, F5, F6 ............................................. 161 Table C. 9. Storage structure information for farms F1, F2, F3, F4, F5, F6............................... 162 Table C. 10. Machine information for farms F1, F2, F3 and F4 ................................................ 163 Table C. 11. Machine information for farms F5 and F6 ............................................................. 164 Table C. 12. Miscellaneous information for farms F1, F2, F3 and F4 ....................................... 165 Table C. 13. Miscellaneous information for farms F5 and F6 .................................................... 166 Table C. 14. Tillage and planting information for farms F1, F2, F3, F4, F5, F6 ....................... 167 Table C. 15. Corn harvest information for farms F1, F2, F3, F4, F5, F6 ................................... 167 Table C. 16. Alfalfa harvest information for farms F1 and F2 ................................................... 168 Table C. 17. Alfalfa and grass harvest information for farms F3 and F4, F5 ............................. 169 Table C. 18. Alfalfa harvest information for farm F6................................................................. 170 Table C. 19. Hauling costs for imported manure in seasonal pasture system (F4) ..................... 171 Table D. 1. Development of seasonal pasture farm with 142 medium-frame Holsteins, cash crop, imported manure and AD…………………………………………………...……………….173 Table D. 2. Average postharvest yield for crops of F1, F2, F3, F4, F5 ...................................... 176 Table D. 3. Annual feed production and utilization of F1, F2, F3, F4, F5 (Average) ................ 176 Table D. 4. Nutrients available, use and lost to the environment of F1, F2, F3, F4, F5 (Average) ..................................................................................................................................................... 177 Table D. 5. Annual manure production, nutrient availability and handling cost of F1, F2, F3, F4, F5 (Average) ............................................................................................................................... 178 Table D. 6. Annual crop production, feeding costs and net return over those costs of F1, F2, F3, F4, F5 (Average) ......................................................................................................................... 179 Table D. 7. Annual production costs and net return to management of F1, F2, F3, F4, F5 (Average) .................................................................................................................................... 180 Table D. 8.Crop production costs and feed costs of F1, F2, F3, F4, F5 (Average) .................... 181 Table D. 9. Annual emissions of important gaseous compounds of F1, F2, F3, F4, F5 (Average) ..................................................................................................................................................... 182 xii Table D. 10. Table of environmental footprints of water, nitrogen, energy and carbon for F1, F2, F3, F4, F5 (Average) ................................................................................................................... 183 xiii LIST OF FIGURES Figure 1. Estimated potential of biogas production from manure co-digested with three different percentages of feedstocks (Norman and Jianguo, 2004). ............................................................. 13 Figure 2. Estimated Annual Emission Reductions from Anaerobic Digestion (EPA, 2012b) ..... 23 Figure 3. Appropriate manure characteristics and handling systems for specific types of biogas production systems (EPA-AgSTAR, 2004). ................................................................................. 28 Figure 4. Capital cost per dairy cow for complete mix, plug flow, and covered lagoon AD systems (EPA-AgSTAR, 2010b) .................................................................................................. 31 Figure 5. Development of five representative dairy production systems ..................................... 58 Figure 6. Anaerobic Digestion in IFSM ....................................................................................... 79 Figure 7. Integrated Farm System Model Overview (USDA, 2013) ............................................ 99 Figure 8. Conceptual model of controls on N gas emissions from soil (modified from Parton et al., 2001) ..................................................................................................................................... 100 Figure 9. Soil phosphorous and potassium build up and depletion ............................................ 103 Figure 10. Nutrients available on farm ....................................................................................... 117 Figure 11. Nutrients crop removal over that available on farm. ................................................. 117 Figure 12. Nitrogen lost to the environment of five representative dairy production systems ... 119 Figure 13. Ammonia emissions of five representative dairy production systems ...................... 121 Figure 14. Nitrous oxide emissions of five representative dairy production systems. ............... 122 Figure 15. Hydrogen sulfide emission of five representative dairy production systems. ........... 124 xiv KEY TO SYMBOLS AND ABBREVIATIONS A Annual pasture-based farm Ac Acres AD Anaerobic Digester ADIAC Anaerobic Digester Initiative Advisory Committee ADIP Acid Detergent Insoluble Nitrogen AEWR Adverse Effect Wage Rate ALFALFA Integrative physiological model of alfalfa growth and development ARS Agricultural Research Service- US Department of Agriculture ASABE American Society of Agricultural and Biological Engineers Avg. Average BIOCOST Bioenergy crop costs BOD Biologic Oxygen Demand Btu British thermal unit °C Celsius degrees C Carbon CAFOs Concentrated Animal Feeding Operations CC Cash crop CERES-Maize Crop Environment Resource Synthesis for corn xv CFR Code of Federal Regulations CH4 Methane CO Carbon monoxide CO2 Carbon dioxide CO2e Carbon dioxide equivalent COD Chemical Oxygen Demand CP Crude protein CS Cool season grass ctw Hundredweight CWT-EQ Hundredweight equivalent DAFOSYM Dairy Forage System Model DairyGem Dairy Gas Emissions Model DGAS Dairy Greenhouse Gas Abatement Calculator DHIA Dairy Herd Information Association Dif. Difference DM Dry matter DNDC Denitrification-Decomposition model em. Emission EPA Environmental Protection Agency xvi EPIC Erosion-Productivity Impact Calculator Ext. Extension F Farm FAO Food and Agricultural Organization FARMSIM Farm Income Simulator FPCM Fat and Protein Corrected Milk ft Feet gal Gallons GHG Greenhouse Gas Emissions GLYCIM Soybean Crop Simulator Gov. Government h Hours H2 Hydrogen H2O Water H2S Hydrogen Sulfide ha Hectares hp Horse power HRT Hydraulic Retention Time IEA International Energy Agency xvii I-FARM Integrated crop and livestock production and biomass planning tool IFSM Integrated Farm System Model in Inches IPCC Intergovernmental Panel on Climate Change IRS Internal Revenue Service K Potassium kg Kilogram kJ Kilojoule km Kilometer kW Kilowatt L Legume LAM Livestock Analysis Model lb Pound m 3 Cubic meter MBtu One thousand British thermal unit Mcal Megacalorie MDEQ Michigan Department of Environmental Quality MI Michigan min Minutes MJ Megajule xviii MMBtu Million British thermal unit MSU Michigan State University MUSLE Modified Universal Soil Loss Equation MWh Megawatt hour N Nitrogen N2 Dinitrogen NAASQS National Ambient Air Quality Standards NASS National Agricultural Statistics Service NDF Neutral Detergent Fiber NFIFO Net Farm Income from Operations NH3 Ammonia NH3-N Ammoniacal Nitrogen + NH4 Ammonium NLEAP Nitrate Leaching and Economic Analysis Package NMPs Nutrient Management Plans NOx Nitrogen oxides NPDES National Pollutant Discharge Elimination System NRC National Research Council NRCS Natural Resources Conservation Service - US Department of Agriculture xix P Phosphorous PM Particulate Matter ppm Parts per million S Seasonal pasture farm SRT Solids Retention Time SWAT Solid and Water Assessment tool t Metric tonne TAN Total Ammoniacal Nitrogen TS Total solids U University UDIM United Dairy Industry of Michigan USDA United States Department of Agriculture USDOE United States Department of Energy VS Volatile solids w With yr Year xx CHAPTER 1: INTRODUCTION The United States has 51,481 dairy farms (Hoard’s Dairyman, 2012) and is the primary milk producer in the world (Dairy Co, 2013). The U.S dairy industry is concentrated in the Great Lakes region with 72% of the United States dairy farms in 2012 (Hoard’s Dairyman, 2012). This region is well suited for dairying because forage is abundant and can be stored as winter feed (EPA, 2012a). The Great Lakes region includes five of the top 10 milk producing states in 2012: Wisconsin, New York, Pennsylvania, Minnesota and Michigan (NASS, 2013). The Michigan dairy industry contributes $14.7 billion to the state economy (UDIM, 2013). According to the USDA, 98% of United States dairy farms are family owned and operated, often by multiple generations (UDIM, 2013). In 2007 there were 9,158 million milk cows on 71,510 operations in the U.S. (Betts and Ling, 2009). These cows produced 84.2 billion kilograms (185.6 billion pounds) of milk along with an estimated 226.8 billion kilograms (500 billion pounds) of manure (Betts and Ling, 2009). Manure processing is routinely handled by collecting, storing and spreading it over the land. Manure contains several essential plant nutrients, such as nitrogen, phosphorous and potassium, which, when is apply correctly, can replace commercial fertilizer applications and increase crop yields. The type of manure and method of application (e.g. broadcast, injected) determine the quantity of nutrient available to the plant (Pennington and VanDevender, undated). There have been frequent complaints related to manure management, odor, and water quality concerns, primarily directed at large livestock operations (Hadrich and Wolf, 2010). Manure-related problems typically occur when liquid manure is spread during the late winter and early spring when manure cannot be tilled in or adequately absorbed by the soil (EPA, 2011). These environmental concerns along with other factors such as the reduction of land base on 1 which to apply manure, the increase in energy costs and growing interest in renewable energy has encouraged farmers to search for alternative manure handling methods (Betts and Ling, 2009). One of the alternatives that produce renewable energy in cost-effective ways is biogas recovery system (U.S Department of Energy, 2012). The use of this technology has been increasingly attractive for manure management with around 30 million anaerobic digesters operating worldwide with manure (Chen et al., 2010). The Michigan Department of Labor and Economic Growth states that this technology is gaining interest because of Michigan new laws regulating odor, potential to reduce groundwater contamination and greenhouse gas production in various parts of the United States (Simpkins, 2005). EPA estimated that there were 188 anaerobic digester operating at commercial livestock farms for biogas recovery in the United States in 2012, and 158 were dairy digester projects (EPA, 2013). The U.S. Environmental Protection Agency (EPA) in 2010 estimated 8,200 U.S. dairy and swine operations produce more than 13 million MWh of electricity with biogas recovery systems. Vanhorn et al. (1994) reported that dairy operations with less than 500 cows produce 3.4 million MWh annually. Anaerobic digesters allow compost and nutrient recovery. A byproduct of biodigesters is a high quality organic fertilizer that can be used in cropping systems. Odors associated with the land application of livestock waste are greatly reduced compared to raw manure (Simpkins, 2005; Zhao et al., 2008). Most dairies that own or contribute manure to biodigesters use the liquid effluent on their own fields (Lake-Brown, 2012). Anaerobic digestion kills several pathogens and effectively reduces biological oxygen demand (BOD) and chemical oxygen demand (COD) in waste, which protects surface waters when the effluent is land applied (EPA, 2005). 2 The emission of CO2 and other greenhouse gases (GHG) has become an important issue. Governments and industries are interested in technologies that will allow more efficient and costeffective waste treatment approaches which will minimize GHG production. Carbon credits will promote the need for CO2 -neutral technologies (IEA Bioenergy, 2006). Anaerobic digestion also impacts farm economics. EPA-AgSTAR (2010b) evaluated the capital costs of dairy farms larger than 500 cows and compared common types of AD systems such as complete mix, plug flow, and covered lagoon. The smallest farm was 500 cows and used a covered lagoon as an anaerobic digester, with a capital cost of about $1600/per cow. A farm with 2,000 cows and a covered lagoon had a capital cost of about $700/per cow and a farm with 4,000 cows and a plug flow digester had a capital cost of about $750/per cow. One of the important factors that influence the feasibility of setting up an anaerobic digester on a dairy production system is how the managers utilize the byproducts (biogas and digestate) (Betts and Ling, 2009). Perhaps the greatest operational challenge in integrating anaerobic digestion and pasturebased dairies is the variable and seasonal supply of feedstock, and the lack of knowledge of how to manage diverse feedstocks in the AD process. There is also a need for further research to make anaerobic digestion byproducts more readily available, cost effective, and manageable to small dairy facilities in the United States. Researchers have created computer models that simulate crop growth, environment and farming systems. Computer models allow the analyst to predict the effect of changes in complex systems (Maria, 1997). Models can help stakeholders understand potential benefits, tradeoffs, costs and impacts associated with management, environmental and other factors (Loucks and Beek, 2005). A model should accurately represent the system and not be too difficult to 3 understand (Maria, 1997). The decision to include or assume information in the model requires judgment, experience, and knowledge about the issues, the system being modeled and the decision-making environment (Loucks and Beek, 2005). The Integrated Farm System Model (IFSM) is a whole-farm simulation model that uses historic weather data to determine long-term farm performance, environmental, and economic impacts of dairy operations. The simulation includes all of the major processes involved in the farming system including crop establishment, crop production, harvest, storage, feeding, milk production, manure handling and the return of manure nutrients back to the land (Rotz et al, 2011a). Recently, a sub-model was added to include on-farm anaerobic digestion. IFSM has been used to compare pasture-based with confinement system dairies. Rotz et al. (2009) used IFSM to compare the predicted environmental impacts of four different dairy operations in Pennsylvania where two of them were confinement dairies and two were rotational grazing systems. They reported that the use of a grazing system could reduce erosion of sediment, runoff of soluble P, the volatilization of ammonia, the net emission of greenhouse gases and the C footprint. However, there is lack of information for evaluating the transition from a confinement system to a pasture-based system, and the feasibility of anaerobic digestion in such systems. Rotz and Hafner (2011b) evaluated the addition of an anaerobic digester on a New York state large confinement dairy farm (1,100 cows) over 25 years of weather. They used farm records to validate simulated feed production and use, milk production, biogas production, and electric generation and use. The digester reduced the net greenhouse gas emissions and farm gate carbon footprint by 25 to 30% with a small increase in ammonia emission. There is a need to 4 evaluate the environmental and economic impact of the integration of an anaerobic digester on a pasture-based system dairy farm with fewer than 500 cows. Belflower et al (2012) evaluated the environmental impact of a management intensive rotational grazing dairy and a confinement dairy in southeastern of United States. They reported that ammonia emissions were higher on the confinement dairy due to manure handling. Greenhouse gas emissions per cow were also higher on the confinement dairy, but the carbon footprint from milk production on the pasture-based dairy was similar to the confinement system which had greater milk production per cow. They concluded that well-managed pasture-based dairy systems have environmental benefits due to reduced erosion and phosphorous runoff, and reduced gas emissions from manure. 1.1. Objectives A comprehensive analysis was conducted using Integrated Farming System Model (IFSM) to evaluate resource use, economics and environmental impacts in the transition from a 100-cow, conventional confinement dairy to an annual pasture-based dairy. Specific objectives were to: 1. Evaluate the operating costs and labor requirements of representative confinement-based and seasonal-and pasture-based systems, including all major interactions from harvest and feeding through manure application, tillage and planting. 2. Compare the economics and performance of an anaerobic digester on representative confinement and seasonal pasture dairies. 3. Compare the environmental impacts of representative confinement, seasonal and annual pasture-based dairies. 5 CHAPTER 2: LITERATURE REVIEW In recent decades many U.S. dairy farms have increased their net income by expanding herd size (Nott, 2003; USDA-NRCS, 2007). This increased the demand for feed and forage and encouraged the use of confinement systems. Large confined herds required larger structures for housing and feed storage and larger handling equipment and waste management systems (USDA-NRCS, 2007). A transition from confinement dairy to pasture-based dairy has been adopted due to the profitability in the dairy industry in the Great Lakes Region (Nott, 2003). Pasture-based dairies can reduce feed, labor, equipment and fuel costs. It provides a lower-cost option for small farmers without expanding their dairy farm, or they can start dairying with less debt (USDANRCS, 2007). Economic studies show that grazing farms can provide satisfactory profits compared with confinement operations. Pasture-based systems generated $887 net farm income from operations (NFIFO) per cow and $4.22 per hundredweight equivalent (CWT EQ), compared to $640 NFIFO per cow and a negative $10 per CWT EQ (Kriegl and McNair, 2005). From an environmental perspective, well-managed pasture-based dairies can reduce erosion and protect water, air, plant and animal resources by maintaining vegetation over the bare soil, increasing soil organic matter, improving water quality (because growing forages trap sediments, fertilizer nutrients, pesticides, animal drugs and pathogens), improving the distribution of nutrients on fields (because waste is more evenly spread) and reducing possible odors, spills, or runoff from animal waste storage areas (USDA-NRCS, 2007; Purdue Extension, undated extension bulletin). 6 2.1. Confinement Dairy Farms USDA-NRCS (2007) defines a confinement-based dairy as one where land use and feed management systems optimize milk production with confined cows consuming harvested forages. In U.S. confinement dairies operations such as manure collection, storage, and land application vary with farm size and cattle housing system (Gourley et al., 2011). Almost all the herd is housed in a free stall or structure system with restricted or no access to pasture. Maternity stalls and calf pens are typically housed in a shed, barn or hutch (Powell et al., 2005). Confinement operations have more control of feed quantity and nutrient concentration during the year which helps to stabilize milk production and nutrient concentrations in manure (Wattiaux and Karg, 2004). Confinement farms tend to import more nutrients than needed by the crops, and nutrient imbalance can result mainly when manure is applied in addition to fertilizer applications in the absence of a regular soil testing program (USDA-NRCS, 2007). 2.2. Pasture-based Dairy Farms USDA-NRCS (2007) defined a pasture-based dairy as a land use and feed management system that optimizes the intake of forages consumed by grazing cows. USDA-NRCS (2007) stated that pasture-based systems are based on two primary resources: pasture, which is a lowcost feed (Soder and Rotz, 2001), and the dairy farmers management skills. Mechanical feed harvesting and storage are reduced because the cow harvests the crop directly from the field. Pasture-based dairies have several benefits. Less purchased feed is required; therefore, fewer acres need to be harvested as stored forage. Producers can also extend the grazing season to fall, winter or spring by using different forage crops (USDA-NRCS, 2007). Typically, in a pasture-based system, forage reaches the rumen as high quality feed (USDA-NRCS, 2007). Vegetative forage is higher in available protein, energy, and essential 7 nutrients than stored forage. Vegetative forage is better than mature grass because grasses tend to build up thicker cell walls once they mature, meaning there are fewer nutrients available for the livestock (Purdue Extension, undated extension bulletin). Seventy to eighty percent of nutrients of consumed feed and forage is returned to land (Whitehead, 1995). The dairy cattle diet, such as supplemental forages and concentrates, needs to maintain a balance of nutrients going out through milk production to reduce fertilizer applications. This maintains fertility levels in the cropland by replacing, with manure or inorganic fertilizer, the nutrients that leave the field in the harvested crop. Between 70 and 90 percent of the phosphorus, potassium, calcium and magnesium consumed by dairy cattle are excreted back onto the pasture (Mott, 1974). Healthier cows with longer productive lives are common on pasture-based dairies. Grazing reduces foot and hoof problems, increases calving percentage, reduces parasite problems, and reduces fly problems (Purdue Extension, undated extension bulletin). Because cows tend to live longer less money is spent on replacement animals and more income is realized from selling heifers (Kriegl and McNair, 2005). Grazing reduces manure handling and odors produced by concentrated manure areas because animals tend to herd less. In pastures, decomposition of manure and undigested feed occurs faster due to the aerobic conditions. In confinement systems, accumulated wet waste can increase the odor problem and ammonia volatilization (Tyrell, 2002). There are many ways to graze, but some of the basic methods include continuous grazing, rotational grazing and management-intensive grazing. In continuous grazing, animals graze in a single large area for the entire season. This is the simplest form of grazing for the farmer in terms of costs and labor. However, this management practice is associated with low forage quality and 8 yield, lower stocking rate, overgrazing and uneven manure distribution (Purdue Extension, undated extension bulletin). Rotational grazing uses more than one pasture so grazing animals can be moved from one pasture to another based on their feed requirements and forage growth. This allows pastures to rest and re-grow, distributes manure more evenly, and increases forage production. The costs of this system are higher than continuous grazing because of the need for water distribution and fencing (Purdue Extension, undated extension bulletin). Management-intensive grazing divides large fields into smaller paddocks so animals can be moved frequently at high stocking rates thereby providing as much of the needed forage as possible from pasture. This type of grazing systems provides the greatest forage production per area, controls weeds and brush naturally, provides the most even manure distribution, gives more forage options, and allows paddocks to rest and regrow completely. The disadvantages are that it requires careful monitoring and greater startup cost for water distribution and fencing (Purdue Extension, undated extension bulletin). 2.2.1. Characteristics of pasture-based dairy systems USDA-NRCS (2007) described the characteristics for an efficient and productive pasturebased dairy system based on practices that optimize livestock performance, pasture quality and dry matter yield and the efficiency of forage utilization. In pasture-based systems, lactating animals are pastured in a way that the entire herd grazes a fresh paddock on alternating days leaving sufficient forage. The animals are on pasture at least 75% of the grazing season and dry cows and heifers are 90%. Lactating animals obtain around 50% of their forage intake during the grazing season and dry cows and heifers obtain around 90%. 9 Every rotation cycle paddocks will vary in size to provide sufficient forage for adequate livestock intake and forage residual to maintain pasture growth. A back fence limits access to the paddocks that where recently grazed by the cows, while a front fence limits the availability of fresh and ungrazed grass. Lanes allow movement between the milk parlor and paddock. Cattle will have available water inside the paddock or in the lane near the paddock in which they are grazing. On average, a cow requires 2 to 2.3 kilograms (4.5 to 5 pounds) of water per day per pound of milk produced (Purdue Extension, undated extension bulletin). A usual rule of thumb is that at least 0.40 ha (one acre) of pasture is necessary for each lactating cow and this area should be within 1.6 km of the milking facility during warm weather. Usually, forage yield will limit herd size (USDA-NRCS, 2007). There are several indicators for assessing the economic success of various systems, but the best indicator is net farm income from operations (NFIFO) per cow or net cost of production per hundred-weight (CWT) of milk produced (USDA-NRCS, 2007). There are some cases where dairy herds exceed 9,072 kilograms (20,000 pounds) of milk per cow per year, and some producers have reported herd averages of 10,866 to 11,784 kilograms (24,000 to 26,000 pounds) of milk per cow per year. However, some pasture-based dairy herds are cost-effective producing 6,804 kilograms (15,000 pounds) of milk per cow per year (USDA-NRCS, 2007). Some obstacles are the types or characteristics of the climate or land base (rough, fragmented terrain, wet soils, heat and humidity or cold weather), which can prevent efficient grazing of dairy cows. 2.3. Transition from confinement to a pasture-based dairy In the transition period from a confinement to pasture-based dairy it is important to take into account all aspects of the major shifts in production and operations. Some of the changes needed to increase efficiency are to improve the milking facilities to reduce milking time; 10 improve pasture fertilization by soil testing and applying recommended fertilizer rates; reduce expensive farm machinery investments; and during the grazing season feed pasture forage based on cattle dry matter intake, amount of standing forage within the paddock, and on forage nutrients (USDA-NRCS, 2007). During the transition from confinement to pasture system there will be a temporary loss of milk production (Kriegl and McNair, 2005) because cows that have never grazed before expect feed that is provided in the barn and they may not know that they will need to graze to obtain feed. However, milk production will increase and meet or exceed their level of production when the cows have learned to graze and maximize dry matter intake from pasture (Purdue Extension, undated extension bulletin). The onset of cold temperatures decreases the forage available for grazing; therefore, more feed needs to be supplemented in the barn and cows need to adjust to eat these feeds again. In general, cows are kept in the barn when nighttime temperatures consistently fall below 4.4 degrees Celsius (40 Fahrenheit). However, if there is forage available, the cows can graze during the day. There are also some farmers that are experimenting with “outwintering” their cattle. In this case, cows would be left out at night to adapt to the colder temperatures and the feed is brought to them (Purdue Extension, undated extension bulletin). 2.4. Anaerobic Digestion Anaerobic digestion (AD) is a process where anaerobic bacteria degrade organic materials in an oxygen free environment to create biogas (mix of methane and carbon dioxide), which can be used to produce electricity and heat (Burke, 2001). The use of anaerobic digesters in the U.S started during 1970’s energy crisis. In 1972, a farm near the town Mt. Pleasant, Iowa, was one of the first farms of U.S. to install an anaerobic digester (Mattocks and Wilson, 2005). 11 Because of federal incentives, by the 1980’s there were already 120 agricultural digesters (Center for Climate and Energy Solutions, 2011), but economic issues and technical problems led to a 60% failure rate of those digesters (Bishop and Shumway, 2009). In recent years, new incentives (grants and loan guarantees) and policies (in the form of renewable electricity standards) have helped increase the use of agricultural anaerobic digesters. EPA-AgSTAR (2011b) estimated 176 digesters were in operation in the United States for livestock manure and many of them were new. The number of digesters in use has been increasing gradually for more than a decade with an average of 16 new digesters each year (AgSTAR, 2011b). 2.4.1. Feedstocks for anaerobic digestion The input for an anaerobic digester is biomass, such as manure, agricultural waste, and urban waste, though they are not similarly degraded or converted to gas (Burke, 2001). Codigestion uses a mix of different feedstocks. The use of animal manure as a feedstock for AD is widespread because it produces a valuable fertilizer as well as biogas (IEA Bioenergy, 2006). Flowing, uniform manure slurry collected daily on a regular schedule is ideal, but pre-treatment may be required to adjust the amount of solids in the manure to meet the requirements of the digester (Betts and Ling, 2009). Digestion transforms the content of manure. There are small reductions in the total of volume of manure due to saturation of the biogas leaving the reactor with water vapor, but this reduction is negligible (EPA-AgSTAR, 2011a). What make digesters helpful are the changes in manure properties and solids separation (Simpkins, 2005). This reduces undesirable odors (Simpkins, 2005) and most nutrients are transformed from an organic form to an inorganic form. The nutrients in manure improve crop yields by converting nitrogen to ammonium, a more readily available form for plant uptake (Betts and Ling, 2009; Lansing et al., 2008). Some studies 12 have shown that crop yields are equivalent to but not greater than those with non-digested manure (Allan et al., 2003; Möller and Müller, 2012). Instead of using only one type of biomass a mix of different types of biomass can be used. An advantage of co-digestion is an increase in different types of feedstocks that can be used for stakeholders that want to increase their biogas yield (The Minnesota Project, 2010). Although animal manure is a very well-known feedstock for anaerobic digesters, it produces a small amount of biogas per kilogram of biomass compared to other type of feedstocks (Biogas Energy Inc, 2008 ). The main problem with co-digestion is creating the right mix of feedstock based on availability and location so that the cost of transport of the feedstock is not higher that the profits due to the co-digestion (The Minnesota Project, 2010). Typical dairy waste biogas is 55 to 65% methane and 35 to 45% carbon dioxide with some trace quantities of hydrogen sulfide and nitrogen (Burke, 2001). If animal waste and other organic feedstock are combined in the right way biogas production may increase anywhere from 200 to 500% (El-Mashad and Zhang, 2007). Figure 1 shows the estimated potential of biogas production from manure co-digested with three different percentages of feedstocks. 7 Biogas potential (m3/cow/day) 6 5 100% manure 4 75% manure and 25% food waste 3 2 50% manure and 50% food waste 1 0 Figure 1. Estimated potential of biogas production from manure co-digested with three different percentages of feedstocks (Norman and Jianguo, 2004). 13 An additional benefit of co-digestion of organic wastes is that with the right combination of different organic wastes the amount of nutrients in the digestate can be optimized to create an effective fertilizer (EPA, 2005). 2.4.2. Byproducts Outputs of anaerobic digestion are biogas and digestate. Biogas is available to heat the digester and potentially satisfy other farm energy needs and sometimes provide energy for export. Another byproduct is the digestate which can be divided into solid and liquid components using a separator and can be used as a fertilizer (Burke, 2001). 2.4.2.1. Biogas The environment in the digester and the feedstock characteristics will affect the rate of conversion of biomass to biogas (Betts and Ling, 2009). Several factors can affect the rate of digestion and biogas production including temperature, pH, retention time, solids concentration, nutrient levels and carbon/nitrogen ratio, food to microorganism ratio, mixing of the digesting material and the particle size of the material being digested (Burke, 2001). 2.4.2.1.1. Temperature In terms of overall system cost and reliability, medium-high temperatures are best (mesophilic temperature range 35°C- 40.5°C) (Simpkins, 2005). The mesophilic process is more tolerant to changes in feed materials or temperature. In the thermophilic range (50°C - 60°C) decomposition and biogas production occurs faster than in the mesophilic range but the process is less tolerant of changes. Biodigester temperature must be kept constant to optimize the digestion process (U.S Department of Energy, 2012). The U.S Department of Energy (2012) reported that anaerobic bacteria can tolerate temperatures from below freezing to more than 57.2°C. Because methane bacteria are naturally 14 widespread in the environment, anaerobic degradation can be achieved at moisture contents from around 50% to more than 99% but they operate best at temperatures of about 36.7°C (mesophilic) and 54.4°C (thermophilic) (IEA Bioenergy, 2006). 2.4.2.1.2. pH The importance of pH in a digester is that it maintains the production and balance of methanogenic and acetogenic, or acetate-producing organisms. Chynoweth and Isaacson (1987) reported that the optimal pH for anaerobic digestion was between 7.0 and 8.0. The pH of manure is at 7.0 or slightly above (USDA, 2003). Methanogenic microorganisms require a pH between 6.8 and 8.5 to produce methane (Burke, 2001). Acid forming bacteria typically grow more rapidly than methane forming bacteria, creating an excess of acid (low pH) in the system and inhibiting the activity of methane forming bacteria. Methane production may stop completely, but if it is maintained a large amount of methane producing bacteria these pH instability could be prevented (Burke, 2001). 2.4.2.1.3. Retention Time Retention time determines reactor volume and maintenance of biological reactions. Hydraulic retention time (HRT) is the time a volume of influent remains in a digester. Solids retention time (SRT) is the length of time solids spend inside a digester and is the most important factor regulating the conversion of solids to gas and maintenance of digester stability (Burke, 2001). Volatile solids (VS) are the basis for estimating organic composition and determining retention times. The degradation of VS in manure increases logarithmically with SRTs greater 15 than approximately 10 days. After approximately 30 days, VS destruction increases linearly until a maximum of 65 percent VS conversion to gas is achieved (Burke, 2001). The SRT and HRT are equal when the digesters do not have digestate solid/liquid separation, followed by recirculation (Burke, 2001). If the SRT is too low, the rate of microbial loss exceeds the rate of growth, causing a “wash out” and a low level of biogas production (Burke, 2001). If the SRT is high the AD must have a larger digester volume, increasing the ability to dilute toxic compounds and allowing more time for microbes to adapt to toxic compounds (Gerardi, 2003). 2.4.2.1.4. Solids concentration Biogas production depends on the solids concentration of the feedstock when the digester is operating close to the optimum retention time (Wheatley, 1990). Lower VS concentrations require a longer SRT for effective biogas production (Chynoweth and Isaacson, 1987). Water content of raw biomass must be measured constantly because digestion of material with total solid content lower than 5% is usually not feasible (EPA, 2005) but some dilution can have positive effects. Water can dilute the concentration of some components such as nitrogen and sulfur from which ammonia and hydrogen sulfide can be produced and inhibit the anaerobic digestion process (Burke, 2001). 2.4.2.1.5. Nutrient requirements and carbon/nitrogen ratio Carbon (C), nitrogen (N), and phosphorus (P) are macronutrients present in dairy cattle manure needed for production of methanogens. ASABE (2008) presents typical macronutrient values for as-excreted dairy lactating cow manure (Table 1). Chen and Hashimoto (1978) reported an optimal C to N ratio of 23:1 for methane forming microorganisms and Archer (1985) 16 reported an optimal C to P ratio of 100-150:1. Iron, nickel, and sulfur, used in the reaction of acetate to methane, are the most important micronutrients required for production of methanogenic microorganisms. Other nutrients of importance needed in limited quantities, are selenium, barium, calcium, magnesium and sodium (Gerardi, 2003). Table 1. Estimated manure characteristics as excreted (ASABE, 2008) Characteristic Dairy Lactating Cow Units Total solids 8.9 kg / day Volatile solids 7.5 kg / day COD 8.1 kg / day BOD 1.3 kg / day Nitrogen 0.45 kg / day P 0.078 kg / day K 0.103 kg / day Total Manure 68 kg / day Total Manure 68 liter / day Moisture 87 % w.b. 2.4.2.1.6. Mixing of the digesting material Mixing of the biomass during the digestion process can aid biogas production (U.S Department of Energy, 2012). Bedding mixed with manure can inhibit anaerobic digestion by reducing biogas production potential. Bedding increases bulk densities within digesters with materials that do not digest very well. The mass transfer within the digester will decrease and required mixing energies will increase, both of which reduce the overall performance of the digester (Arora, 2011). Sands and silts cause problems by clogging pipes, damaging equipment, and accumulating in anaerobic digestion tanks (Burke, 2001). The exception is at low concentrations in a well-mixed digester where the mixing keeps sand in suspension (Burke, 2001), even though the mixer takes up space and increases energy cost (Safferman, personal communication, 2013). 17 2.4.2.1.7. Food to microorganism ratio Food-to-microorganism ratio (F: M) is important because it controls anaerobic digestion. The food-to-microorganism ratio (F: M) is the ratio of kilograms of waste supplied to the kilograms of bacteria available to consume the waste. Depending on temperature, bacteria will consume a limited amount of food per day, so one must supply the proper amount of bacteria to consume the required amount of waste. A lower F: M ratio will convert more quantity of waste to gas (Burke, 2001). 2.4.2.1.8. Biogas use Biogas can be used as a high quality natural gas or as an alternative fuel in engines to generate electricity, boilers to produce hot water and steam, and gas fired absorption chillers used for refrigeration (USDOE, 1996). Gas collected from anaerobic digestion is a combination of methane (CH4), carbon dioxide (CO2), and trace amounts of other gases such as water vapor and hydrogen sulfide (H2S) (Walsh et al., 1988). The typical combination of biogas from a digester with dairy manure is listed in Table 2. Biogas properties influence the choice of technologies for cleaning and utilizing biogas (Yadav et al., 2013). 18 Table 2. Composition of Biogas from the Anaerobic Digestion of Dairy Manure Typical (Percent by volume) 60-70 Methane CH4 30-40 Carbon Dioxide CO 2 Hydrogen Sulfide H2S 300-4,500 ppm Ammonia NH3 Trace Hydrogen (H2) Trace Trace Nitrogen gas (N2) Carbon Monoxide (CO) Trace Trace Moisture (H2O) Other* Trace * Particles, Halogenated hydrocarbons, Nitrogen, Oxygen, Organic silicon compounds, and others (USADA-NCRS, 2009) Each liter of waste processed will produce a quantity of energy depending on the percent conversion of volatile solids to gas. Volatile solids destruction results in methane generation. Each kilogram of volatile solids produces 0.36 cubic meter of methane. Each 0.03 cubic meter (one cubic foot) of methane can produce1055 KJ (1000 Btu) of energy. Therefore, 0.45 kilograms (one pound) of volatile solids will produce 5929 KJ (5620 Btu) of energy. At 35 percent conversion efficiency, the 0.45 kilograms (one pound) of volatile solids will produce 0.58 kWh of energy (Burke, 2001). Biogas can also be used for producing electricity through an internal combustion engine or gas turbine. The engine used produces waste heat (more than 60%) which can be used for heating the facilities, hot water and the digester (EPA, 2005). This generation of heat and power is known as “cogeneration”, which is created from biogas (Betts and Ling, 2009). The biogas can be flared or burned off, but the only advantage is that it breaks down the methane through combustion, reducing methane emissions (Betts and Ling, 2009). However, this option for biogas does not produce revenue for the farm (Binkley, 2010). 19 2.4.2.2. Digestate The non-gaseous material remaining after digestion is referred to as digestate (USDOE, 1996) and can be separated into solid and liquid fractions. Benefits of separating the solids and liquids from digestate include the recovery of bedding, decrease in volume of liquid manure storage, and the ability to sell solid digestate as fertilizer (Sheffield, 2008). The increase in temperature during the digestion process reduces pathogens that are found in waste that accumulates in waste storage facilities (The Minnesota Project, 2010). Solid and liquid components of the digestate can be used as a fertilizer. In the solid portion of digestate most of the P remains and is sold as bulk fertilizer. The liquid portion retains much of the N that is largely converted to ammonium, which is the main component in commercial based fertilizers (The Minnesota Project, 2010). Both can be land applied, thereby offsetting commercial fertilizer purchases. Manure from AD seems to reduce phosphorus and micronutrients that are available for plants, but there is no apparent effect on the short-term crop availability under field conditions. Möller and Müller (2012) showed that adding crop and cover crops residues to the anaerobic digestion process increased the total amounts of mobile organic nutrients within the farming system while nitrogen use efficiency was also higher. It is common to use post-digestion solid waste as bedding for animals on the farm because it eliminates most, if not all, of the bedding costs. Most farmers that had used solid digestate as bedding report that is great for cow well-being and is also known to be less vulnerable to disease spreading bacteria, because the digestion process removes most of the digestible organic matter (EPA, 2005). 20 Another benefit of the digestate is odor reduction. Anaerobic digesters can reduce manure odors by 70% to 80% compared to untreated manure (Zhao et al., 2008). Two of the three stages of biogas production are related to odor. During the first stage there can be some undigested materials because some fibrous material cannot be liquefied and other inorganic materials can either accumulate or pass through the digester intact. Undigested materials make up the low-odor in the digestate (Legget et al., undated). In typical liquid manure storage more acid forming bacteria can survive than methane forming bacteria (because of their sensitiveness to the environment), producing more acids that are not converted to biogas. This excess of volatile acids produces a putrid odor (Legget et al., undated). In contrast, during the second stage of the anaerobic digestion process more acids are converted to biogas thereby reducing odor. Digestate can have some changes in composition during the digestion process. One of them is a reduction in solids content, which for manure slurry could be up to 25% with an increase in ash content, because of mineral conservation, decrease of slurry carbon and decrease of organic matter content. However, due to variability in feedstock and digester conditions, the changes can be inconsistent (Scottish Executive Environment and Rural Affairs Department, 2007). There is also an increase in slurry pH (up to 0.5) and ammonium nitrogen content (up to 25%) (Scottish Executive Environment and Rural Affairs Department, 2007). The increase in slurry ammonium-N content could have some environmental impact by increasing emissions of ammonia during post-digestion storage, which could be controlled with storage covers and following application of the digestate on the land. The reduced solids content could improve surface infiltration of the digestate, which could help to conserve nitrogen (Scottish Executive Environment and Rural Affairs Department, 2007). 21 2.4.2.3. Reduce greenhouse gas emission Anaerobic digesters reduce greenhouse gas emission reductions in two ways: 1. The capture and burning of biogas reduces methane emission which else would be released into the atmosphere from the waste management system (ADIAC, 2009). 2. Fossil fuels are displaced due to the use of biogas to generate energy, therefore greenhouse gases emissions (CO2, methane, and nitrous oxide) and other pollutants are avoided (ADIAC, 2009). The overall impact of converting CH4 to CO2 is beneficial. Methane from a digester is destroyed through combustion, and combustion produces CO2 and H2O. Methane is around 25 times more damaging than CO2 in its effect on global warming (IPCC, 2007). EPA (2012b) presents a graph (Figure 2), which shows the annual emission reductions, including both direct reductions and avoided emissions, due to anaerobic digesters since 2000. In total, the combustion of biogas at the digesters prevents the direct emission of about 61,000 metric tons of methane annually (1,278,000 metric tons of CO2 equivalent) (EPA, 2012b). 22 Figure 2. Estimated Annual Emission Reductions from Anaerobic Digestion (EPA, 2012b). For interpretation of the references to color in this and all other figures, the reader is referred to the electronic version of this thesis. 2.4.3. Overall benefits and disadvantages of anaerobic digestion Anaerobic digestion is a natural waste treatment process. It reduces disposed waste volume to be landfilled and it requires less land than aerobic composting (IEA Bioenergy, 2006). EPA (2012b) made a comparison of organic food scrap recycling technologies for a facility processing 40,000 tons per year of organic materials. Anaerobic composting required between 2.4 to 5.3 ha of land area and anaerobic digestion required 1.2 to 2.4 ha. Anaerobic digestion is an energized process. Biogas is used for heat or electrical generation. Waste heat can be used for heating and cooling dairy facilities. The power generated 23 is “distributed power”, which reduces the need to transform the power grid; therefore, the impact of new power on the power grid is decreased (Burke, 2001). The time devoted to handling processed digested manure is reduced compared to raw manure. Nutrients are concentrated into a smaller volume reducing land required for liquid waste application (Burke, 2001). Anaerobic digestion also has an environmental impact by reducing greenhouse gas emissions and odors (IEA Bioenergy, 2006). From each ton of carbon recycled it can be obtained carbon credits (greenhouse gas credits). Revenues can be obtained from the treating imported wastes (tipping fees), the sale of nutrient-rich fertilizer and sanitized bedding, greenhouse gas credits, and the sale of power (Burke, 2001). Anaerobic digestion has some disadvantages such as the need for a high level of capital investment in structures and facilities. Technical knowledge is also required because digesters require proper care, feeding, and good management. At least one person should be in charge of the digester for preventive and unscheduled maintenance, weekly maintenance for oil changes, engine overhauls and periodic digester clean-out. It is important to realize that anaerobic digesters can be a farm safety hazard because of confined space, lack of oxygen and exposure to toxic gas (Legget et al., undated). 2.4.4. Types of Anaerobic Digester Although there are several types of anaerobic digesters, the most common are plug flow systems, complete mix digesters and covered lagoons. The systems are typically well adapted to the individual dairy operation where they are installed. By 2012, EPA had identified 153 anaerobic digester projects utilizing dairy manure in the United States: 79 were plug flow systems, 46 were complete mix digesters and 4 were covered lagoons (EPA, 2012b). Table 3 24 shows a summary of characteristics of digester technologies; Table 4 shows a summary of process attributes and Table 5 shows an expected percentage of volatile solids conversion to gas. Table 3. Summary of Characteristics of Digester Technologies (EPA, 2004) Characteristics Covered Lagoon Complete Mix Plug Flow Fixed Film Digester Digester Round/Square Rectangular InAbove ground Digestion vessel Deep lagoon In/Aboveground tank tank ground tank Level of Low Medium Low Medium technology Supplemental heat No Yes Yes No Total Solids 0.5-3% 3-10% 11-13% 3% Solids Fine Coarse Coarse Very fine characteristics HRT* (days) 40-60 15+ 15+ 2-3 Farm type Dairy, Hog Dairy, Hog Dairy only Dairy, Hog Temperature and Temperature and Optimum location All Climates All Climates warm climates warm climates *Hydraulic Retention Time (HRT) is the average number of days a volume of manure remains in the digester Table 4. Summary of process attributes (Burke, 2001) Attribute Complete Complete mixmixthermo mesophilic Not limited by solids X X concentration Not limited by foreign material X X Digest entire dairy waste stream X X Sand and floating solids X X processing Best at odor control X Treat additional substrate X X Stability Simplicity Flexibility Net energy production X 25 Plug Flow Mesophilic Covered Lagoon X X X X Table 5. Expected percentage VS conversion to gas (Burke, 2001) Process Load Conversion to gas Entire Waste Stream Completely mixed mesophilic High 35 to 45% Completely mixed thermophilic High 45 to 55% Partial Waste Stream Plug mesophilic High 35 to 45% Covered Lagoon Low 35 to 45% 2.4.4.1. Plug Flow Digester A plug flow digester is a long rectangular concrete tank with an air-tight cover where manure flows in one end and out the other with no axial agitation (Betts and Ling, 2009). Some internal mixing does occur because it is filled daily with biomass (Pennsylvania State University, 2009). Theoretically, as one plug of manure is added to the digester, one plug will leave the digester. A fraction of methanogens is displaced with the effluent, therefore part of the waste must be converted to new methanogens because they are not conserved (Burke, 2001). This type of digester is best suited for thicker manure or waste containing a higher percentage of solid material (Pennsylvania State University, 2009). They are subject to stratification, but it can be partially avoided by maintaining a relatively high solids concentration in the digester (Burke, 2001). The digester is ideal for scraped and partially washed manure operations (Wilkie, 2005). 2.4.4.2. Complete-mix Digester The complete mix digester (also referred to as a “continually stirred tank reactor”) heats and mixes the manure in a cylindrical tank for more efficient biogas conversion. Manure is mixed by a motor-driven impeller, pump, or other types of devices. The manure is usually heated in order to maintain a mesophilic or thermophilic environment (Betts and Ling, 2009). Usually, 26 when co-digestion is to be used, a complete mix system is desired, especially when the characteristics of the added waste are different than manure (Totzke, 2009). Scraped or flushed systems that are used to clean barns with water generate slurry manure. Slurry manure contain between three to ten percent of total solids, which works best in complete mix digesters system (Betts and Ling, 2009). Burke (2001) recommended not using manure diluted with parlor or flush water with the thermophilic digestion of dairy because necessary energy will meet the heat requirements. 2.4.4.3. Covered Lagoon Covered lagoon digesters are best suited for extremely dilute manures stored in an anaerobic lagoon. It is essentially a pond with a cover that treats liquid manure consisting of less than 2% solids (Nelson and Lamb 2002). The reaction rate is affected by seasonal temperature variations (Burke, 2001). Odor may not be entirely removed due to incomplete digestion. They are more appropriate for flush manure collection systems with total solids of 0.5 to 3 percent (Betts and Ling, 2009). These systems have long retention times, between 35 and 60 days, and are generally not heated. Anaerobic lagoons in climates with low temperatures are the most inexpensive type of digester (Nelson and Lamb 2002). Thus, they produce more gas in warmer climates but are also used in northern climates to also reduce odors (Pennsylvania State University, 2009). Increasing gas yield is accomplished by mixing or heating a lagoon digester, which increases costs. Periodically, covered lagoons must be cleaned at considerable cost (Burke, 2001). 2.4.5. Dairy Manure Digester Extensive types of manure pretreatment and treatment options are available. Typical pretreatment involves screening and gravity separation of the solids. But it is recommended not 27 to use pretreatment processes before anaerobic digestion because they produce odor, are expensive and impact potential energy generation. However, excess of sands, silts, and fibers should be removed as part of the anaerobic digestion process. Anaerobic treatment is the most effective on minimizing odors, producing fertilizer and/or bedding, producing energy and it also has the lowest operation and maintenance cost (Burke, 2001). Figure 3 shows the manure characteristics and handling systems that are applicable for particular types of biogas production systems. Table 6 can help in matching an anaerobic digester with a facility. The warm and cold climate, described in Table 6, refers to the moderate to warm region below the 40th parallel and the cold region is above the 40th parallel. Figure 3. Appropriate manure characteristics and handling systems for specific types of biogas production systems (EPA-AgSTAR, 2004). 28 Table 6. Matching a Digester to a Dairy Facility (EPA-AgSTAR, 2004) Climate Collection System Estimated Min. %TS Ratio of Water: Manure Flush 10:1 <3% Moderate Scrape and parlor 4:1 – 1.1:1 3% - 11% to warm wash water Scrape manure only N/A >11% Digester Type Covered lagoon Complete mix Plug flow Limited possibility for covered lagoon Flush Cold 10:1 <3% Scrape and Parlor wash water Scrape manure only 4:1 – 1.1:1 3% - 8% Complete mix N/A >11% Plug flow Kirk and Faivor (2011) recommend understanding how site-specific conditions influence the solids characteristics and the biogas potential of the manure. The TS concentration of manure is a key in selection of an appropriate anaerobic digester and it can vary in several ways depending on the type of dairy housing facility and use of bedding and manure collection system. A typical lactating dairy cow can support the production of 1.33 cubic meters (47.1 cubic feet) of biogas per day (Betts and Ling, 2009). Assuming that the biogas contains 65 percent methane, this would mean 1.33 cubic meters (47.1 cubic feet) of biogas per day or 0.62 kg (1.37 lb) of methane per cow per day (Table 7). 29 Table 7. Characteristics of lactating dairy cow manure and biogas potential (ASABE, 2005) Component Units Per cow Weight Kg/day (lb/day) 68. 04 (150.00) 3 3 Volume 0.07 (2.40) m /day (ft /day) Moisture % 87.00 Total solids Kg/day (lb/day) 9.07 (20.00) Total volatile solids Kg/day (lb/day) 7.71 (17.00) Chemical Oxygen Demand Kg/day (lb/day) 8.16 (18.00) Biological Oxygen Demand Kg/day (lb/day) 1.32 (2.90) Nitrogen Kg/day (lb/day) 0.45 (0.99) Phosphorous Kg/day (lb/day) 0.08 (0.17) Potassium Kg/day (lb/day) 0.1 (0.23) [a] 3 3 1.33 (47.10) Biogas production m /day (ft /day) [b] 3 3 0.87 (30.60) Methane production m /day (ft /day) [b] Methane (CH4) Kg/day (lb/day) 0.62 (1.37) Btu Kg/day (lb/day) 14.02 (30.90) [c] [d] 1055 KJ/day (1000 Btu/day) 2.00 kWh Annual kWh per cow Per day 744.00 3 3 [a] 90% of the manure collected; 30% conversion rate of COD of methane; 0.18 m (6.3 ft ) CH4 per lb COD; 65% CH4 in biogas (NRCS) 3 [b] Biogas with 65% CH4 weighing 0.717 kg/m (NRCS). [c] Represents an average biogas with 65% CH4, where CH4 has a heating value of 3 3 35518.4kJ/m (1010 Btu/ft ) CH4 (EPA, 2005). 3 3 [d] 66.6 kWh per 28.3m (1000 ft ) CH4; assuming 25% thermal conversion efficiency and 90% run-time (EPA, 2005). 2.4.5.1. Capital cost The cost of a dairy waste management system involves: housing, collection, preprocessing, anaerobic digestion, energy production, liquid and handling irrigation, and solids disposal. Housing determines the amount of manure collected. Manure can be collected manually, or by automatic scraper, vacuum truck, or flush. Pre-processing (prior to digestion) and post-digestion (concentration of solids after digestion) can be realized by screening and or sedimentation. After digestion, energy is produced with an engine generator or turbine with heat 30 recovery. It is also important to know the quantity of digestate produced, to know the storage size and disposal of liquid waste (Burke, 2001). EPA-AgSTAR (2010b) analyzed AD system capital cost based on quotes for systems designed only for manure in 2003–2009. Data was collected from 40 dairy farms; from which 13 were complete mix digesters systems, 19 plug flow digesters, and 8 covered lagoons. The capital cost for each system includes the cost of the digester, the engine-generator set, engineering design, and installation. In order to analyze costs evenly, they omitted costs of post-digestion solids separation, hydrogen sulfide reduction systems, and utility charges including line upgrades and interconnection equipment costs and fees (EPA-AgSTAR, 2010b) Figure 4 shows while the smallest farm did have the highest cost per cow for the digester ($1,600), the largest farm did not have the lowest cost per cow ($750). Farms with the second and third smallest number of cows had relatively low costs per cow ($700). Figure 4. Capital cost per dairy cow for complete mix, plug flow, and covered lagoon AD systems (EPA-AgSTAR, 2010b). 31 The feasibility of setting up an anaerobic digester on a dairy production system will depend on how the managers use the byproducts (biogas and digestate). The average cost of additional digester equipment include: 1) post-digestion solids separators, 6.4% of total capital costs (range from: 1.5-12%), 2) biogas treatment system, 3.1% of total capital costs (range: 0.36.0%) and 3) estimated utility charges, 5.3% (range: 1.7-13.5%). The engine and generator costs usually account for 40% of project costs (EPA-AgSTAR, 2010b). In the case of small-scale digesters, U.S. EPA does not recommend biogas recovery systems for livestock farms with less than 500 cows. Moser (2011) reported that 200-400 cows were needed for an economically viable digester system. In 2010 the majority (74%) of U.S. dairy farms had less than 100 cows and in 2011, 88% had less than 200 cows, making anaerobic digestion not feasible to most of U.S. dairy farms (U.S. Census Bureau, 2012). Revenue from electricity sales has been profitable for large-scale operations (Nelson and Lamb, 2002), but small-scale digesters are not often profitable due to their dependence on the electricity price and the high cost of infrastructure needed to sell electricity back to the grid (Lazarus and Rudstrom, 2007; Ghafoori and Flynn, 2007). Electrical generation from biogas was not economically viable but the use of biogas to accomplish the heating requirements on-farm was found to be economically feasible in smallscale dairy farms (Bishop and Shumway, 2009). However, Millen (2008) reported on two small dairy farms (130 and 70 cows) in Ontario that were producing electricity and were profitable. The farmers credited their success to receiving additional waste (130 cow farm only), having a buyer for their electricity, and substantial time dedicated to the project development stage. Several studies have found that direct use of biogas can be profitable on smaller farms when the on-farm heating requirements were high enough to regularly utilize all the produced 32 biogas (Bishop and Shumway, 2009). Another motivation for farmers to install an anaerobic digester is the reduction of odor and improvement of air and water quality. A survey of 64 producers across the United States and 10 in California found that both were the main motivation for digester installation (EPA-AgSTAR, 2007). Possibly the biggest economic challenge for small-scale digestion systems is the uncertainty of traditional (e.g. electricity) and non-market factors (e.g. bedding reuse). Stokes et al. (2008) emphasized the lack of quantifiable data on non-market benefits as a major obstacle to widespread anaerobic digestion implementation. Another challenge is the cooperation of the local electrical utility. In many cases this has discouraged dairies from installing digesters that had been planned (Lazarus, 2008). The Minnesota Project, a group funded by EPA-AgSTAR, is searching for solutions for small- and mid-sized dairies. In 2005 they started a feasibility study on the use of the anaerobic digestion technology by scaling it down and still providing financial incentives for farmers to use it. The Minnesota Project evaluated six anaerobic digestion systems designed for confinement dairies between 100 and 300 cows. They concluded that the digester costs, which were between $105,000 and $230,000, were still too high (Goodrich, 2005). The Minnesota Project prepared a case study based on the Jer-Lindy confinement dairy farm in central Minnesota with 97 ha (240 acres) and 160 milking cows producing about 11,356 L (3,000 gallons) per day of manure based on built a small-scale digester with an up-flow tank system with a 124,918 L (33,000 gallon) holding capacity and five-day HRT. The total a cost of the system was $460,000 (Table 8) (Lazarus, 2009). In operation several technical and maintenance issues caused problems: engine failure, computer control system problems and issues with manure handling (Lazarus, 2009). 33 Table 8. Investment required for similar or any dairy operation with 160 milking cows (Lazarus, 2009) Items Investment Digester tank, gen-set and set up $ 267,000 Fan separator $ 36,000 Building costs and concrete $ 33,000 Utility hook up $ 12,000 Flare and boiler $ 13,000 Specific items that vary from operation to operation Tank insulation $ 32,000 Labor $ 15,000 Additional plumbing and electrical work $ 20,000 Pump and agitator $ 22,000 Excavation $ 10,000 Total digester investment $460,000 The economic analysis evaluated the added value by the generator and the projected costs of owning and operating it. The analysis assumed that the system would produce 430 kWh of electricity per day in which 95 kWh was used to run the pumps, digester and fan separation equipment and 335 kWh per day to replace electricity purchases or to sell back to the grid (Table 9). The manure solids from the separator replaced the sand bedding that normally costs around $1,000 per month (Table 9) (Lazarus, 2009). Solids breakdown in the digester was assumed to reduce manure hauling and agitation costs by $2,400 per year. The most liquid fraction of the digestate could be applied at higher rates on less areas and possibly reduce the pumping cost (Table 9). The sale of carbon credits due to the breakdown of methane in the anaerobic digestion process (Table 9) was considered as an additional source of income (Lazarus, 2009). 34 Table 9. Economic analysis of the digester (Lazarus, 2009) Items Sources of value Electricity generated (335 KWh/day x 365 x $0.085/KWh) Bedding ($75/cow) Reduced manure agitation and hauling MN Renewable Energy Production Incentive Carbon credits (around $5.75 per metric ton of CO2 on the Chicago Climate Exchange on 6/12/08) Total annual benefits Project investment Engine overhauls (assume every 3-5 years) Other O&M (2% of investment) and labor (assume 0.3 h/day) Depreciation and interest on digester and mechanicals (20 years life, 6% interest rate) Total annual cost Grant funds (covered 72% of the Project) Project investment net of grants Annualized value of grants amortized over 20 year life Total annual costs net of grants Net return/year over operating and ownership costs Years to payback $/year $10,393 $12,000 $ 2,400 $ 1,834 $ 556 $27,184 $ 1,250 $ 11,390 $ 29,453 $ 42,093 $ 329,900 $ 130,100 $ 16,495 $ 25,598 $ 1,586 11 2.4.5.2. Electricity In Michigan, two anaerobic digesters are producing 16,897 MWh per year, both from a dairy farm with about 3,000 cows feeding the complete mix digester (EPA, 2012b). One cow can produce roughly 14,770 KJ (14,000 Btu) per day (0.00017 MWh). It would require the manure from around 50 cows to produce enough biogas each day for heating one home (Colorado State University, undated). The annual value of avoided electricity purchases or electricity sales may amount to $94 per cow, based on an electricity rate of 12.96 cents per kWh (2012 U.S. Michigan, Large commercial average) and assuming the digester supports the generation of 2 kWh per cow per day (Betts and Ling, 2009). 35 Various arrangements have been used to capture the value of electricity generated by the combustion of biogas from anaerobic digestion of manure. EPA (2004) showed the arrangement for selling on-farm generated electricity: Biogas sales: The electricity produced is owned by the utility which operates the on-farm generator. The dairy digester operation sells biogas to the utility and purchases all electricity needed for dairy operations at retail rates. All electricity sold: The dairy digester operation sells all its biogas-generated electricity to a utility (usually at the utilities avoided cost rate) and purchases all the electricity needed for dairy operations from the utility at retail rates. Surplus electricity sales: The dairy digester operation generates the electricity needed for dairy operations on-farm, and excess of electricity produced is sold to the utility (usually at the utilities avoided cost rate). If the dairy requires any excess of electricity, this will be purchased from the utility at retail rates. Net metering: The dairy farm will purchase only the net difference between the quantity of electricity consumed and the quantity that the dairy digester operation produces. Binkley (2010) concluded that net metering benefits over the other arrangements for herd sizes between 500 to 1,450 cows. The farm would not pay charges related to standby or administration that is based on the capacity of the engine-generator required to produce the electricity. 2.4.5.3. Biomethane Biomethane can be upgraded to natural gas containing more than 95% methane. Biomethane is obtained from gas produced in the digester by removing hydrogen sulfide, moisture, and carbon dioxide, and when treated correctly it can be used as a substitute of natural 36 gas (Krich et al, 2005). Biogas produced in an anaerobic digester usually contains around 40% carbon dioxide, however pipeline quality natural gas contains less than 1% carbon dioxide (EPA, 2005), making the conversion from biogas to natural gas costly (Krich et al, 2005). Biomethane can substitute pipeline quality natural gas which is used for households, commercials or industries (EPA, 2005). However, few projects have upgraded the biogas to pipeline quality and provided methane to a nearby commercial natural gas pipeline (Krich et al, 2005). 2.4.5.4. Heat Almost half of the engine fuel energy can be recuperated with the waste heat which comes from the engine jacket and exhaust gas. This waste heat can be used for maintaining the temperature in the digester, heating farm buildings, water, and/or alley floors. Also waste heat could be used to warm the manure that is entering the digester, reducing the amount of heat used for changing the manure temperature to the optimum digester temperature (EPA, 2005). Avoided fuel purchases for heating will depend on the price of fuel and the ability of the operation to utilize the heat (Betts and Ling, 2009). 2.4.5.5. Digested solids Using digested solids as cow bedding has advantages and disadvantages. An advantage is that it may improve cow health (reduced pathogens) and improve milk production (increased revenue). However, additional equipment and operating costs for separating the digested solids from the effluent are required. In addition, using digested solids as bedding requires operator time to avoid potential mastitis problems leading to higher veterinary expenses and lower milk production and sales (Betts and Ling, 2009). 37 2.4.5.6. Carbon-credits Methane captured from the anaerobic digestion of dairy manure may meet the requirements for carbon credits if it is prevented from escaping to the atmosphere. The global warming potential of methane is equivalent to 25 times that of carbon dioxide (IPCC, 2007). Reducing one metric ton of methane gas emission has the same impact as reducing 25 metric tons of carbon dioxide emissions. Based on 2009 national analysis, the use of methane through anaerobic digesters reduced greenhouse gas emissions by over 1.1 million metric tons of carbon dioxide in U.S (EPA-AgSTAR, 2010a). In the United States, there are several trading mechanisms for buying and selling carbon credits. The transaction could be by private negotiations or trading through formal exchange mechanisms. It could also be by auction through The World Green Exchange, which provides a superior price detection system by enabling buyers and sellers to see what the market will command in real time. 2.4.5.7. Fertilizer Improved fertilizer value (over raw manure) could allow some sales of effluent, and less viable weed seeds potentially lower herbicide costs. The minimal odor of the effluent may allow more flexibility in the timing of land application than for raw manure. This flexibility may afford economic benefits to the dairy operation. 2.4.5.8. Environment Using the AD also reduces the water contamination risk, greenhouse gas emission and the quantity of pathogens. Some firms may be willing to pay the dairy a tipping fee for disposal of their organic waste. However, this additional substrate will require increased management (e.g. handling the substrate) and negotiation (Betts and Ling, 2009). 38 2.4.6. Regulations Odor and water quality complaints accounted for 75% of all complaints related to livestock facilities registered with the Michigan Department of Agriculture (1,289 observations) between 1998 and 2007 (Hadrich and Wolf, 2010). The costs of corrective actions on water quality improvement are significantly higher than odor reductions in dairy farms that incorporate manure. In general, small farms are not required to get a permit unless it is proven that pollutants are discharged to surface water bodies. At that point, farms of any size are required to obtain permits and follow regulations set forth by the Michigan Department of Environmental Quality (MDEQ Rector, 2007). Agriculture impact on greenhouse gases is another important aspect that has been regulated. Carbon dioxide, nitrous oxide and methane are emitted to and/or removed from the atmosphere through agricultural activities. The concentrated animal feeding operations (CAFOs) emit air pollutants that are harmful to public health and damaging the environment. Ammonia emissions from animal agriculture account for about 50% of the total ammonia emissions into terrestrial systems (National Research Council, 2003). In 2007, the dairy sector emitted 1,969 million tonnes CO2e (±26 percent) globally of which 1,328 million tonnes was attributed to milk production (FAO, 2010). Currently, the EPA provides no regulation for air pollution from CAFOs. Federal laws establish minimum standards for the regulation of any activity that causes air pollution. 39 2.4.6.1. Federal Regulations related to Anaerobic Digestion 2.4.6.1.1. Air regulations In general, state permits are required if on-site combustion devices exceed federal emissions limits. EPA-AgSTAR (2012b) presents federal air permitting requirements for: Internal combustion engines: should fulfill federal emission standards (40 CFR Part 89) for non-road engines, which include limits for nitrogen oxides (NOx), hydrocarbons, carbon monoxide (CO), and particulate matter (PM). Steam generating devices: Only for the case of devices built after June 19, 1984 and with a heat capacity over 10.5 million KJ per hour should fulfill federal emission standards which include limits for PM, sulfur dioxide, and NOx (40 CFR Part 60, Subpart Db or 40 CFR Part 60, Subpart Dc). Boilers: Only for the case of devices with a heat capacity over 10.5 million KJ per hour should fulfill National Emission Standards for Hazardous Air Pollutants (40 CFR 63 Subpart DDDD), which include limits for arsenic, cadmium, chromium, lead, magnesium, mercury, and nickel. Additionally the Clean Air Act of 2012 requires EPA to set National Ambient Air Quality Standards (40 CFR part 50) for contaminants harmful to public health and the environment. Therefore EPA's National Ambient Air Quality Standards (NAASQS) states the limits of combustion devices emissions such as ozone, PM, CO, NOx and sulfur dioxide. 40 2.4.6.1.2. Solid Waste regulations Permits for manure solid waste are not required by the federal laws, but in some states the mixing or use of other types of substrates may denominate the anaerobic digester as a waste management facility (EPA-AgSTAR, 2012b). 2.4.6.1.3. Water regulations The discharges by CAFOs are regulated by The Clean Water Act which requires the dairy facilities a National Pollutant Discharge Elimination System (NPDES) permit. Part of the discharges to the U.S waters includes improper land application of manure (EPA-AgSTAR, 2012b). For large CAFOs (more than 700 mature dairy cows), additionally to the NPDES permit a Nutrient Management Plans (NMPs) should be developed and maintained to guarantee correct land application of manure. If smaller farms discharge to water bodies through a manufactured device or through direct contact of the animals, they will also be required to have a NPDES permit and NMPs (EPA-AgSTAR, 2012b). 2.4.6.2. Michigan permitting requirements related to Anaerobic Digestion Individual states have regulations on how farms operate anaerobic digesters. The Michigan Department of Environmental Quality presents air and water quality and solid waste regulations. 2.4.6.2.1. Air permits Anaerobic digesters require an air permit if combustion is occurring onsite and produces more than 0.45 kilogram (1 pound) of sulfur dioxide in an hour or has a heat input capacity greater than 10.5 million KJ per hour, with no difference if organics are included (MDEQ Rector, 2007). 41 2.4.6.2.2. Solid waste permits If the anaerobic digester has only manure as biomass, a solid waste permit would not be required. But if other biomass is added to the digester a permit is needed for composting or land applying the solids (MDEQ Rector, 2007). There are some substrates that do not require a permit if the digester receives less than 20% of the substrate, such as food processing waste, syrup from ethanol production, and grease trap wastes that do not include seepage and fish wastes (Department of Natural Resources and Environment, 2009). 2.4.6.2.3. Water permits If the anaerobic digester is operated with only manure a water permit is not required. But if other types of biomass are added to the anaerobic digester a water permit will be needed for land application. CAFOs with permission must include an anaerobic digester in their nutrient management plan (NMP) (MDEQ Rector, 2007). 2.5. Systems Modeling and Simulation Computer models allow the analyst to predict the effects of changes in complex systems (Maria, 1997). Models can help to access the benefits, tradeoffs, costs and impacts associated with management, environment, and other factors (Loucks and Beek, 2005). A model should accurately represent the system (Maria, 1997). The decision to include or assume information in the model requires judgment, experience, and knowledge about the issues, the system being modeled and the decision-making environment (Loucks and Beek, 2005). Usually, a simulation model is a mathematical representation developed with simulation software (Maria, 1997). Mathematical models include “known variables” or “parameters” and “unknown variables” or “decision variables” to be determined. In mathematical terms the model describes the system being analyzed, and the constraints which are the conditions that the system 42 has to satisfy. Constraints define the system components and their inter-relationships, and the permissible ranges of values of the decision-variables, either directly or indirectly. Typically, there exist many more decision-variables than constraints, therefore, if any feasible solution exists, there may be many solutions that satisfy all the constraints (Loucks and Beek, 2005). Model parameter values can be uncertain; therefore, the relationship between various decision variables and assumed known model parameters may be uncertain. This is important because the output of the model will respond with respect to the parameters and model structures (Loucks and Beek, 2005). The model types can be categorized by simulation process, which depends on the application. The main types of models are those based on simulation period such as discrete and continuous, and the models based on how they were simulated such as deterministic and stochastic. Discrete models advance from event time to event time rather than using a continuously advancing time (Ündeğer, 2008). Continuous models use time-varying interactions among variables (Maria, 1997). Deterministic simulation models use fixed input and output variables (Maria, 1997). The model does not contain probability. Every run result will be the same, but a single run is enough to evaluate the result (Ündeğer, 2008). Stochastic simulation models have at least one probabilistic input or output variable initiated using random numbers (Maria, 1997). Different runs initiated with different random numbers generate different results. This requires multiple runs to evaluate the results (Ündeğer, 2008). No model is perfect. However, modeling and simulation should consider every aspect of a proposed changes; therefore, operating procedures or methods can be explored without the 43 need of experimenting with the real world systems. Models provide understanding of how a system operates; therefore, be able to give predictions about how a system will operate under different scenarios (Ündeğer, 2008). An advantage is a better understanding of interactions within the variables that make up a complex system. Modeling and simulation determines answers to “why” questions by recreating the scene and taking a closer look at what has happened during the run. There can also be answers to “what-if” questions for determining future improvements and new designs to the system (Ündeğer, 2008). Simulation modeling also has disadvantages such as special training for model building and results interpretation, such as determining if an observation is due to system interrelationships or just arbitrariness. It can also be time consuming and expensive. Economizing on resources for modeling and analysis may result in a simulation not detailed enough for the problem and may consume time, effort and money for nothing (Ündeğer, 2008). There are several models that have been developed for crop modeling, farm economics, farm environmental and animal modeling. 2.5.1. Crop models ALFALFA is a dynamic computer simulation model of the growth and development of alfalfa (University of California, 2010). Crop Environment Resource Synthesis (CERES-Maize) is a deterministic model that simulates in a field scale corn growth, soil, water, temperature and soil nitrogen dynamics during one growing season (Ritchie et al., undated). Therefore, CERESMaize predicts the duration of growth, the average growth rates, and the economics related to it (Ritchie et al., 1998). In order to simulate the carbon and nitrogen biogeochemistry in agro-ecosystems the Denitrification-Decomposition model (DNDC) was created. The model predicts crop yield, C 44 sequestration, nitrate leaching loss, and emissions of C and N gases in agro-ecosystems. It was developed by the institute for the Study of Earth, Oceans and Space University of New Hampshire (University of New Hampshire , 2009). GLYCIM is a dynamic soybean simulation model with hour time scale. It uses deterministic simulation of organism-level processes (photosynthesis, transpiration, carbon partitioning, organic growth and development) to predict growth and yield of a soybean crop depending on climate, soil, and management practices (Acock and Trent, 1991). 2.5.2. Farm economic models Some models focus on farm economics such as BIOCOST, which is an EXCEL-based software program that can be used to estimate the cost of producing bioenergy crops in seven U.S regions (Walsh and Becker, 1996). FARMSIM is a simulation model used for projecting the probable economic and nutritional impacts of alternative technologies, farming systems, livestock management programs, marketing arrangements, crop mixes, risk management schemes, and environmental remediation programs on a representative crop/livestock farm (Schaber, undated; Edwards, 2007). 2.5.3. Farm environmental and animal models Livestock models typically focus on management and economics. Gaseous emissions submodels are being added to many livestock models. Livestock Analysis Model (LAM) characterizes cattle and buffalo herds used to produce livestock products: milk, meat, and draft power. LAM evaluates the impact of changes in production, and present and future methane emissions from cattle and buffalo populations (EPA, 2010). The Dairy Gas Emissions Model (DairyGEM) is a process level simulation for estimating ammonia, hydrogen sulfide and 45 greenhouse gas emissions of dairy operations based on climate and farm management (Rotz et al.,2012). 2.5.4. Whole farm simulation models Livestock and cropping systems models are often constrained by geographic location or cropping options. The DairyWise dairy farm model simulates popular feed crops like grazed grasses or corn (Sendich, 2008). The Dairy Greenhouse Gas Abatement Calculator (DGAS) is designed for the Australian climate and is not applicable for the Great Lakes Region (The University of Tasmania, 2013). Whole farm simulation models such as the Integrated Farm System Model (IFSM) and IFARM which integrates crop and animal management components are uncommon (Sendich, 2008). Iowa State University created a whole-farm simulation model called I-FARM, which predicts economic and ecosystem impacts due to farm operations across the United States. The model includes several crops and crop rotations with associated tillage, fertilization, planting, weed control, harvesting, and residue removal. Livestock systems are simulated based on feed intake, growth rate, grazing or confinement options, and manure management systems (Iowa State University, 2010). One of the differences between I-FARM and IFSM is that IFSM integrates anaerobic digestion as a waste management system. 2.5.1. Integrated Farm System Model The Integrated Farming Systems Model (IFSM) is a whole-farm simulation model that has been in development since the early 1980’s and was first known as the Dairy Forage System Model or DAFOSYM. The model operates with a daily time step and includes all major components of the livestock and crop production system including feed production, storage and disappearance, animal performance, manure handling, tillage, and planting operations. In order 46 to make the model more comprehensive it was included the simulation of growth, harvest, and storage of grass, small grain, and soybean, beef production and the option of only crop production (no animals). An anaerobic digestion sub-model (Rotz et al, 2011b) and environmental components such as ammonia volatilization, nitrate leaching, phosphorus runoff, and greenhouse gas emissions were also added (USDA, 2012). The main difference between IFSM and most farm models is that IFSM simulates all major farm components on a process level. This allows the components to link the major biological and physical processes interacting on the farm and is a powerful tool for analyzing the effects of management and new technologies in the context of the whole-farm system (USDA, 2012). IFSM is designed mainly for temperate regions of the northern United States and southern Canada. Belflower (2012) used IFSM to simulate an intensively-managed rotational pasture-based dairy and a confinement fed dairy in the southeastern part of United States. The study evaluated management effects on the environment, such as greenhouse gas emissions, carbon footprint, etc. Rotz et al. (2009) used IFSM to compare the predicted environmental impacts of four different dairy production systems in Pennsylvania and reported that the use of a grazing system could reduce erosion of sediment, runoff of soluble P, the volatilization of ammonia, the net emission of greenhouse gases, and the C footprint. Rotz et al. (2011a) evaluated environmental and economic impact of manure application methods in farming systems in Pennsylvania and reported that shallow disk injection was the most affordable with the lowest environmental influence. Rotz and Hafner (2011b) simulated the addition of an anaerobic digestion on a dairy farm in New York over 25 years of weather. Farm records were used to validate the simulations of feed production and use, milk production, biogas 47 production, and electric generation and use. The anaerobic digester decreased net greenhouse gas emissions and the carbon footprint. The economic analysis showed no direct profits to the producer. 48 CHAPTER 3: PROCEDURE A comprehensive analysis was conducted using the Integrated Farm System Model to describe, evaluate, and compare the economics, resource use and environmental impacts of representative dairy farms transitioning from conventional confinement to a year round pasturebased system and the potential for integration of an anaerobic digester in a small confinement and seasonal pasture dairy. In order to describe, evaluate and compare a range of farming systems, five representative dairy farms were compared using the IFSM model. The representative farms do not describe a specific farm; rather they are designed to reflect common features regarding land base, machine selection, crop production, number of cows and young stock and other key components. The five systems include: 1) conventional confinement system with 100 largeframe Holsteins, 2) conventional confinement system with 100 large-frame Holsteins and an anaerobic digester, 3) seasonal pasture system with 142 medium-frame Holsteins, 4) seasonal pasture system with 142 medium-frame Holsteins, an expanded land base for cash crop production with imported manure and an anaerobic digester and, 5) annual pasture-based system with 160 small-frame New Zealand Friesian cows. The analysis was conducted over 26 years of East Lansing, Michigan weather conditions to obtain a comprehensive analysis of system performance. Based on farm visits (Appendix A and B) and discussions with dairy farmers considering the transition from total confinement to an annual pasture-based system, a herd size of 100 cows is a common tipping point in the decision to continue with total confinement facilities and expand herd size or maintain herd size and begin the transition to a seasonal or annual pasturebased system to reduce operating costs. Total confinement systems typically have large-frame 49 Holsteins bred for high milk production. The initial representative farm for analysis was a milking herd of 100 large-frame Holstein (726 kg mature weight) cows with 80 replacements in conventional confinement housing and a land base of 111 ha (275 ac, 1.11 ha (2.75 ac) per cow). This land base balanced feed produced on the farm with small amounts of purchased or sold forage or grain, and balanced manure nutrient application with crop removal to maintain a near nutrient balance on the farm. In a seasonal pasture system cattle are on pasture during summer growing season and confined during winter. For seasonal pasture systems farmers typically prefer smaller cattle with traits and genetic potential for milk production between the large-frame and small-frame cows, such as medium-frame Holsteins. Smaller frame cattle generally consume less feed and produce less manure than large-frame cattle. Therefore, a seasonal pasture system with 142 mediumframe Holstein cows (590 kg mature weight) with the same land base as the confinement system (111 ha) was evaluated as the representative seasonal pasture farm. The land base was held constant and the cow numbers were increased to maintain the balance between land available for feed production and the nutrient balance on the farm with only small amounts of forage purchased or sold. In an annual pasture-based system, New Zealand Friesian cows (454 kg mature weight) are the typical cattle (similar to a small-frame Holstein) because of their efficient conversion of grass to milk. Cattle are supplemented with some dry hay, round bale silage and a small amount of purchased grain with minimal housing throughout the year. The representative annual pasturebased system had 160 New Zealand Friesian cows with replacements on the 111 ha (275 acre) land base. These cow numbers and land base provided a near balance of feed produced and nutrient use on the farm. 50 Biogas recovery systems on livestock operations can produce renewable energy and provide additional benefits to the farm. Biogas from anaerobic digestion can heat water and potentially satisfy other farm energy needs. The digestate can be used as a fertilizer, and bedding and can be often recovered for reuse. Revenue from electricity generated on-farm can be obtained through biogas and electricity sale, reduction in purchased electricity use, and in some cases, net metering (EPA, 2004). Other revenue may be obtained through carbon credits if methane is captured and prevented from escaping to the atmosphere. The Michigan Department of Labor and Economic Growth reported that this technology is gaining interest because of new laws regulating odor, the potential to reduce groundwater contamination, and concerns about greenhouse gas production (Simpkins, 2005). Currently, a herd size of 500 cows is considered the break-even point for a typical AD system for dairy farms (EPA-AgSTAR, 2010b). In this work, this was confirmed by the addition of an anaerobic digester to the total confinement farm with 100 large-frame Holsteins resulted in an annual reduction of the net return to management and unpaid factors of more than $14,000 per year. When an anaerobic digester was added to a 500-cow, total confinement dairy there was an increase in net return to management and unpaid factors of $9,000 per year. This confirmed that manure from about 500 cows (about 15,600 t/yr) is needed for a break-even investment on a typical dairy farm producing energy for on-farm use with recovered bedding. Seasonal pasture dairies in the Great Lakes region are typically smaller than 500 cows. Additionally, anaerobic digesters require a steady supply of manure throughout the year for efficient use. The expansion of many dairy farms is restricted by the lack of land available for application of manure nutrients. These farms can benefit by exporting manure nutrients for offfarm use. Cropping systems benefit from the nutrients and other soil quality building factors that 51 livestock manure provides. One alternative for the cost effective integration of an anaerobic digester on a small, seasonal dairy may be to import manure from nearby dairies, thereby providing a steady, year round supply of manure in a quantity that is economically feasible. The economics and performance of the representative 142-cow seasonal dairy was evaluated when importing 12,882 wet t of dairy manure from nearby dairies (0.75 miles). This volume of manure, when added to the manure deposited in the barn by the milking herd (2,885 t/yr), provided an annual manure volume similar to that produced on a 500-cow dairy (15,600 t/yr). Additional cash crop land was added to the land base of the seasonal dairy to balance the additional nutrients with crop removal. 3.1. Representative farm development Five representative farms were simulated based on information collected from farm visits (Appendix A and B), literature review and discussions with dairy extension professionals. Appendix C presents the selected information for each farm. These representative farms were selected to provide a near balance between the land base and feed produced, and a nutrient balance between the manure nutrients applied and imported in purchased feed, and the nutrients used for crop production, exported milk and meat, or otherwise exported from the farm. 3.1.1. Type of dairy farm The most common housing system on dairies in the Great Lakes Region is the total confinement system, which typically has cattle inside a free stall barn all year round consuming rations that are relatively high in concentrates and harvested forages. Large, confined herds require large structures for housing and feed storage, and material handling equipment and waste management systems (USDA-NRCS, 2007). Confinement dairies have more control of feed 52 quantity and nutrient concentration during the year, which influences milk production and the quantity and nutrient concentration in manure (Wattiaux and Karg, 2004). In an annual pasture-based system cattle are on pasture or open lots throughout the year consuming grazed forage during the growing season and stored feed throughout the winter. Pasture-based dairies can reduce feed, labor, equipment, and fuel costs. They provide a lowercost option for small farms without the need to expand herd size (USDA-NRCS, 2007). Mechanical feed harvesting and storage are greatly reduced because the cows harvest the crop directly from the field much of the year. Seasonal pasturing has been adopted largely due to the profitability of the dairy industry in the Great Lakes Region (Nott, 2003). Less purchased feed is required; therefore, fewer hectares need to be harvested as stored forage. Some producers use seasonal grazing which is a combination of the two systems and is attractive because it reduces costs by allowing the feeding of concentrate to improve milk production levels. 3.1.2. Cattle frame Ninety percent of U.S dairy cows are black and white Holsteins. Holsteins can produce large volumes of milk, butterfat and protein. When fed high levels of grain the cow can be very profitable (EPA, 2012a). Cattle frame varies depending on the type of dairy system. Large-frame Holsteins are typical in conventional confinement systems with a mature body weight of 726 kg (1,600 lb), bred for high milk production. Cattle in seasonal pasture systems are typically medium-framed cattle (590 kg mature weight) with traits and genetic potential for milk production between the large-frame and small-frame cows. Managers of annual pasture-based systems prefer small-framed New Zealand Friesian cattle (454 kg mature weight) because of their efficient conversion of grass to milk. 53 3.1.3. Land base A land base of 111 ha (275 ac) was selected for each of the dairy systems evaluated (confinement, seasonal pasture and annual pasture) while varying areas for grazing, corn and alfalfa production. This land base maintained a near balance of feed produced on farm with small amount of purchased or sold forage or grain, and nutrient balance on the farm with manure application. The key farm parameters when matching cow numbers with the available land base were: Feed production and utilization: indicates how much feed is produced, sold or purchased. The target was to match feed production with use, with only small amounts of forage and grain purchased or sold. Nutrient balance: used to maintain soil fertility with small amount of soil phosphorus and potassium build-up or depletion. 3.1.4. Milk production Milk production is a function of genotype, management level, nutrition and environmental factors. Large-frame Holsteins in confinement typically have greater annual milk production than small-frame cattle on pasture. The confinement system with 100 large-frame Holsteins had a target annual (305 days) milk production without fat in the ration of 10,886 kg/cow-yr (24,000 lb/cow-yr). The seasonal pasture system with 142 medium-frame Holstein cows had a target milk production of 9,071 kg/cow-yr (20,000 lb/cow-yr). The annual pasturebased system had a target milk production of 7,252 kg/cow-yr (16,000 lb/cow-yr). Potential milk fat content was 3.5% for the large-frame cows, 3.8% for the medium frame cows and 4.2% for the small-frame cows (Utsumi, personal communication, 2013). At these production levels forage quality was the primary constraint to milk production. 54 3.1.5. Type of Manure Treatment Two types of manure treatment were evaluated: land application of raw manure and anaerobic digestion. Land application of raw manure means that all manure collected on-farm was applied to the crop land. When an anaerobic digester was used all the manure collected or imported was used as biomass for the digester and the digestate from the digester was applied to crop land. Five representative farms scenarios were evaluated: 1) conventional confinement system with 100 large-frame Holstein, 2) conventional confinement system with 100 large-frame Holstein and AD, 3) seasonal pasture system with 142 medium-frame Holstein, 4) seasonal pasture system with 142 medium-frame Holstein, imported manure, cash crop and AD and, 5) annual pasture-based system with 160 small-frame New Zealand Friesian. The different farms were compared by observing the outputs of farm performance, costs, gas emissions and footprints (Appendix D). A calculation of the difference between means of each farm was compared. IFSM is not currently designed to evaluate an anaerobic digester with imported manure. Therefore the performance, economics and environmental impact of the seasonal pasture dairy was approximated by comparing multiple representative farms, one with an anaerobic digester and a seasonal pasture dairy with imported manure and an expanded land base for cash crop production and manure use. Because the manure production from a 500-cow dairy is generally considered to be the threshold for a breakeven investment in an anaerobic digester a 500-cow confinement dairy with an anaerobic digester was evaluated and found to produce 15,600 t (17,200 ton) per year of manure. The AD installed on the seasonal dairy was sized to process this volume of manure (15,600 t) with 2,885 wet t produced by the cattle at the dairy and 12,882 wet 55 t of manure imported from nearby farms. In addition, to evaluate the environmental impact of an anaerobic digester in the seasonal farm an AD sized to process the amount of manure produced by 142-cows (2,885 t) was evaluated. In order to evaluate the integration of a seasonal pasture farm with an anaerobic digester the differences and percentages obtained between the confinement farm with 500 cows with and without AD and, between the seasonal farm with 142 cows with and without AD were used (Table 10 and Table D.1). Information that is not included in Table 10 is the same as the seasonal dairy farm with 142 medium-frame Holsteins with additional land for cash crop and imported manure. Because IFSM does not account for the separate labor and machinery requirements for imported manure in the seasonal farm with AD, the costs related to importing the additional manure and the land application of it were calculated, and these costs were added to the farm production costs (Table C.19). Due to the imported manure the seasonal farm crop land was increased from 111 ha to 809 ha to achieve a near nutrient balance. Corn acreage was increased from 75 ha to 374 ha and 374 ha of soybeans were added as a cash crop (Figure 5). Additional description of farm input parameters are included in Appendix C. Farm performance, economics and environmental impacts due to the integration of an AD into a seasonal pasture farm were evaluated by comparing the seasonal dairy farm and the seasonal dairy farm with AD, imported manure and additional land for cash crop. The final analysis included the farm performance and economic and environmental impacts due to the transition from confinement systems to an annual pasture-based system and the integration of anaerobic digester in a confinement and seasonal pasture system. 56 Farm performance included economics and resource use, annual production costs and net return to management; crop production costs and total feed costs. Environmental impacts included nutrients available on farm, used, and lost to the environment; annual emissions of important gaseous compounds; and environmental footprints of water, nitrogen, energy and carbon. 57 Data collected from site visits and literature review for representative farms Confinement -Large Holstein -100 cows -Cows confined year round Assumption Type and size of cows typically used for confinement systems in the Great Lakes Region Confinement with Anaerobic Digester -Large Holstein -100 cows -Cows confined year round Assumption -Manure volume was not economically viable for AD Seasonal Pasture -Medium Holstein -142 cows -Cows confined during winter and pastured during summer Assumption Type and size of cows typically used in seasonal pasture system Figure 5. Development of five representative dairy production systems 58 Seasonal Pasture with Anaerobic Digester -Medium Holstein -142 cows -Cash crop land -Imported manure Assumption -Imported manure to evaluate AD economics and performance -Increased crop land to maintain nutrient balance Annual Pasture -Small New Zealand Friesian -160 cows -Cows on pasture all year round Assumption Type and size of cows typically used for pasturebased systems in the Great Lakes Table 10. Estimated values for the seasonal pasture dairy with 142 medium-frame Holsteins, anaerobic digestion, imported manure and additional land for cash crop production. Equations used Nutrients available, used, and lost to the environment [a] [d] [b] [c] [a] Nitrogen lost by leaching Seasonal 142 w CC w Import + (Seasonal 142 w CC w Import * (% Dif. Seasonal 500 AD-Seasonal 500)) Nitrogen lost by denitrification Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 500 ADSeasonal 500)) Potassium loss through runoff Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 500 ADSeasonal 500)) Soil potassium depletion Seasonal 140 w CC w Import Crop removal over that Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADavailable on farm Seasonal 140)) Annual manure production and handling cost Manure handled Confine 500 AD Manure applied to corn land Confine 500 AD Machinery cost Seasonal 140 w CC w Import + (Dif. Confine 500 AD-Confine 500) Fuel and electric cost Seasonal 140 w CC w Import + (Dif. Confine 500 AD-Confine 500) Storage cost Seasonal 140 + (Dif. Confine 500 AD-Confine 500) Labor cost Seasonal 140 w CC w Import + (Dif. Confine 500 AD-Confine 500) Annual crop production and feeding costs and the net return over those costs Equipment cost Machinery cost of manure+ Equipment cost of crop-custom cost (Seasonal 140 w CC w Import w AD) Facilities cost Seasonal 140 w CC w Import + (Dif. Confine 500 AD-Confine 500) Energy cost [(Total energy (Mbtu) - Energy Animal housing ventilation and lighting (Mbtu) ) + Excess electricity (Mbtu)] * 0.028 ($/Mbtu) Land rental cost Seasonal 140 w CC w Import + (Dif. Confine 500 AD-Confine 500) Return to management and Costs-Incomes 59 Table 10 (cont’d) unpaid factors Annual emissions of important gaseous compounds Ammonia Housing facility Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Manure storage Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Methane Manure storage Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Biogenic Carbon Dioxide Manure storage Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Combustion Carbon Dioxide Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Environmental footprints of water, nitrogen, energy and carbon for a dairy farm Water Use Production of purchased feed Seasonal 140 w CC w Import and inputs Not allocated to milk Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADproduction Seasonal 140)) Water footprint with rainfall Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Water footprint without rainfall Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Reactive Nitrogen Loss Ammonia emission Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) 60 Table 10 (cont’d) Nitrate leaching Nitrous oxide emission Fuel combustion emissions Reactive nitrogen footprint Energy Use Manure handling Production of resource inputs Not allocated to milk production Energy footprint Greenhouse Gas Emissions (CO2e) Manure emissions Emission during feed production Net biogenic carbon dioxide emission Fuel combustion emissions Production of resource inputs Not allocated to milk Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 500 ADSeasonal 500)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Cost for manure handling/ 0.028 (Seasonal 140 w CC w Import /AD) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) (Sum Energy Seasonal 140 w CC w Import w AD)/ (lb FPCM Seasonal 140 w CC w Import ) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 AD61 Table 10 (cont’d) production Carbon footprint without biogenic CO2 Carbon footprint w/ biogenic CO2 Seasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) Seasonal 140 w CC w Import + (Seasonal 140 w CC w Import * (% Dif. Seasonal 140 ADSeasonal 140)) [a] 140/500 = number of cows; [b] CC= cash crop; [c] Dif.= difference; [d] w = with 62 3.2. Herd and crop information of representative farms The dairy herds included large and medium-frame Holstein cows, small-frame New Zealand Friesians cows and replacement stock. Dry cows formed 15% of the milking herd. The land base was selected to provide all forage and grain to a herd of 100 large-frame Holsteins with only a small amount of forage or grain purchased and sold on an annual basis to balance the feed produced on the farm. The number of cows in the milking herd was increased to provide a near nutrient balance on crop removal, available feed and manure produced by the dairy herd (Table 11). The mature cow body weight was 726 kg (1,600 lb) for the large-framed cows and, 590 kg (1,300 lb) and 454 kg (1,000 lb) for the medium and small-framed Holsteins, respectively. Potential annual (305 day) milk production without fat in the ration was 10,886 kg/cow (24,000 lb/cow) for the large-frame Holsteins, 9,071 kg/cow (20,000 lb/cow) for the medium-frame Holsteins and 7,257 kg/cow (16,000 lb/cow) for the small-frame New Zealand Friesian. At these milk production levels forage quality was the primary constraint. Potential milk fat content was 3.5% for the large-frame cows, 3.8% for the medium frame cows and 4.2% for the small-frame cows (Utsumi, personal communication, 2013). The herds followed a year-around calving strategy with a 35% culling rate for the confinement system, 25% for the seasonal pasture system and 30% for the annual pasture system as a result of healthier lactating cows, with less stress, more natural diet and, improved reproductive performance (Utsumi, personal comunication based on Benbrook, et al., 2010). Labor for milking and animal handling was 5.25 min per cowday for the confinement system, based on three times per day milking schedule and, 3.0 min per cow-day for the seasonal and annual pasture systems, assuming 2 times milking per day and lower milk production (Utsumi, personal communication, 2013) (Appendix Table C.5). 63 Table 11.Major descriptive parameters of five representative dairy production systems Unit Confine Confine Seasonal Seasonal w/ AD Pasture Pasture [a] w/ AD Livestock Lactating cows 85 85 121 121 Dry cows 15 15 21 21 Young stock over one 38 38 54 54 year Young stock under one 42 42 60 60 year Alfalfa Land area ha (ac) 36.4 36.4 10.1 10.1 (90) (90) (25) (25) Harvest system Hay and Hay and Hay and Hay and silage silage silage silage Number of cuttings 4 4 4 4 [b] Avg. yield 11.78 11.78 11.62 11.61 t DM /ha (5.26) (5.26) (5.19) (5.18) (ton DM/ac) Corn Land area for confinement Harvest system Number of cuttings Avg. dry corn yield Avg. high moisture yield Avg. silage yield Grass Land area ha (ac) Annual Pasture 136 24 61 67 40.5 (100) Hay and silage 4 11.64 (5.20) 74.8 (185) Grain, silage 1 6.41 (2.86) 6.09 (2.72) 12.64 (5.64) 50.6 (125) Grain, silage 1 5.98 (2.67) - 374 (925) Grain, silage 1 6.18 (2.76) - 0 t DM/ha (ton DM/ac) t DM/ha (ton DM/ac) t DM/ha (ton DM/ac) 74.8 (185) Grain, silage 1 6.45 (2.88) 6.11 (2.73) 12.74 (5.69) 12.92 (5.77) 13.79 (6.15) - ha (ac) 0 0 50.6 (125) Silage 1 3.78 (1.69) 50.6 (125) Silage 1 4.12 (1.84) 70.8 (175) Silage 1 3.83 (1.71) - Harvest system Number of cuttings Avg. yield t DM/ha (ton DM/ac) [a] Seasonal Pasture with AD, cash crop and imported manure [b] t = metric ton; DM=Dry matter - The feed ration was determined by a linear program embedded in IFSM and it was selected to provide a relatively high forage-to-grain ratio and a minimum of 5% dry hay in cow 64 rations was fed for all farms. The phosphorous and protein were fed at 100% of National Research Council (NRC) recommendations. Corn grain, corn silage, dry hay, pasture, grass and alfalfa chopped and baled silage was produced on the farm. A soybean meal crude protein supplement, distiller grain and minerals were imported to the farm. A loader and mixer wagon were used for feeding grain and silage. A bale grinder was used for feeding hay (Appendix Table C.6). The animal facilities for confinement and seasonal pasture included a double six parlor milking center, free stall barn naturally ventilated as cow housing, calf hutches and a dry lot as heifer housing, and short-term storage of premix feed (Appendix Table C.7). Bedding was chopped straw providing 1.4 kilograms per cow- day (3 lb/cow-day). The purchased bedding for the farms with an anaerobic digester was reduced to 0.45 kg per cow-day (1 lb/cow-day) because 0.95 kg/d was recycled from the solid part of the digestate (Appendix Table C.8). The annual pasture-based system included a double-six parlor milking center, calf hutches and a dry lot as heifer housing with short-term storage for premix feed. No bedding was provided. Corn and alfalfa were grown on each farm other than the annual pasture-based farm where only alfalfa and grass/legume pasture were grown. The pasture was 70% cool-season grass and 30% legume mix pasture on the pasture-based farms. The soil was a medium sandy loam with total water holding capacity of 19 cm (7.5 in), and soil phosphorus at an optimum level between of 30 to 50 ppm. Alfalfa had a stand life of 4 years, and grass 10 years. The relative maturity index of corn was 100 days, with a plant population of 69,189 plants per hectare (28,000 plants/ac). The P and K balance was achieved with the manure application with a small, long-term build-up or draw-down. Twenty-eight kilograms per hectare (25 lb/ac) of nitrogen was applied to the corn at planting time. All manure was applied to land going to corn production. 65 Nitrogen from legumes and manure applied by the grazing animals supplied the nutrients for the grass pasture. In the annual pasture-based system 80% of manure collected from the milking center was applied to grass and 20% to alfalfa (Appendix Table C.3). The confinement, seasonal pasture and annual pasture-based systems had 111 ha available for crop production. The confinement farm had 36 ha of land in alfalfa and 75 ha for corn production. The annual pasture-based farm had 40 ha for alfalfa and 79 ha as grazing area. The seasonal pasture farm had 10 ha for alfalfa, and 51 for corn and 51 ha as grazing area. The seasonal pasture with additional cash crops and an AD system had additional crop land to maintain the nutrient balance with the imported manure. The total land area of the seasonal pasture with cash crop and AD was 809 ha: 374 ha in corn, 374 ha in soybeans, 10 ha in alfalfa, and 51 ha in pasture (Table 11). Manure was collected, stored and applied as a semi-solid (12-14% DM), which represents fresh manure plus bedding. Total manure dry matter was the sum of manure excreted by the cows plus bedding and feed lost into the manure. Manure characteristics were based ASABE D384.2 standard (ASABE, 2013a) (Appendix Table C.8). In the confinement and seasonal pasture-based systems manure was collected with a scraper, stored in a top-loaded, clay-lined earthen basin and loaded in a slurry spreader tank with a slurry pump. The quantity of manure handled was dependent on the amount and type of bedding used and the amount of water contained in the manure. Six months manure storage capacity was provided on the farms with confinement housing, meaning storage was emptied twice each year in the spring and fall (Table 12). Manure on the annual pasture farm was collected from the milking center with scraper bucket loading and short-term storage with a few days capacity (daily haul). 66 Manure was imported to the seasonal pasture farm when an AD was used. 12,882 t/yr of manure was imported and applied to crop land along with 2,885 t/yr produced on the farm. Additional rented land (809 ha) was used to maintain the whole-farm nutrient balance. IFSM does not account for the separate labor and machinery requirements for imported manure (12,882 t/yr). When manure was imported to the farm, additional costs were calculated and added to the farm ownership and operating costs. Agitation, pumping and trucking manure from nearby farms to the AD was done on a custom hire basis at $90 per hour assuming custom hauling with a 22,712 L (6,000 gallons) truck-mounted tank and a 1.6 km hauling distance with a hauling rate of 52,769 L/h (13,940 gal/h) for 15,812 t of wet manure per year. Custom manure hauling required 301 hours per year. Machine efficiency and labor hours were calculated based on Harrigan (2010). Hauling manure from the AD to the field required two 18,927 L (5,000 gallons) tank spreaders with 100 kW tractors with an average hauling distance of 1.2 km. The average hauling rate was 53,942 L/h (14,250 gal/h) and required 148 hours for each tractor and spreader (296 h) based on Harrigan (2010). Labor for pumping and agitating manure required 42 machine hours for agitating and pumping, and 8 hours for agitating and clean-up each time the manure storage was emptied (assumed two times per year) (Appendix Table C.19). Machine efficiency and labor hours were also calculated based on Harrigan (2010). Repair factors, operating costs, salvage value and interest rates were calculated based on Hadrich et al. (2010), ASABE standard D497.7 (2013c) and ASABE standard EP496.3 (2013b) (Appendix Table C.19). 3.3. Tillage and planting information Tillage and planting operations only occurred on days when soil and weather conditions were appropriate for field work. A suitable day was when the soil moisture conditions were 67 suitable to support field operations. Depending on the size and type of equipment specified for each field operation (Table 12), fuel use and labor requirements were determined. A detailed description can be found in Rotz et al. (2011a). Tillage and planting operations primarily occurred in the spring and/or fall. For spring operations, suitable days were determined considering a bare soil (without crop). For summer and fall operations, suitable days were determined using the soil under or following the growing crop using the soil moisture after crop production. Spring operations began with manure application and proceeded through the designated sequence of tillage operations ending with planting. The number of operations that could occur simultaneously was two, and the maximum time that tillage and planting operations could be performed during any given suitable day was 8 hours. Fall operations were similar to spring operations beginning with manure application or after some of the crops were harvested. Tillage and planting operations began with alfalfa and continue with grass and corn. At the end of each simulated year, machine, energy, and labor were summed. The sequence of operations of tillage and planting for alfalfa, corn and grass and the machinery are shown on Table 12. The alfalfa tillage start date was on October 15 using a chisel plow, followed by a field cultivation beginning April 10 and seeding on April 15. Tillage of corn ground began on September 10 with spring seed bed tillage beginning on April 10 and corn planting on May 1, corn operations ended on May 10 with a sprayer. Spring tillage for grass seeding began on April 15 with field cultivation followed by grass seeding on April 20. Soybean tillage began on April 10 with field cultivation followed by soybean planting on May 1 and ended on May 10 with a sprayer (Appendix Table C.14). 68 Table 12. Major machines and structures used for planting and manure storage for five representative dairy production systems Machinery or storage type Farm Size Number Price Tractors and loaders Transport tractors All farms 35 kW (47 hp) 2-5 $12,000 Round bale loader Confinement 50 kW (67hp) 1 $35,100 Annual pasture 65 kW (87 hp) 1 $54,000 Seasonal 80 kW (108hp) 1 $73,350 Skid-steer loader Annual pasture 15 kW (20hp) 1 $30,600 Confinement and 24 kW (33 hp) 1 $39,600 seasonal Tillage and planting Chisel plow All farms 3.7 m (12 ft) 1 $17,100 Seedbed conditioner Confinement and 5.8 m (19 ft) 1 $37,800 seasonal Annual pasture 4.6 m (15 ft) 1 $30,600 Corn planter Confinement and 8 row 1 $31,500 seasonal Grain drill Confinement and 3.7 m (12 ft) 1 $9,900 seasonal 2.4 m (8 ft) Annual pasture 1 $6,750 Sprayer Confinement and 15.2 m (50 ft) 1 $9,900 seasonal Manure handling and storage Slurry tank spreader Confinement and 18 t (20 ton) 1 $39,600 seasonal Small V-tank spreader Annual pasture 6.0 t (6.6 ton) 1 $24,300 Clay lined storage pit Confine 1,707 t (1,882 ton) 1 $45,224 Seasonal pasture 1,541 t (1,699 ton) 1 $44,322 Annual pasture 3 day storage slab 1 0 and back wall Grain harvest and grain crop planting were custom hired, performing the same daily operations using the determined equipment and operations. Machinery, energy, and labor use were not considered part of the farm expenses or energy use. The land area tilled and planted for 69 each crop under custom operation was totaled and multiplied by the custom rate to obtain the total cost. In the annual pasture-based farm forage crop tillage and planting was considered a custom operation. Alfalfa and corn harvest procedures were similar for all farms (Appendix Table C.15 to C.18). Grain harvest was custom-hired for the confinement and pasture-based systems. Corn silage harvest started on September 1 at a maximum silage moisture content of 68% (wet basis). High moisture corn harvest started October 1 and dry corn was harvest started on October 21. Alfalfa was harvest in a four cutting system with the first two cuttings beginning at bud stage on May 25 and July 1 and cuttings three and four at early flower in mid-August and mid-October. Alfalfa was mechanically conditioned and raked before harvest. The critical NDF for high quality storage was 42% for all harvests. Alfalfa was stored as wilted, chopped silage with a maximum moisture content of 60% on the confinement farms and as round bale silage on the farms with cattle on pasture from May 25 to October 15. The maximum moisture content for round bale silage was 68%. Grass for stored silage was harvested at the early head stage with a maximum moisture content of 60% beginning May 20 when the forage supply exceeded forage demand. Corn and alfalfa silage were chopped and stored in bunk silos on the confinement farms and baled and bagged on the pasture-based farms. Dry hay was baled in round bales and stored inside a shed. Farms using confinement stored high moisture grain in an upright silo. A large, portable mixer was used for feed mixing (Table 13) (Appendix Table C.9). The harvested feed was transported on round bale wagons for hay, dump wagons for alfalfa and grain crop silage, and grain wagons for grain. All the feed was transported an average 70 of one-half mile for the confinement, seasonal pasture and annual pasture-based systems and 0.75 mile for the seasonal pasture with cash crop system (Appendix Table C.12 and C.13). Table 13.Major machines and structures used for crop harvest and storage on the five representative dairy production systems Machine or Confinement Seasonal and Annual pasture storage type Size Number Price Size Number Price [a] Mower 4.3 m (14 ft) 1 $26,460 2.7 m (9 ft) $18,900 1(S) conditioner 3.0 m (10 ft) [b] $20,700 1 (A) Tandem rake 5.5 m (18 ft) 1 $19,350 5.5 m (18 ft) 1(A) $19,350 Single rake 2.7 m (9 ft) 1(S) $6,300 Round baler Small 1 $20,340 Medium 1 $30,240 Bale wrapping Large 1 $9,720 Forage Medium 1 $32,400 Medium 1(S) $32,400 harvester Corn combine 8 row 1 $267,300 8 row 1(S) $267,300 Feed mixer 12 t (13 ton) 1 $63,900 12 t (13 ton) 1 $63,900 Forage blower 1 $40,050 1(S) $40,050 Forage wagons 3.6 t (4 ton) $6,000 $6,000 Hay storage 109 t (120 ton) 1 $25,960 109 t (120 ton) 1 $25,960 shed Alfalfa bunker 384 t (423 ton) 1 $56,982 82 t (202 ton) 1(S) $32.567 silo 384 t (423 ton) 1(A) $56,982 Corn silage 432 t (476 ton) 1 $61,637 432 t (476 ton) 1(S) $61,637 bunker silo High moisture 173 t (191 ton) 1 $38,910 corn stave silo [a] S = seasonal pasture [b] A = annual pasture-based 3.4. Economic information The economic analysis included costs of all major operations on typical farms. The costs were related to resources grown on and brought onto the farm while income was received for milk and feed leaving the farm. All monetary returns from milk, feed, and animal sales occurred in the same year as well as the costs for producing those products. This annual accounting 71 provided a measure of system performance that reflected one year’s use of resources to produce that year’s production (Rotz et al, 2011a). The economic information was based on ownership costs determined by amortizing the initial investment over the life of the system. General economic parameters specify the prices of energy inputs, the economic life and salvage values of machines and structures, labor wage, land rental, and the real interest rate (Table 15). Cropping cost parameters include the cost of fertilizer, seed, and chemicals for producing each crop. Commodity price parameters include the buying prices of feeds and the selling prices for milk, animals and excess feed. Custom operation parameters describe the costs associated with hiring a custom operator to carry out specific farm operations. In this case the hired custom operations were for corn grain harvest and planting, forage crop tillage and planting and transport of manure from off farm to the AD. The budgeting process included fixed and variable costs of production. Annual fixed costs for equipment and structures were a function of their initial cost and economic life which was 10 years for machinery and 20 years for structures (IRS publication 94b) and a real interest rate of 6%. Annual fixed costs were summed with annual expenses to obtain a total production cost. This total cost was subtracted from the total income received for milk, animal, and excess feed sales to determine a net return to the herd and management (Rotz et al., 2011a). Table 14 presents the major dairy costs and Table 15 presents economic parameters used in all farms, which were obtained between the years 2011 and 2013 from USDA-NASS, USDA-NRCS, U.S Energy, Michigan Public Service, Michigan adverse effect wage rate (AEWR), Michigan State University Extension, Purdue University Extension and Iowa State University (Appendix Table B.9). 72 Table 14. Major dairy costs ($/cow-year) Confine Seasonal pasture $1,400 Heifer housing [c] Milking center [d] Feed facility $264 $267 $2,197 $1,950 $45 [b] $1,380 $3,120 Cow housing Annual pasture 0 $267 [a] $44 $45 [e] $418 $551 $359 Total $5,383 $4,244 $2,680 [a] Free stall barn, naturally ventilated [b] Calf hutches and dry lot [c] Double six parlor [d] Short term storage of premix [e] Includes veterinary and medication, semen and breeding, animal and milking supplies, insurance of animals, utilities for milking and animal handling, animal hauling and DHIA, registration. Livestock expenses Table 15. Economic parameters and prices assumed for five representative dairy production systems Parameter Value General rates Diesel fuel $0.98/L ($3.698/gal) Electricity $0.13/KWh Grain drying $ 1.76/pt-t ($1.6/pt-ton DM) Labor wage $16.13/h Land rental $126/ha ($50.98/acre) Property tax 2.5% Fertilizer prices N $1.19/kg ($0.54/lb) P $1.63/kg ($0.74/lb) K $1.26/kg ($0.57/lb) Lime $33/t ($30/ton) Annual seed and chemicals New forage stand $494/ha ($200/acre) Established forage stand $17.3/ha ($7/acre) Corn land $551/ha ($223/acre) Additional for corn following corn $12.4/ha ($5/acre) rotation Selling prices Grain crop silage $110/t DM ($100/ton DM) 73 Table 15 (cont’d) High moisture grain Corn grain High quality hay Milk Cull cow Bred heifer Buying prices Soybean meal 48% Distillers grain Corn grain Hay Minerals / vitamins Bedding material Custom operations Grain harvest Grain crop planting Forage crop tillage/planting Economic life Machinery Structures Machinery salvage value Real Interest rate $243/t DM ($220/ton DM) $298/t DM ($270/ton DM) $14/t DM ($13/ton DM) $0.42/kg ($19/cwt) $1.88/kg ($85.5/cwt) $300/ animal $402/ t DM ($365/ ton DM) $165/t DM ($150/ ton DM) $160/ t DM ($145/ ton DM) $198/t DM ($180/ ton DM) $220/t ($200/ ton) $110/t ($100/ ton) $77.5/ha ($31.4/acre) $40.0/ha ($16.22/acre) $138.3/ha ($56.0/acre) 10 years 20 years 30% 6% 3.5. Pasture growth and management Part of the forage produced (alfalfa or grass-based) can be fed directly to the animals by grazing. The grazing area was varied during the spring, summer and fall to reflect the reduction of land needed when excess forage in the spring exceeded demand, and a small portion of land lost from production in the fall for grassland renovation. Excess forage in the spring was harvested as grass silage and stored in plastic-wrapped bales (Table 16). Spring grazing occurred during the months of April, May, and June; summer grazing in July and August; fall grazing in September and October. Detailed information about pasture management can be found in Rotz et al. (2011a). 74 The model provided yield and nutritive content of pastures for the grazed land based on the GRASIM model. GRASIM predicts pasture production and plant growth for hay and silage production. For a grass-based pasture, production was simulated in thirty-day intervals between harvests and makes 60% of the forage for the grazing animals available. The remaining 40% was considered the initial condition for regrowth. The required information was investment in fence and watering equipment, and the labor needed to manage this equipment and the grazing animals. This information was used to determine the production costs related to pasture. Fence was divided in perimeter and temporary fence. Perimeter fence was a permanent fence such as high tensile wire. Temporary fence was movable polywire. Also included in the fencing system are gates and lanes for moving animals (Table 16) (Appendix Table C.4). The labor required for pasture management included the time for evaluating pasture and the animals on that pasture, labor for moving temporary fence and watering equipment, and the labor required for retrieving animals for milking or moving them to new paddocks (Table 16). Most of the pasture area was assumed to be clipped once per year. The pasture area clipped each year was set to the area defined as the summer grazing area. The clipping rate and fuel consumptions are functions of the size and type of mower used and the tractor used to power the mower. The grazing strategy was based on the animal groups placed on pasture and the amount of time they spent on the pasture. The groups of animals that were on pasture were: older heifers, dry cows and, lactating cows (Table 16). The time animals spent on pasture was set as full days during the grazing season (from April through October), which means between 16 and 18 hours per day (Table 16) for the 75 seasonal pasture farm. The pasture-based farm was set as full days all year, which means between 18 and 20 hours per day. The animals were maintained outdoors year around even though pasture growth may not be available during some months. When not on pasture, animals were housed in the selected facility. Table 16. Grazing parameters for the seasonal and annual pasture systems Unit Seasonal Grazing area Spring ha (ac) 30.4 (75) Summer ha (ac) 50.6 (125) Fall ha (ac) 40.5 (100) Grazing management costs Investment in perimeter fence $ 3,625 Investment in temporary fence $ 2,125 Investment in watering system $ 3,125 Added annual cost of seed and chemical $/ha ($/ac) 74 (30) Grazing strategy Labor for grazing management h/ week 10 Types of animals grazed All cows Time on pasture h Full days during grazing Annual 40.5 (100) 70.8 (175) 60.7(150) 5,075 2,975 4,375 74 (30) 10 All cows Full days during grazing Pasture was allocated along with other available feeds to meet the nutrient needs of each animal group in the herd. This was done using a partial mixed ration that best complimented the quantity and nutrient content of the pasture consumed. The pasture consumed was limited by either what available or the maximum amount of pasture forage that was consumed, which was the maximum amount of forage that could be included in the animal diet along with the available supplemental feeds required to maintain the desired production level. Diets of each animal group were formulated with a linear program set to maximize forage use in the ration. If there was some excess of pasture forage available on the farm, all the animal groups that were being grazed could consume that forage in the ration. When forage was 76 supplemented to meet herd needs, pasture was allocated first to grazing heifers and dry cows. Any remaining pasture was combined with available hay and silage or purchased hay to meet the roughage needs of the lactating cows. If during one month the pasture ran out before all animals were fed or during the months pasture was not available, animals were fed using hay and silage. The nutritive content of pasture varied throughout the grazing season. Crude protein was set at 26% in the spring, dropped to 23% in the summer, and rebounded to 26% in the fall. Net energy for lactation started at 1.57 Mcal/kg DM in the spring and slowly decreased to 1.42 Mcal/kg DM in the fall. Neutral detergent fiber started at 52% in the spring, increased to 55% in the summer, and dropped to 53% in the fall. The rumen degradability of protein was set at 80% of CP, and the ADIP content was set at 2% of DM. Phosphorus and K contents were a function of the predominant crop. For grass-based pasture, the assigned P and K contents were 0.35% and 3%, respectively. For alfalfa, the P content was 0.26%, and the K content was 2.5% of DM (Rotz et al., 2011a). 3.6. Crop nutrient requirements, nutrient availability and loss An embedded soil model was used to predict moisture and nitrogen available for the growth and development of each crop. Moisture content was predicted by tracing precipitation based on 26 years of local weather data, runoff, evapotranspiration, moisture migration, and drainage through time. Nitrate Leaching and Economic Analysis Package (NLEAP) was the model used to predict nitrogen cycling in the soil. Each soil layer includes nitrate, ammonia, crop residue nitrogen, manure organic nitrogen, and other soil organic matter. Nitrogen uptake by the crop was limited by availability or demand of the crop. Additional information about crop nutrient requirements can be found in Rotz et al. (2011a). 77 Daily nitrogen losses from the soil due to volatilization, leaching, and denitrification were also predicted by the model. Volatilization was a function of the amount of ammonia, temperature, and a volatilization rate. Leaching loss was related to the amount of nitrate and moisture that drained from the lower layer. Denitrification was a function of denitrification rate, temperature, and the water-filled pore space in the soil. The fertilizer application rates included: nitrogen, phosphorous and potassium, and the percentage of manure applied. The manure application rate was determined by the manure application divided by the crop land area. Manure nutrients were calculated as dry matter of manure times the concentration of each nutrient in the dry matter manure. Nitrogen concentrations of manure were determined after subtracting the losses during collection, storage, and application. The nutrient accumulation in the soil and the loss to the environment were predicted by the whole-farm mass balance. The whole-farm mass balance of nitrogen, phosphorus, potassium, and carbon was determined as the sum of all nutrient imports in feed, fertilizer, manure deposition and legume fixation minus the exports in milk, excess feed, animals, manure, and losses leaving the farm. The amount of manure applied to each crop was the percentage of the total manure applied to that crop times the total amount of manure handled annually. The percentage of manure deposited during grazing was not included in the total manure handled. The amount of manure applied during grazing was determined by the animal groups and the time they spend on pasture. For this study the animals were set to be year around on pasture for the annual pasturebased system and summer grazing for the seasonal pasture system, meaning that about 85% of the total manure produced was deposited during grazing. 78 3.8. Anaerobic digestion IFSM predicted the production and use of energy, and the effects that anaerobic digestion has on manure, nitrogen, phosphorous and economics (Figure 6). The AD manure loading rate was the amount of manure excreted and collected from barns or transported to the farm from off farm locations. Biogas is produced through the microbial degradation of the volatile solids in the manure. Energy production was based on the rate of volatile solids (VS) flow into the digester from animals. The amount of methane produced was a function of the productivity, which was set at 0.35 kg CH4/Kg VS (Moller et al, 2007), and a function of the conversion efficiency, which had typical values close to 35% (Burke, 2001; Rotz et al., 2011a). Predicts AD Production and use Biogas Bedding Changes Manure Nitrogen and Phosphorous Electricity Economics Figure 6. Anaerobic Digestion in IFSM Producing power with biogas was a function of the energy content of methane, which also depended on biogas leakage (set as a typical value of 15%) (Kirk, personal communication, 2013). IFSM first predicted the amount used to heat water, which was set as 40% of the gas production, and the remaining was available to generate electricity (Table 17). The amount of 79 electricity produced each day was limited by either the capacity of the generator, operation time and the amount of biogas. The efficiency of the engine-generator was set as 35% (Kirk, personal communication). Any remaining biogas that was not used for either electricity generation or water heating was burned off in a flare. By burning the biogas the lost carbon converted to carbon dioxide, which reduced the global warming potential of methane emission. The initial costs for the anaerobic digester were calculated using a model provided by Safferman (personal communication, 2013) where the cost of the digester was calculated based on $7,000/kW and the generator was assumed to be 50% of the cost of the digester. The digester cost ($7,000/kW) was obtained from a review of like projects around United States and Michigan State. The initial costs of the digester and generator included: digester structure, electrical generator, design, construction, planning and, digestate management. The model do not include modifications required to collect and hold manure prior entering the digester. The costs may be lower because the electric generation equipment, which is smaller than usual, may be difficult to find. The input parameters were: quantity of manure, moisture content, volatile solids, total solids, volatile solids conversion efficiency and run time efficiency (Table 17). The model outputs were: initial cost of digester and generator, repair and maintenance cost, electric generation equipment, gross energy from biomass, net energy from electricity including efficiency, transportation waste energy, energy for heating influent and to operate AD and, heat production from generator. For IFSM only the initial costs of the digester and generator described above, repair and maintenance costs and, electric generation equipment calculated from the model provided by Safferman (personal communication, 2013) were used (Table 17). 80 Table 17. Anaerobic digester parameters Unit CH4 content Heat of combustion Digester wet t/yr (wet ton/yr) wet t/yr (wet ton/yr) % % % % % Seasonal pasture with AD 3,155 (3,478) 2,885 (3,180) 0 12,882 (14,200) 90 90 80 80 10 10 80 80 55 55 kJ/mole methane Manure collected on farm Manure imported to farm Moisture content Volatile solids Total solids VS/TS (% of TS) Confine 890 890 117,000 539,000 2 15 35 2 15 35 [a] $ Initial cost purchase price Repair and maintenance cost % of initial cost Biogas leakage % of gas produced Volatile solids conversion % of initial volatile solids efficiency Generator and other Equipment [a] Generator Capital cost Repair and maintenance cost ( $0.015/ kWh) Annual repair and maintenance Operation labor requirement Electric generation equipment Electric generator efficiency Run time efficiency Biogas used for water heating Total digester, generator and other equipment Energy $ 59,000 270,000 $/ year 1,755 7,920 % of initial equipment cost h/week kW % of energy input % of total time % of gas produced $ 3 20 17 35 85 40 176,000 3 20 77 35 85 40 809,000 Gross energy from biomass MMBtu/yr 1,143 Net Energy from electricity MMBtu/yr 400 including efficiency Transportation waste energy MMBtu/yr 2 Energy for heating influent MMBtu/yr 213 Energy to operate AD MMBtu/yr 57 Heat production from MMBtu/yr 594 generator [b] MMBtu/yr 178 Total net energy [a]Structure economic life is 20 years, and real interest rate is 6%. 81 5,173 1,810 8 963 259 2,690 806 Table 17 (cont’d) [b] Total net energy accounting for all operational needs including transportation, biomass availability, influent heat, digester heat, digester operation, digester operational time, generator efficiency, and generator operational time. The quantity and nutrient content of the manure produced were predicted based on the feeds consumed and the characteristics of the herd. The digestion process reduced the volatile solids content in the effluent, reduced the odor and methane produced compared to untreated manure. The digestion process also affected the nitrogen fractions in the manure. A portion of the + organic N in the raw manure was decomposed to NH3 and NH4 , also referred as TAN (total ammoniacal N). IFSM based the amount of TAN in effluent entering long term storage upon data collected by Gooch et al. (2007), which is modeled as 15% greater than that entering the digester. This increase in TAN potentially increases the ammonia emissions from the storage and field applied effluent (Rotz et al., 2011a). Phosphorous solubility was also increased during the digestion process. The amount of soluble phosphorus entering long term storage in the digester effluent was increased by 13% compared to untreated manure (Gooch et al., 2007). The increased solubility affected phosphorus runoff following field application (Rotz et al., 2011a). Regarding cost, adding an anaerobic digester to the dairy farm increased the ownership and operating costs and reduced purchased electricity and bedding cost. When bedding and electricity was produced on the farm, the cost was reduced in proportion to the reduction in purchased bedding or electricity. 3.9. Environmental impacts In the environmental section of IFSM, the model does not allow adjustment of parameters. The environmental impacts modeled by IFSM included volatile, leaching and denitrification losses of N; volatile loss of hydrogen sulfide; surface runoff and leaching of 82 phosphorous; and greenhouse gas emissions of carbon dioxide, methane, and nitrous oxide. In addition, other sources of emissions such as ammonia and hydrogen sulfide originating from manure on the barn floor, the manure storage and field applied manure were included. More detail about the environmental impacts can be found in Rotz et al. (2011a). Most of the methane emissions were due to enteric fermentation and long term manure storage with minor sources being the barn floor, field applied manure, and feces deposited by grazing animals. Carbon dioxide sources included plant, animal and microbial respiration, both in soil and stored manure. Nitrous oxide is the strongest of all greenhouse gas emissions occurring in agricultural production with a global warming potential 298 times that of CO2 (IPCC, 2007). Nitrous oxide sources included nitrification and denitrification processes in the soil, and these processes also occurred in the crust of slurry manure storage (Rotz et al., 2011a). The phosphorous cycle is a complex process because it has various chemical forms and transformations. These processes are modeled in IFSM using relationships from the ErosionProductivity Impact Calculator (EPIC) and the Soil and Water Assessment Tool (SWAT) to better represent surface processes. Surface processes include surface application, runoff, and transformation along with soil-surface interactions through infiltration and tillage. Erosion sediment loss is predicted using the Modified Universal Soil Loss Equation (MUSLE). Total manure nitrogen consists of organic and ammoniacal nitrogen (NH3-N). During manure handling, ammoniacal nitrogen is transformed and volatilized as ammonia. The primary source of ammoniacal nitrogen is urine, but a portion of the feces can also transform to an ammoniacal form during prolonged storage periods. Between 1% and 10% of TAN was lost when manure was applied through broadcast spreading. When manure was applied to a soil 83 surface, the TAN readily volatilized as ammonia. Therefore, its amount varied through time. During each time step, ammonia loss occurred to the atmosphere and TAN moved into the soil through infiltration. Hydrogen sulfide is mainly created and emitted from decomposing manure under anaerobic conditions. Main sources include the barn floor and long-term manure storage with minor losses following field application. Hydrogen sulfide is one of the contributors of manure odor. It is also a toxic compound when the concentration builds up in a confined space such as enclosed manure storage. Environmental footprints are expressed as the environment impacts per unit of product. In IFSM, four environmental footprints were evaluated: water use, reactive N loss, energy use, and carbon emission. A footprint was determined by summing the estimates for each of the uses (removing that allocated to co-products), and dividing by the amount of milk produced. Functions or factors were used to estimate values for important uses in the production system. This includes the major uses of water, fossil fuel, and the reactive nitrogen and GHG emissions that occur during the manufacture of resources used in the production system. Secondary uses can include the manufacture or production of fuel, electricity, machinery, fertilizer, pesticides, seed, and plastic used on the farm. Other secondary inputs include any feed or replacement animals purchased and imported to the production system. The major water requirement was for the production of feed crops. Other uses include drinking water for animals, water used for animal cooling, cleaning of the parlor, and holding areas on dairy farms. Reactive nitrogen is essential in the growing of crops and feeding of animals. Only nitrogen in this form can be taken up by crops to form the proteins needed by the animal. The 84 increase in reactive nitrogen in our environment is a concern due to its effect on natural ecosystems and contributions to other forms of air and water pollution. Primary losses of reactive nitrogen include ammonia and nitrous oxide emissions to the atmosphere, nitrate leaching to ground water, and the combustion of fuels. The energy footprint is defined as the total energy required to produce feed and milk, except for the solar energy captured by the growing feed crops. This includes all fuel and electricity directly used in the production system as well as the secondary energy used in the production of resources used on the farm. One of the major uses of energy on farms is the fuel used to operate tractors and other equipment for feed production, feeding, and manure handling. Fuel use was converted to energy units assuming 35.8 MJ/L of fuel. Electricity was another major use mainly for milking, ventilation, and lighting. Electrical use was converted to energy units (3.6 MJ/kWh of electricity). Carbon footprint is the total GHG emission expressed in CO2 equivalent units (CO2e). The conversion factor for CH4 and N2O are 25 and 298 CO2e/kg, respectively (IPCC, 2001; EPA, 2007). The carbon footprint was primarily determined as the net emission of the three GHGs including all sources and sinks of CO2. A carbon balance was enforced, so a portion of the CO2 assimilated in the feed was in the carbon exported during feed, milk, and animal productions (Rotz et al., 2011a). 85 CHAPTER 4. RESULTS AND DISCUSSION The IFSM model was used to analyze the transition from a 100-cow conventional confinement dairy to an annual pasture-based system. The analysis included economics and resource use, farm performance and environmental impacts of representative farms. The representative farms included year-around confinement with conventional large-frame Holstein cattle; seasonal pasture with winter confinement and summer pasture with medium-frame Holsteins; an annual pasture-based dairy with New Zealand-style Friesian cattle whereby the cows were on pasture or open lots throughout the year; and the integration of an anaerobic digester on a total confinement dairy and a seasonal pasture dairy with imported manure and an expanded land base for cash crop production and manure application. The representative dairy systems were compared on a fixed land base (111 ha) with largemedium- and small-framed cattle, except the seasonal pasture with AD which had a land base of 809 ha. The base farm for comparison included 100 large-frame cows (85 milking, 15 dry cows) with 80 replacements over 26 years of Lansing, MI weather. Based on the nutrient balance when producing alfalfa, corn silage and corn grain while importing some concentrate and returning the manure nutrients to the land for crop production, the nutrient balance with 100 large-frame cattle with replacements was similar to a seasonal dairy with 142 medium-frame cattle and an annual pasture-based dairy with 160 small-frame cattle plus replacements. 4.1. Comparison of farm performance and resource use The transition from conventional confinement to a pasture-based system affected feed production and the purchase of feed supplements, milk and manure production. Overall, feed consumption increased 23% with the seasonal pasture and 12% with the annual pasture-based 86 system compared to confinement because grazed forage was added to the cattle diet replacing high moisture grain and some alfalfa silage (seasonal pasture) and grain silage (annual pasture). On-farm feed production varied depending on the type of dairy and decreased from confinement to seasonal to annual pasture-based systems. The seasonal pasture produced 15% less milk per cow-yr compared to confinement and the annual pasture-based system produce 31% less per cow-yr. The confinement farms collected more manure than the seasonal and annual pasturebased farms because the cows stayed inside the barn year-around. Additional discussion and detail follows. 4.1.1. Milk, feed and manure production The annual target milk production (305 day) without fat in the ration was 10,886 kg/cow (24,000 lb/cow) for the large-frame Holsteins, 9,071 kg/cow (20,000 lb/cow) for the mediumframe Holsteins and 7,257 kg/cow (16,000 lb/cow) for the small-frame New Zealand Friesians. The annual milk production with the feeds fed was 9,946 kg/cow for the large-frame Holsteins, 8,482 kg/cow for the medium-frame Holsteins and 6,829 kg/cow for the small-frame New Zealand Friesians (Table 18). Because fat was not fed in the diet, forage quality was the limiting factor in milk production. Total annual milk production was 845,430 kg for the large-frame cattle, 1,026,277 kg with the medium-frame cattle and 928,753 kg with the small-frame cattle. 87 Table 18. Average annual milk, feed and manure production of five representative dairy production systems Confine Confine Seasonal Seasonal Annual AD pasture pasture w cash Pasture crop and AD Manure handled t DM/yr 3,155 3,102 2,891 15,329 2,599 Milk production kg/cow-yr 9,946 9,952 8,482 8,479 6,829 Feed and grain production High-quality hay t DM/yr 46 46 16 15 56 Low-quality hay t DM/yr 28 28 5 5 24 Alfalfa/grass silage t DM/yr 233 233 96 101 342 Grain crop silage t DM/yr 374 374 371 375 High moisture grain t DM/yr 151 151 Dry grain t DM/yr 82 79 100 2,889 Total produced t DM/yr 914 911 588 3,385 423 Feed and grain sold Alfalfa Silage t DM/yr 11 13 4 10 25 Hay t DM/yr 14 16 16 Grain silage t DM/yr 15 15 19 41 Cash crop corn and t DM/yr 852 soybeans Dry grain t DM/yr 18 15 37 2,039 Total sold t DM/yr 59 59 60 2,942 41 Feed purchased Hay purchased t DM/yr 13 7 Dry grain t DM/yr 114 Soybean meal 48% t DM/yr 16 17 251 255 204 Distillers grain t DM/yr 121 122 141 148 136 Mineral and vitamin t DM/yr 7 7 6 6 5 Total purchased t DM/yr 144 147 411 416 460 Feed consumed Grazed forage t DM/yr 290 306 281 Hay t DM/yr 60 59 34 27 65 Alfalfa silage t DM/yr 222 220 93 91 317 Grain crop silage t DM/yr 359 359 352 334 High moisture grain t DM/yr 151 151 Dry grain t DM/yr 64 64 63 850 114 Total consumed t DM/yr 999 999 1,229 1,165 1,123 88 The seasonal pasture produced 1,465 kg/cow-yr less milk and the pasture-based system produced 3,117 kg/cow-yr less milk than the confinement dairy. Generally, milk production per cow is lower on pasture-based than confinement systems (Winsten et al, 2000). Reduced milk production in pasture-based systems is usually because of the additional energy the cow expends in harvesting its own forage and the difficulty in balancing cow rations (Muller and Holden, 1994). Typically, the diets of grazing cattle are higher in forages and lower in grain and concentrate. The annual diet in the seasonal pasture system was 24% grazed forage and the annual pasture was 25% grazed forage (Table 18). Feed consumption (including grazed forage) increased by 231 t DM/yr with the seasonal pasture and 124 t DM/yr with the pasture-based system compared to confinement (Table 18). In the seasonal pasture system there was no high moisture corn fed and 129 t DM/yr of alfalfa silage and 26 t DM/yr less hay was fed compared to confinement; however, this was replaced by 290 t DM/yr of grazed forage. In the annual pasture no high moisture corn or grain crop silage was included in the cattle diet but was replaced by 95 t DM/yr of alfalfa silage, 51 t DM/yr of dry grain and 281 t DM/yr of grazed forage. Feed production varied with the cropping system. The confinement and pasture-based dairies produced more high and low quality hay (between 24 and 56 t DM/yr), and more alfalfa and grass silage (between 233 and 342 t DM/yr). The seasonal pasture dairy produced 16 t DM/yr of high quality hay and 5 t DM/yr of low quality hay because only 10 ha were allocated for alfalfa production. The confinement and annual pasture-based systems allocated 36 ha and 40 ha, respectively (Table 18). The pasture-based system did not produce any grain. Grain crop silage production was similar for the confinement and seasonal pasture systems (between 371 and 375 t DM/yr) 89 because the confinement dairy had 75 ha for corn production and the seasonal pasture had 51 ha available. The seasonal pasture with an expanded land for cash crop and AD produced 2,808 t DM/yr of dry grain more than the confinement farm because of the increased crop land in corn (374 ha) and soybean (374 ha) ground. Because of the increased crop land the seasonal pasture with AD produced the greatest quantity of feed sold per year (2,942 t DM/yr) compared to the confinement (59 t/yr), seasonal pasture (60 t/yr) and the annual pasture-based systems (41 t/yr) (Table 18). The confinement dairy purchased 144 t DM/yr of feed compared to 411 t DM/yr for the seasonal pasture and 460 t DM/yr for the annual pasture system. The reduction was primarily soybean meal, 188 and 235 t DM/yr compared to the seasonal pasture and annual pasture-based system, respectively (Table 18). Eighty-six percent of the feed consumed on the confinement dairy was produced on-farm and 14% was purchased. The seasonal pasture system produced 67% of total feed consumed and 33% was purchased. The annual pasture dairy produced 59% of the total feed consumed and purchased 41%. The seasonal pasture with expanded land for cash crop and AD system produced 64% of total feed consumed, 36% was purchased and the remaining crops were sold. The confinement dairy collected more manure (3,155 wet t/yr) than the seasonal pasture (2,891wet t/yr) and annual pasture dairies (2,599 wet t/yr) because the cows were confined in the barn throughout the year. 4.2. Economics The evaluation of farm economics accounted for the major costs related to manure handling and production on-farm and their income from milk and animal sales. Main production costs analyzed on farm were: equipment, facilities, energy, labor, land rental, custom operations, 90 crop production, feed costs and animal expenses. The analysis relates these costs with the type of dairy system (confinement, seasonal pasture or annual pasture-based) and the addition of an anaerobic digester. Overall, the seasonal pasture with imported manure, expanded land base for cash crop production and an integrated anaerobic digester had the highest annual cost for manure handling ($146,985/yr), followed by the confinement dairy with AD ($63,077/yr), seasonal pasture ($36,595/yr), confinement ($35,225/yr) and annual pasture ($15,969/yr), respectively. The seasonal pasture had the highest production cost ($517,738/yr) followed by confinement with AD ($450,238/yr), confinement ($435,960/yr) and annual pasture ($435,894/yr). The seasonal pasture with imported manure, cash crop production and AD had the lowest production cost ($183,481/yr) and the highest net return to management and unpaid factors ($420,192/yr) followed by annual pasture ($88,162/yr), seasonal pasture ($86,133/yr), confinement ($73,594/yr) and, confinement with AD ($62,578/yr). Additional discussion and detail follows. 4.2.1. Manure handling costs Manure was collected, stored and applied as a semi-solid (12-14% DM). In the confinement and seasonal pasture systems manure was collected with a scraper, stored in a toploaded, clay-lined earthen basin with 6-month storage capacity and loaded in a slurry spreader tank with a slurry pump. The bedding was chopped straw supplied at 1.4 kilograms per cow- day (3 lb/cow-day). For the annual pasture system manure was collected only in the milking center with scraper bucket loading and short-term storage with a few days capacity (daily haul). No bedding was added on the pasture-based system. The seasonal pasture with imported manure and an anaerobic digester had the highest cost for manure handling, followed by confinement with anaerobic digestion, seasonal pasture, 91 confinement, and annual pasture. In the confinement and seasonal pasture systems the annual costs for manure handling were: machinery, bedding, labor, storage and fuel and electricity cost (Table 19). The costs for the annual pasture were: machinery, labor and, fuel and electricity costs. There was no storage and bedding cost because manure was hauled daily and no bedding was provided. Table 19. Manure handling costs ($/year) for five representative production systems Seasonal Confine Seasonal Confine pasture w cash AD pasture crop and AD Machinery 16,468 14,097 18,762 25,360 Fuel and electric 1,947 1,677 1,771 6,836 Storage 3,943 24,062 3,864 96,246 Labor 4,561 20,473 4,114 15,848 Bedding 8,306 2,768 8,084 2,695 Total manure handling 35,225 63,077 36,595 146,985 Annual Pasture 8,562 1,790 5,617 15,969 The major costs for confinement with AD were storage ($24,062/yr) and labor ($20,473/yr). Storage cost increased 6 times ($20,119/yr) and labor 4 times ($15,912/yr) compared to confinement without AD. The storage cost increased because of the addition of the anaerobic digester which included design, construction, installation, generator and digester. The total capital cost for the digester, generator and other equipment was $141,000/yr. Labor increased because 20 additional hours per week were required for maintenance of the digester. The seasonal pasture with imported manure and AD followed a different trend than confinement and seasonal pasture. Total manure handling cost increased 4 times ($110,390/yr) compared to the seasonal pasture without AD. Storage cost was $92,382/yr greater than the same farm without an anaerobic digester and imported manure because of the investment in the digester and related equipment (Table 19). Machinery costs for hauling manure increased 92 $6,598/yr, fuel and electric cost increased $5,065/yr and labor increased 4 times ($11,734/yr) compared to the same farm without an anaerobic digester and imported manure. The increase was from hauling the imported manure from the farm where was produced to the anaerobic digester and then hauling and land application of the digestate. 4.2.2. Production costs The seasonal pasture had the highest production cost, followed by confinement with AD, confinement and annual pasture (Table 20). The seasonal pasture with AD had the lowest production cost. Table 20. Total production costs ($/year) for five representative dairy production systems Seasonal Confine Seasonal Annual Confine pasture w cash AD pasture Pasture crop and AD Equipment 98,926 98,090 95,937 92,017 51,273 Facilities 84,452 104,581 85,262 177,623 57,599 Energy 21,871 5,348 20,196 13,293 15,998 Labor 73,943 89,828 64,294 81,912 71,418 Custom operation 3,093 3,078 3,295 97,677 2,380 Seed, fertilizer and 51,111 51,112 38,949 340,373 17,128 chemical Land rental 5,270 5,270 5,270 96,178 5,270 Net purchased feed 21,791 17,414 120,973 (799,143) 120,873 and bedding Animal purchase and 46,600 46,600 50,978 50,978 66,880 livestock expense Milk hauling and 23,730 23,744 27,370 27,359 23,348 marketing fees Property tax 5,173 5,173 5,214 5,214 3,727 Total production costs 435,960 450,238 517,738 183,481 435,894 The major production costs in the confinement and seasonal pasture systems were for equipment, facilities, labor, seed, fertilizer and chemical and animal purchase and livestock expenses (Table 20). The seasonal pasture had higher facilities costs and animal purchase and 93 livestock expenses compared to the confinement system because these costs increased with the number of cows. The confinement system had higher costs for labor, seed, fertilizer and chemicals because it had more crop land for corn and alfalfa production (111 ha) than the seasonal pasture (61 ha) due to the shift in land for grazing animals. The transition from confinement to a seasonal pasture system increased production costs by 18% ($81,778/yr). The transition from confinement to annual pasture decreased production costs by $66/yr (Table 20). The increase in production cost in the seasonal pasture system was because of the increase in purchased feed which was 3.4 times more ($91,515/yr) than the confinement system. The seasonal dairy purchased 235 t DM/yr of soybean meal and 20 t DM/yr of distillers grain more than the confinement system (Table 18) because of the decrease corn production and the change in diet which included 24% of grazed forage. The annual pasture dairy had production costs similar to the confinement system (Table 20). Although housing, machinery, manure handling and other costs decreased on the annual pasture dairy, net purchased feed cost increased ($99,082/yr) with the purchase of 204 t DM/yr more of soybean meal, 136 t DM/yr more distillers grain and 114 t DM/yr of dry grain (Table 18). These energy and protein feeds were needed to approach the target milk production level. Animal purchase and livestock expenses increased by 44% ($20,280/yr) for the annual pasture dairy compared to the confinement dairy because of the increase in cow numbers. Most livestock expenses are related to the number of first lactation animals (Utsumi, personal communication, 2013), therefore high replacement rates are driven by the need to cull cows with recurrent health problems. Grazing cows tend to have fewer serious health problems and improved reproductive performance (Benbrook et al., 2010), therefore, for the annual pasture system 25% were first lactation animals and for the confinement system 35% were first lactation 94 animals. Even though the annual livestock expenses were less ($418/cow-yr) for the annual pasture system compared to the confinement system ($551/cow-yr), total livestock expenses were higher for the annual pasture system because there were more animals on the farm. Compared to confinement, the annual pasture-based system had the greatest reduction in the cost of seed, fertilizer and chemical (66%, $33,983/yr), equipment cost (48%, $47,653/yr), energy cost (27%, $5,873/yr), labor cost (3%, $2,525/yr), property tax (28%, $1,446/yr) and, custom operation (23%, $713/yr) because there was no grain crop production. There was a decrease of 32% ($26,853/yr) in facilities cost because the annual pasture-based system did not have a structure for cow housing (Table 20). Production costs for the seasonal pasture with AD and additional land for cash cropping decreased $252,479/yr because of $820,934/yr decrease in net purchased feed and bedding cost compared to the confinement system. There were 2,942 t DM/yr feed sold compared to 60 t DM/yr sold by the confinement farm. The return from feed and cash crop sales more than offset the increased costs of custom hire, seed, fertilizer and chemicals, and land rental (Table 20). The addition of the anaerobic digester on the seasonal farm with additional land for cash cropping increased facilities cost by 108% (92,361/yr) and labor cost by 27% ($17,618/yr) compared to the seasonal pasture without AD. Energy cost decreased by 34% ($6,903/yr) compared to the seasonal farm without AD and without an expanded land base. Comparing a seasonal farm with cash crop and imported manure without AD with the representative seasonal farm with expanded cash crop, imported manure and AD there was a reduction in energy cost by 68% ($28,321/yr). This included a 16% decrease ($1,318/yr) in energy for manure handling for the reduction in the amount of purchased bedding from 1.4 kg/cow/day (3 lb/cow/day) to 0.4 kg/cow/day (1 lb/cow/day). There was a 33% ($2,346/yr) decrease in energy for milking and 95 milk cooling related to water heating that was partially replaced by gas from the digester. Energy for animal housing, ventilation and lighting ($1,500/yr) was completely offset the biogas produced by the AD. The major reduction of energy costs with the AD was a reduction of 24% ($3,971/yr) in electricity purchased (production of resource inputs). Additionally, there was 352,783 MBtu/yr more electricity produced than consumed by the farm, and this was sold. However, the selling price was the same as the buying price which over-estimated the farm selling price. The revenue from electricity sold was $9,878/yr. The confinement system with AD experienced an increase in facilities costs of 24% ($20,129/yr) and labor by 21% ($15,885/yr) due to the anaerobic digester. Bedding costs decreased 20% ($4,377/yr). Energy cost was reduced by 76% ($16,523/yr). 4.2.3. Income and net return Income from milk sales was higher in the seasonal pasture system ($520,062/yr) followed by confinement ($450,900/yr) and the annual pasture ($443,650/yr). The annual milk production of the farms was 8,482 kg/cow for the seasonal pasture system, 9,946 kg/cow for the confinement system and 6,829 kg/cow for the annual pasture-based system. Even though the confinement had higher milk production per cow, the income from milk sales was higher for seasonal pasture farm because it had more lactating cows than the confinement farm. Income from animal sales increased 36% ($22,155/yr) with the seasonal pasture system and 30% ($18,752/yr) with the annual pasture-based system compared to confinement (Table 21). The difference was related to the culling rate; 25% for the seasonal pasture, 30% for the annual pasture, and 35% for the confinement system. 96 Table 21. Income and net return to management and unpaid factors ($/year) representative dairy production systems Seasonal Confine Seasonal Confine pasture w cash AD pasture crop and AD Income from milk sales 450,900 451,160 520,062 519,862 Income from animal sales 61,655 61,655 83,810 83,810 Livestock expenses ($/cow-yr) 551 551 359 359 Return to management and 73,594 62,578 86,133 420,192 unpaid factors for five Annual Pasture 443,650 80,407 418 88,162 Return to management and unpaid factors varied depending on the farming system (Table 21). The seasonal pasture with AD and cash crop production had the greatest net return to management and unpaid factors, followed by the annual pasture, seasonal pasture, confinement and confinement with AD. Seasonal pasture with additional land for cash cropping and AD had the highest net return because it had the lowest production cost ($183,481/yr) and the highest income from milk ($519,862/yr) and animal sales ($83,810/yr) which were 70% less, and 15% and 36% more, respectively, than the confinement dairy. The farm had a net return to management and unpaid factors of $334,059/yr greater than the seasonal dairy, indicating returns from both the AD and cash crop sales. The confinement farm with AD had the lowest net return to management and unpaid factors because of the high production cost ($450,238/yr) which included an increase of $14,278 per year from the AD. The addition of the AD on the confinement farm reduced the net return to management and unpaid factors by $11,016/yr. The annual pasture and seasonal pasture had similar net returns (Table 21). The confinement system had a lower net return to management and unpaid factors compared to the annual pasture and seasonal pasture systems because it had $20,500/yr less income from animal sales. 97 4.3. Environmental impact The evaluation of the environmental impact focused on: 1) nutrient balance and nutrient loss to the environment, 2) emissions of ammonia, hydrogen sulfide, methane, nitrous oxide, biogenic carbon dioxide and combustion of carbon dioxide) and 3) environmental footprints (water, reactive nitrogen loss, energy use and greenhouse gas emissions). The analysis links the environmental impact with the type of dairy housing and management system (confinement, seasonal pasture or annual pasture) and the integration of an anaerobic digester on confinement and seasonal pasture dairies. 4.3.1. On-farm nutrient cycling Nutrients that flow through the farm either accumulated in the soil or were lost to the environment. The whole-farm mass balance of nitrogen, phosphorus and potassium was determined as the sum of all nutrient imports in feed, fertilizer, manure deposition and legume fixation minus the exports in milk, feed, animals, manure, and losses to the environment (Figure 11). The quantity and nutrient content of the manure produced was a function of the quantity and nutrient content of the feeds consumed. Total manure nitrogen consisted of organic and ammoniacal nitrogen (NH3-N). During manure handling, ammoniacal nitrogen was transformed and volatilized as ammonia (Figure 7). 98 Figure 7. Integrated Farm System Model Overview (USDA, 2013) An embedded soil model was used to predict moisture and nitrogen available for the growth and development of each crop. Each soil layer included nitrate, ammonia, crop residue nitrogen, manure organic nitrogen, and other soil organic matter. Nitrogen uptake by the crop was limited by availability or demand of the crop. In the confinement and seasonal farms all manure collected in the milking parlor and barn was applied to land going to corn production. Nitrogen from legumes and manure applied by the grazing animals supplied the nutrients for the grass pasture. In the annual pasture-based dairy, 80% of manure collected in the milking parlor was applied to grass and 20% to alfalfa. Daily nitrogen losses from the soil were from volatilization, leaching and denitrification (Figure 8). Nitrogen volatilization losses occurred in the barn, during storage, following field application and during grazing. Denitrification and leaching losses were related to the rate of 99 moisture movement and drainage from the soil profile as influenced by soil properties, rainfall, and the amount and timing of manure and fertilizer applications. Erosion of sediment was a function of daily runoff depth, peak runoff rate, field area, soil erodibility, slope, and soil cover. Phosphorus transformation and movement were among surface and subsurface soil pools of organic and inorganic P. Surface processes included surface application, runoff, and transformation along with soil-surface interactions through infiltration and tillage. Runoff losses of sediment-bound P and soluble P were influenced by manure and tillage management as well as daily soil and weather conditions. Amonification NO : N O NOX : N2O NH4 Nitrification Plant N Microbial N uptake inmobilization X NO 3 Plant N uptake 2 Denitrification N 2 Nitrogen fixation Organic Nitrogen Microbial N inmobilization Figure 8. Conceptual model of controls on N gas emissions from soil (modified from Parton et al., 2001) The nutrient balance included the crop nutrients available on-farm (N, P, K) and crop nutrient removal over that available on the farm, and included annual soil P and K build-up or 100 depletion. Nutrient balance was influenced by the cropping system and the area designated for each one (Table 22). Table 22. Land area of five representative dairy production systems (ha) Confine Seasonal Seasonal pasture w Confine AD pasture cash crop and AD Total land 111 111 111 809 Alfalfa area 36 36 10 10 Grass area 0 0 51 51 Corn area 75 75 51 374 Soybeans area 0 0 0 374 4.3.2. Confinement systems Annual Pasture 111 40 71 0 0 4.3.2.1. On-farm nutrient cycling On the confinement farms most of the nutrients were imported through purchased feed (such as soybean meal, distillers grain, minerals and vitamins), fertilizer, and legume fixation. Twenty-eight kilograms per hectare (25 lb/ac-yr) of nitrogen was applied to the corn at planting time. To supply the N, P and K required by the corn, all manure was applied to land going to corn production. The export of nutrients was through sales of milk, animals and feed, and losses such as nitrogen volatilization, denitrification and leaching, and P and K loss through runoff. There was also carbon loss as carbon dioxide, methane and through runoff. Both confinement farms (with and without AD) had similar nutrient imports and exports, nutrients available on-farm, nutrient crop removal, nutrients build-up or depletion (Table 23) and nutrients loss (Table 24). When the AD was introduced there was a reduction in potassium import because a portion of the bedding was recycled so less bedding was purchased. 101 Table 23. Annual nutrient cycling on five representative dairy farms. Unit Confine Confine AD Nutrients imported and exported N imported kg/ha 195 195 N exported kg/ha 83 84 P imported kg/ha 12 12 P exported kg/ha 14 14 K imported kg/ha 26 15 K exported kg/ha 28 28 Nutrients available on farm N kg/ha 298 293 P kg/ha 19 19 K kg/ha 108 97 Nutrients crop removal over that available on farm N % 60 61 P % 115 117 K % 101 112 Nutrients build up or depletion P build-up kg/ha 0 0 P depletion kg/ha 2.2 2.5 K build-up kg/ha 0 0 K depletion kg/ha 7.1 17.8 Seasonal pasture Seasonal pasture w cash crop and AD Annual Pasture 326 79 23 14 72 21 212 123 16 16 41 31 342 76 22 11 52 27 479 31 193 235 17 59 500 30 195 46 76 76 60 105 80 46 64 83 9.0 0 41.9 0 0 0.2 10.2 0 11.2 0 14.6 0 Table 24. Nutrient loss to the environment on five representative dairy farms (kg/ha-yr). Confine Confine Seasonal Seasonal Annual AD pasture pasture w/cash pasture crop and AD Nitrogen lost by volatilization 76.3 78.4 166 34.9 157 Nitrogen lost by leaching 12.1 11.1 51.3 11.5 19.4 Nitrogen lost by denitrification 8.1 7.2 40.6 6.7 12.2 Phosphorous loss in runoff and 0.34 0.34 0.22 0.56 0.00 leachate Potassium loss through runoff 5.38 4.82 9.64 2.91 9.75 Carbon loss as carbon dioxide 6,194 6,044 5,380 8,857 7,869 Carbon loss as methane 209 189 250 31 197 Carbon loss through runoff 1.3 1.3 1.3 1.5 0.3 102 4.3.2.1.1. Potassium Adding the AD on the confinement farm decreased the amount of K imported from 26 kg/ha-yr to 15 kg/ha-yr, and on-farm nutrient availability decreased from 108 kg/ha-yr to 97 kg/ha-yr (Table 23) because chopped straw bedding purchases decreased from 1.4 kg/cow-day to 0.5 kg/cow-day as a portion of the bedding was separated and recycled. Overall, K exports did not change although there was a small decrease in K runoff related to the reduction in manure volume with the AD digestate. The land area available and crops produced were selected to provide the forage and corn grain for the herd with only small amounts purchased or sold. The cropping system on the confinement farm caused a small, long-term, K depletion (7.1 kg/ha-yr) which would require periodic purchases of commercial K to correct. When the AD was added and less bedding was imported the soil K depletion increased to 17.8 kg/ha-yr. This need for additional fertilizer would kg/ha-yr offset a portion of the savings from the reduction in purchased bedding (Figure 9). 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 Confine P build up P depletion Confine AD Seasonal pasture K build up K depletion Seasonal pasture w cash crop and AD Figure 9. Soil phosphorous and potassium build up and depletion 103 Annual Pasture 4.3.1.1.2. Nitrogen Nitrogen imported to farm was the same in both confinement farms (195 kg/ha-yr). Nitrogen was mainly imported through purchased soybean meal and distillers grain. In addition 28 kg/ ha-yr (25 lb/ac-yr) of nitrogen was imported as fertilizer for corn land. Alfalfa and pasture legumes imported N to the farm through N fixation. Perennial and forage legumes, such as alfalfa and white clover may fix 280-560 kg of nitrogen per hectare (Lindemann and Glover, 2003). Nitrogen crop removal over that available on farm was 60%-yr, allowing between 293 and 298 kg/ha-yr of N available on farm (Table 23). The export of N was through milk, animals, alfalfa silage and hay sold. Nitrogen also had losses, most of all through volatilization (76.3 to 78.4 kg/ha-yr) that occurred in the barn, during storage and field application (Table 24). There were also some losses through denitrification and leaching which were related to soil properties and the amount and timing of manure and fertilizer applications. 4.3.1.1.3. Phosphorus Phosphorous imported to the farm was the same on both confinement farms (12 kg/hayr). It was primarily imported through purchased soybean meal and distillers grain. Phosphorous crop removal was between 115 and 117%-yr over that available on farm, allowing 19 kg/ha-yr of P available on farm (Table 23). The export of P was through milk, animals, feed sold and losses through runoff and leachate (0.34 kg/ha-yr) (Table 24). The low P available on farm and the exports and losses produced a small P depletion between 2.2 and 2.5 kg/ha-yr (Table 23, Figure 9). 104 4.3.2.2 .Environmental emissions Greenhouse gas emissions of carbon dioxide, methane, and nitrous oxide in addition to ammonia and hydrogen sulfide originating from manure on the barn floor, the manure storage structure and field applied manure were evaluated. The major emissions from each of the dairies (from highest to lowest) were: methane, combustion carbon dioxide, ammonia, nitrous oxide, hydrogen sulfide and, biogenic carbon dioxide (Table 25). Table 25. Environmental emissions of five representative dairy production systems Confine Confine Seasonal Seasonal AD pasture pasture w cash crop and AD Ammonia Total farm (kg/yr) 10,340 10,619 22,436 35,068 Total farm (kg/ha-yr) 93 96 202 43 Hydrogen Sulfide Total farm (kg/yr) 326 313 264 1,043 Total farm (kg/ha-yr) 2.9 2.8 2.4 1.3 Methane Total farm (kg/yr) 31,001 28,062 37,192 37,582 Total farm (kg/ha-yr) 279 253 335 46 Nitrous Oxide Total farm (kg/yr) 486 468 934 1,662 Total farm (kg/ha-yr) 4.4 4.2 8.4 2.1 Biogenic Carbon Dioxide Net emission (kg/yr) -365,875 -357,925 -422,615 1,745,611 Net emission (kg/ha-yr) -3,296 -3,225 -3,807 2,158 Combustion CO2 Total farm (kg/yr) 35,683 30,210 29,864 20,371 Total farm (kg/ha-yr) 321 272 269 25 Annual Pasture 21,234 191 40 0.4 29,174 263 630 5.7 -347,118 -3,127 24,093 217 4.3.2.2.1. Carbon dioxide and methane emissions Carbon loss as carbon dioxide was the greatest source of carbon loss in the total confinement dairy systems. Ninety-five percent of the total carbon loss was lost as biogenic CO2 105 (Figure 10, Table 24) which was from plant, animal and microbial respiration from soil and stored manure. Most of the biogenic carbon dioxide emissions originated in the housing facilities from animal respiration and decomposition of organic matter in manure on floors in the barn (Table 26). Confinement barn emissions were greater than the systems incorporating grazing because of the extended period of time the animals were in the barn. When the AD was added biogenic carbon dioxide emissions increased in manure storage (Table 26) because carbon dioxide was released in the combustion of methane during anaerobic digestion. There was a small decrease in biogenic carbon dioxide assimilated in feed because of the reduction in manure during the digestion process. The result was a small decrease in biogenic carbon dioxide with the AD. Table 26. Biogenic carbon dioxide emissions of five representative dairy production systems (kg/yr) Confine Confine Seasonal Seasonal Annual AD pasture pasture w cash Pasture crop and AD Housing facility 685,552 685,496 555,488 554,272 504,026 Manure storage 42,479 241,471 26,921 212,444 0 Assimilated in feed -1,093,905 -1,284,892 -1,249,702 734,613 -1,069,259 Grazing animal 0 0 244,678 244,282 218,114 Net emission -365,875 -357,925 -422,615 1,745,611 -347,118 Net emission (kg/ha-yr) -3,296 -3,225 -3,807 2,158 -3,127 Other major sources of CO2 emission were from fuel combustion (Table 25) related to field operations such as tillage, planting, harvesting and other operations requiring mechanization. Adding the AD lead to a 2% reduction in carbon loss as carbon dioxide and a 9% reduction of carbon loss as methane. Each decrease was related to the conversion of methane to biogas for electricity generation or water heating. The major source of methane was the long term manure storage. Because the manure storage structure served as short-term storage to hold 106 manure before being deposited in the digester, carbon loss as methane decreased as the manure storage period decreased (Table 24). Major sources of methane emissions were from enteric fermentation and long term manure storage with minor sources being in the barn floor and field applied manure. The dairy cattle were the main source of methane emissions for each of the confinement dairies (Table 27). The long term manure storage facility was also an important source of methane. The addition of the anaerobic digester on the confinement farm decreased methane emission from the manure storage structure by 26% (from 11,274 kg/yr to 8,360 kg/yr) by enclosing the manure in a tank where the methane was converted to biogas (Table 27). Table 27. Methane emissions of five representative dairy production systems (kg/yr) Confine Confine Seasonal Seasonal AD pasture pasture w cash crop and AD Housing facility 19,690 19,661 20,115 20,238 Manure storage 11,274 8,360 7,070 7,118 Field application 38 40 71 203 Grazing 0 0 9,936 10,022 Total farm 31,001 28,062 37,192 37,582 Total farm (kg/ha-yr) 279 253 335 46 Annual Pasture 19,497 0 39 9,638 29,174 263 4.3.2.2.2. Ammonia emissions Ammonia is produced when microbes breakdown protein and other nitrogen containing compounds during decomposition causing an increase in pH (Hoeksema et al., 2012). In raw manure there is a balance between ammonium concentration and volatile fatty acid concentration which results in a pH near neutral. When volatile fatty acids are reduced during anaerobic digestion, pH increases (Paul and Beauchamp, 1989) so pH is normally higher in digestate than in raw manure. Volatile ammonia is formed (NH3), which could be up to 25% of the ammonium 107 fraction (Scottish Executive Environment and Rural Affairs Department, 2007). Most of the ammonia emissions from the confinement farms originated from manure on the milking center and barn floors, manure storage structures and following field application (Table 28). Because of the increased volatility there was a small increase in ammonia emissions with AD. Table 28. Ammonia emissions of five representative dairy production systems (kg/yr) Confine Confine Seasonal Seasonal Annual AD pasture pasture w cash Pasture crop and AD Housing facility 4,310 4,217 6,773 6,804 15,150 Manure storage 2,172 2,315 4,549 5,153 0 Field application 3,859 4,086 7,151 19,106 2,309 Grazing 0 0 3,963 4,005 3,774 Total farm 10,340 10,619 22,436 35,068 21,234 Total farm (kg/ha-yr) 93 96 202 43 191 4.3.2.2.3. Nitrous oxide emission Nitrous oxide emissions originate primarily from nitrification and denitrification processes in the soil, and also in the crust of the slurry manure storage (Rotz et al., 2011a). Nitrous oxide has a global warming potential 298 times that of carbon dioxide, making it the strongest of all greenhouse gas emissions in agricultural production (IPCC, 2007). Nitrous oxide emissions can be greater where manure remains for longer periods where nitrification or denitrification converts ammonium to nitrate or nitrate to atmospheric N2 (Figure 8) (IPCC, 2007). On the confinement farms nitrous oxide emissions originated primarily in the housing facilities, manure storage and farmland (Table 29). The pH of digested manure is typically higher thereby supporting nitrous oxide reduction. The addition of an AD on the confinement farm decreased the total farm emissions of nitrous oxide by a small amount (4%). Manure on the free 108 stall barn floor is typically a minor source of nitrous oxide emission (Rotz et al., 2011a) but some enteric nitrous oxide could also be emitted by the animals (Hamilton et al., 2010). Table 29. Nitrous oxide emissions of five representative dairy production systems (kg/yr) Confine Confine Seasonal Seasonal Annual AD pasture pasture w cash Pasture crop and AD Housing facility 204 198 339 375 325 Manure storage 147 143 243 269 0 Farmland 134 126 352 1,019 305 Total farm 486 468 934 1,662 630 Total farm (kg/ha-yr) 4.4 4.2 8.4 2.1 5.7 4.3.2.2.4. Hydrogen sulfide emissions Hydrogen sulfide is a toxic compound that is regulated by the US EPA under the Clean Air Act. Hydrogen sulfide is primarily created and emitted from decomposing manure under anaerobic conditions (Rotz et al., 2011a). The major source of hydrogen sulfide on all dairies was field application of manure (Table 30). On the confinement farms manure was stored under anaerobic conditions beneath the crust formed on the manure surface which increased the hydrogen sulfide emission. The anaerobic digester reduced hydrogen sulfide emissions by 4% because of the recycled bedding and reduction of manure handled after the digestion process. The confinement farm handled 3,155 t DM/yr of manure but when an anaerobic digester was used the amount of manure handled was reduced to 3,102 t DM/yr. 109 Table 30. Hydrogen sulfide emissions of five representative dairy production systems (kg/yr) Confine Confine Seasonal Seasonal Annual AD pasture pasture w cash Pasture crop and AD Housing facility 35 34 30 29 39 Manure storage 63 61 50 49 0 Field application 228 218 184 964 0 Grazing 0 0 0 0 0 Total farm 326 313 264 1,043 40 Total farm (kg/ha-yr) 2.9 2.8 2.4 1.3 0.4 4.3.2.3. Environmental footprints Environmental footprint is a measure of the demand on the ecosystem services of the earth. Footprints were evaluated for water, reactive nitrogen, energy, and greenhouse gas emissions. The footprints were determined by summing the estimates for each of the uses (removing those allocated to co-products), and dividing by the amount of milk produced. Water was mainly used for the production of feed crops, drinking water for animals, animal cooling, cleaning of the parlor and holding areas on dairy farms. Reactive nitrogen is essential in the growing of crops and feeding of animals. Primary losses of reactive nitrogen include ammonia and nitrous oxide emissions to the atmosphere, nitrate leaching to ground water, and the combustion of fuels. The energy footprint was the total energy required to produce feed and milk which includes all fuel and electricity directly used in the production system as well as the secondary energy used in the production of resources used on the farm. The carbon footprint was determined as the net emission of the three GHG’s including all sources and sinks of CO2, so a portion of the CO2 assimilated in the feed is in the carbon exported during feed, milk, and animal productions. 110 4.3.2.3.1. Water footprint In all dairies the major sources of water footprint were: feed production with rainfall, followed by production of purchased feed and inputs (Table 31). There was a 28% reduction in water use for purchased feed and inputs when the AD was used on the confinement farm because of the reduction in purchased bedding. Because less bedding was purchased less water was required for the production of bedding. Even though straw is a by-product of harvest it requires water for growth. Table 31. Water footprints of five representative dairy production systems Unit Confine Confine Seasonal Seasonal AD pasture pasture w cash crop AD Feed production, t/yr 585,780 585,935 585,746 1,008,009 rainfall Drinking t/yr 2,810 2,810 4,193 4,185 Animal cooling t/yr 228 228 324 324 Parlor, equipment t/yr 913 913 1,296 1,295 cleaning Production of t/yr 128,317 92,701 326,354 328,487 purchased feed and inputs Not allocated to t/yr -122,454 -117,049 -160,046 -200,348 milk production Water footprint kg/kg 600 569 630 905 with rainfall FPCM-yr Water footprint kg/kg 99 68 195 170 without rainfall FPCM-yr Water footprint w kg/kg 5.4 5.1 5.7 1.1 rainfall per ha FPCMha-yr Annual Pasture 584,965 3,977 365 1,460 335,579 -144,650 716 244 6.4 The water footprint decreased 4% with AD evaluated as the water footprint not allocated to milk production (Table 31). Water used in the production of machinery, fertilizer, pesticides, and plastic was considered to be insignificant (Rotz et al., 2011a). Water use for drinking, animal cooling and parlor and equipment cleaning on all farms increased with the number of cows. 111 4.3.2.3.2. Energy footprint The major sources of energy use footprint were production of resource inputs, milking and milk cooling, feed production, animal feeding, manure handling and animal housing ventilation and lighting (Table 32). The confinement farms had the highest energy use in feed production (215,987 MJ/yr) because it produced 36 to 54% more feed than the seasonal and annual pasture farms. Because animals were kept in the barn all year, animal feeding (152,438 MJ) and animal housing ventilation and lighting (57,779 MJ/yr) were also the greatest energy demands of all the farms (Table 32). Table 32. Energy footprint of five representative dairy production systems Unit Confine Confine Seasonal Seasonal AD pasture pasture w cash crop AD Feed production MJ 215,987 215,862 141,373 190,568 Animal feeding MJ 152,438 151,968 122,344 120,557 Manure handling MJ 74,329 64,052 67,626 256,978 Milking, milk MJ 232,312 155,099 267,928 179,039 cooling Animal housing MJ 57,799 57,799 56,576 56,444 ventilation, lighting Production of MJ 1,906,139 1,249,329 2,159,025 2,478,746 resource inputs Not allocated to MJ -451,019 -338,499 -533,488 -571,014 milk production Energy footprint MJ/kg 2.2 1.6 1.9 2.1 FPCM Energy footprint MJ/kg 0.02 0.01 0.02 0.003 per ha FPCM-ha Annual Pasture 115,236 110,996 68,338 228,576 18,091 2,033,489 -434,975 2.0 0.02 Adding the AD on the confinement dairy reduced energy use for manure handling by 14% (10,277 MJ/yr), by reducing the volume of bedding handled and applied as manure. Energy for milking and milk cooling was reduced by 33% (77,213 MJ/yr) as energy for water heating was partially replaced by biogas from the digester. The greatest reduction of the energy footprint 112 was from the reduction in fossil fuel energy used to generate electricity off-farm (production of resource inputs) which was reduced 34% (656,810 MJ/yr). There was also a 25% decrease in energy use not allocated to milk production (allocated to the cattle growth and sold as beef). 4.3.2.3.3. Reactive nitrogen loss footprint The primary sources of reactive nitrogen loss were ammonia emissions, nitrate leaching, nitrous oxide emissions fuel combustion emissions and production of resource inputs (Table 33). Reactive nitrogen is essential to crop and livestock production. The confinement dairy had the smallest reactive nitrogen loss footprint (8.9 g/kg FPCM-yr) (Table 33) because it had the least ammonia emissions, nitrate leaching, nitrous oxide emissions and nitrogen loss during the production of resource inputs. Each of these (except ammonia) was reduced when the AD was used on the confinement farm. Ammonia emissions increased because the pH increased in the digestate, thereby producing more ammonium in the volatile form. Nitrate leaching decreased because less manure was being applied to the land. Nitrous oxide emissions decreased because the higher pH in the digestate allowed nitrous oxide reduction from ammonium or nitrate to nitrous oxide. Nitrous oxide emissions due to fuel combustion were also reduced on the confinement farm with AD because less manure was being handled (Table 33). Combustion of fossil fuel releases nitrogen oxides to the atmosphere which increase with field operations that require more tillage, planting and harvesting. 113 Table 33. Reactive nitrogen loss footprint of five representative dairy production systems Unit Confine Confine Seasonal Seasonal Annual AD pasture pasture w Pasture cash crop AD [a] kg 8,496 8,725 18,439 57,912 17,447 Ammonia em Nitrate leaching kg 1,343 1,239 5,711 19,234 2,164 Nitrous oxide em kg 309 297 594 2,165 401 Fuel combustion kg 118 100 94 644 76 em Production of kg 428 352 1,052 1,941 1,135 resource inputs Not allocated to kg -1,825 -1,827 -3,690 -10,617 -3,045 milk production Reactive nitrogen g/kg 8.9 8.9 18.5 30.1 16.7 footprint FPCM Reactive nitrogen g/kg 0.1 0.1 0.2 0.04 0.1 footprint per ha FPCM-ha [a]: em= emission 4.3.2.3.4. Carbon footprint The carbon footprint measures total GHG emissions expressed in CO2 equivalent units (CO2e). The primary contributors to the carbon footprint were animal emissions (25 to 59% of total GHG), manure emissions (9 to 34% of total GHG), production of resource inputs (9 to 23% of total GHG), emissions during feed production (2 to 7% total GHG) and fuel combustion emissions (1 to 3% of total GHG) (Table 34). The confinement dairies had the lowest animal emissions because animal respiration was based on daily intake of feed dry matter (Rotz et al., 2011a). Because animals in confinement consume less forage in the diet than grazing animals, carbon dioxide emissions decreased. When using an AD, carbon dioxide emissions from manure decreased because methane emissions were reduced by containing all manure in a closed tank where it was converted biogas. The carbon 114 footprint associated with the production of resource inputs decreased by 31% because of the reduction of fossil fuel used to generate electricity off-farm. Table 34. Carbon footprint of five representative dairy production systems Unit Confine Confine Seasonal Seasonal AD pasture pasture w cash crop AD [a] kg 481,602 481,395 741,392 1,493,521 Animal em Manure em kg 397,334 321,179 360,953 766,547 Emission during kg 35,444 33,248 96,815 132,907 feed production Net biogenic carbon kg -365,550 -357,610 -422,188 2,928,001 dioxide em Fuel combustion em kg 35,652 30,184 29,837 40,706 Production of kg 206,787 142,209 263,018 537,109 resource inputs Not allocated to kg -193,915 -171,407 -244,488 -489,918 milk production Carbon footprint kg/kg 0.97 0.84 1.04 1.00 without biogenic FPCM CO2 Carbon footprint kg/kg 0.66 0.54 0.72 2.10 FPCM with biogenic CO2 Carbon footprint kg/kg 0.006 0.005 0.006 0.003 FPCMwith biogenic CO2 ha per ha [a]: em= emission Annual Pasture 716,839 108,683 82,809 -346,810 24,072 278,397 -191,363 0.93 0.65 0.006 4.3.3. Seasonal pasture farms 4.3.3.1. On-farm nutrient cycling Most of the nutrients were imported on the seasonal pasture dairies were from purchased feed (such as hay, soybean meal, distillers grain, and minerals and vitamins), fertilizer, manure application and forage legume nitrogen fixation. All manure collected in the milking parlor and barn was applied to land going to corn production and twenty-eight kilograms per hectare (25 lb/ac) of commercial nitrogen fertilizer was applied to corn at planting time. Nitrogen from legumes and manure applied by the grazing animals supplied the nutrients for the grass pasture. 115 The exports of nutrients were through milk, animals and feed sold. Ten percent of the feed produced on the seasonal farm was sold and it was increased to 87% when additional land was acquired to accommodate the additional manure required for the AD. Some nutrients were the lost to the environment through nitrogen volatilization, denitrification, leaching, and loss of phosphorous and potassium through runoff. There were also carbon losses leaving the farm as carbon dioxide, methane or through runoff. Nutrient cycling was different on the seasonal pasture farms because the land use and cropping system was different. The seasonal pasture had a 111 ha land base which expanded to 809 ha when cash crops were produced (Table 22). 4.3.3.1.1. Potassium The seasonal pasture had the greatest soil potassium build up (41.9 kg/ha-yr) (Figure 9). Potassium imports (72 kg/ha-yr) (Table 23) were from the purchase of 13 t of hay (Table 20) following the shift of 26 ha of land for alfalfa production to land for grazing animals (Table 22). Potassium was also imported with purchase of chopped straw for bedding which contained nitrogen, phosphorous and potassium (Shaver and Hoffman, 2010). The seasonal farm also exported less potassium (21 kg/ha-yr), allowing potassium availability on-farm of 193 kg/ha-yr. The seasonal farm with an expanded land base for cash crop production and AD had greater K exports (compared to the other farms) because 87% of the total crop production was sold (Table 23). The increase in pasture land also decreased potassium loss to the environment (Table 24). 4.3.3.1.2. Nitrogen The seasonal pasture dairy imported more nitrogen per unit area than the seasonal farm with AD and additional land for cash crop production (Table 23) because relatively more 116 bedding and feed were purchased. A greater percentage of the land was in alfalfa and grass/legume production, thereby increasing nitrogen import by fixation. 550 450 kg/ha 350 250 150 50 -50 Confine Confine AD Seasonal pasture Nitrogen available on farm Phosphorous available on farm Seasonal pasture w cash crop and AD Annual Pasture Figure 10. Nutrients available on farm 140 120 % 100 80 60 40 20 0 Confine Confine AD Seasonal pasture N crop removal over that available on farm P crop removal over that available on farm K crop removal over that available on farm Seasonal pasture w cash crop and AD Figure 11. Nutrients crop removal over that available on farm. 117 Annual Pasture The seasonal pasture dairies had the greatest nitrogen loss to the environment (258 kg/hayr). The losses were from leaching (51 kg/ha-yr), denitrification (40.6 kg/ha-yr) and volatilization (166 kg/ha-yr) (Figure 12). Denitrification and leaching losses from the soil were related to the rate of moisture movement and drainage from the soil profile as influenced by soil properties, rainfall, and the amount and timing of manure and fertilizer applications. There was more nitrogen loss by leaching because the urine deposited in the pasture had high concentrations of nitrogen which could exceed plant uptake (Table 24). Nitrogen lost through volatilization was the greatest source of loss on all the dairies (Figure 12). Nitrogen is the most abundant nutrient in manure and the seasonal pasture dairy had the highest nitrogen lost by volatilization (166 kg/ha-yr) (Table 24) because of losses from manure in the barn, milking parlor, during land application and from the urine and manure deposited by the cattle. On a unit area basis, nitrogen losses were reduced by 79% on the seasonal pasture with cash crop and AD compared to the seasonal pasture dairy (Figure 12, Table 24). Because of the increased land for cash crop production more nitrogen was used for crop production compared to that available on-farm. 118 300 250 kg/ha-yr 200 150 100 50 0 Confine Confine AD Nitrogen lost by denitrification Nitrogen lost by leaching Nitrogen lost by volatilization Seasonal pasture Seasonal pasture w cash crop and AD Annual Pasture Figure 12. Nitrogen lost to the environment of five representative dairy production systems 4.3.3.1.3. Phosphorous The seasonal pasture dairy had a greater phosphorous build-up (9.0 kg/ha-yr) because the P imported in feeds (primarily grain and concentrates) and bedding exceeded P exports in sales of meat, milk and excess feed (Table 22). The seasonal pasture with additional land for cash crop production and AD had greater P loss in runoff and leachate related to soil erosion and tillage of the crop land. Most of the P loss occurred with rainfall after land application of manure. Phosphorus imports equaled P exports and there was no long-term soil build-up or depletion. 4.3.3.2. Environmental emissions Gaseous emissions from the seasonal pasture farms in rank order (from high to low) were: methane, combustion carbon dioxide, ammonia, nitrous oxide, hydrogen sulfide and, biogenic carbon dioxide (Table 25). When additional land was added with an AD the carbon dioxide released by the combustion of methane was offset by a reduction in carbon dioxide 119 emission (20,371 kg/yr) from soil respiration. The major emissions from this farm were biogenic carbon dioxide (1,745,611 kg/yr) from the combustion of biogas (Table 25). 4.3.3.2.1. Carbon dioxide and methane emissions The seasonal pasture with additional land for cash crop production and AD had the greatest carbon loss as carbon dioxide (8,857 kg/ha-yr) (Table 24) because any remaining biogas that was not used for either electricity generation or water heating was burned off in a flare. Most of the biogenic carbon dioxide emissions on the seasonal pasture farm were from housing facilities related to animal respiration and manure on floors in the barn (Table 26). The grazing animals also increased biogenic carbon dioxide emissions (Table 26) because animal respiration was based on daily intake of feed dry matter (Rotz et al., 2011a). Because grazing animals consumes higher forage diets, carbon dioxide emission increased. The greatest biogenic carbon dioxide emissions in the seasonal pasture with expanded cash crop and AD farm was because of the assimilation in feed due to the increased crop land. Croplands usually assimilate C from CO2 in the atmosphere, but also emit CO2 through plant (autotrophic) and soil (heterotrophic) respiration (Chianese et al., 2009a). Biogenic carbon dioxide emission in manure storage increased also increased in this farm (Table 26) because this emission includes the carbon dioxide created through combustion of methane. The seasonal pasture with cash crop production and AD had the lowest carbon loss as methane (31 kg/ha-yr). Major sources of methane included long term storage and because storage time was reduced by holding the manure for a short time before placing it in the digester carbon loss as methane decreased (Table 24). The seasonal pasture farms had greater housing methane emissions than the confinement farm because grazing cows consumed more forage. The 120 enteric methane emissions per cow increase with the percentage of fiber that was fed in the diet cow (Chianese et al., 200c). Grazing animals in seasonal and annual pasture dairies increased methane emissions (9,630 to 10,022 kg/yr) because of the excreted feces and urine that were deposited on pastures (Table 27). Some studies have shown that feces are a small but significant source of methane and that emissions from urine are similar to background soil emissions (Jarvis et al., 1995; Yamulki et al., 1999). 4.3.3.2.2. Ammonia emissions Ammonia emissions (22,436 kg/yr) from the seasonal pasture dairy were more than double that of the confinement farms (Figure 13, Table 28). Emissions from the housing facilities, manure storage and field application increased because there were more animals in the seasonal pasture system (142-cows) than the confinement system (100-cows), therefore more manure and urine was produced in these farms. kg/yr Ammonia 40000 35000 30000 25000 20000 15000 10000 5000 0 Confine Grazing Manure storage Confine AD Seasonal pasture Field application Housing facility Seasonal pasture w cash crop and AD Annual Pasture Figure 13. Ammonia emissions of five representative dairy production systems 121 The seasonal pasture with additional land for cash crop production and AD had the greatest ammonia emissions (35,068 kg/yr) because of the amount of manure applied to field (Figure 13, Table 28). Also, there was an increase in ammonia emissions as a result of the anaerobic digestion process due to an increase in slurry ammonium-N content. 4.3.3.2.3. Nitrous oxide emissions The seasonal pasture with additional land for cash crop production and AD had the greatest emission of nitrous oxide (1,662 kg/yr) because of the additional nitrogen input on the additional crop land which increased farmland emissions (1,019 kg/yr) (Figure 14, Table 29). kg/yr Nitrous oxide 1800 1600 1400 1200 1000 800 600 400 200 0 Confine Confine AD Farmland Manure storage Housing facility Seasonal pasture Seasonal pasture w cash crop and AD Annual Pasture Figure 14. Nitrous oxide emissions of five representative dairy production systems. The seasonal pasture with cash crops and AD had greater nitrous oxide emissions in the housing facilities (375 kg/yr). Nitrous oxide emissions can be greater where manure remains for longer periods as in the grazing areas. Manure on the floor of free stall barns appears to be a 122 negligible source of nitrous oxide emission (Rotz et al., 2011a), but a small amount of enteric nitrous oxide is emitted by the animals (Hamilton et al., 2010) (Table 29). Nitrous oxide emissions from the manure storage were from the natural crust that was formed on the stored slurry (Chianese et al., 2008b). The seasonal pasture dairies released more nitrous oxide (243 to 269 kg/yr) than the confinement dairies (143 to 147 kg/yr) (Table 29) because manure was collected less frequently during grazing season than in confinement storage. 4.3.3.2.4. Hydrogen sulfide emissions The seasonal farm with AD and cash crops had the greatest hydrogen sulfide emissions (1,043 kg/yr) (Figure 15, Table 30). The major source of hydrogen sulfide was land application of manure (184 to 964 kg/yr). The seasonal pasture dairy had the lowest emissions from field application (184 kg/yr) because less manure was collected and applied to the field. The seasonal pasture with cash crops and AD emitted more hydrogen sulfide during field application (964 kg/yr) because: 1) The manure had been in anaerobic conditions (due to the anaerobic digester), encouraging the transformation from sulfide to hydrogen sulfide, and 2) since there was more crop land, more manure was applied on the soil, leading to more emissions. 123 Hydrogen sulfide 1200 1000 kg/yr 800 600 400 200 0 Confine Confine AD Field application Manure storage Housing facility Seasonal pasture Seasonal pasture w cash crop and AD Annual Pasture Figure 15. Hydrogen sulfide emission of five representative dairy production systems. 4.3.3.3 Environmental footprints Water, reactive nitrogen, energy use and greenhouse gas emission footprints were evaluated for the seasonal pasture dairies. 4.3.3.3.1. Water footprint The primary measures of the water footprint were rainfall for feed production followed by production of purchased feeds and inputs (Table 31). The seasonal pasture with additional land for cash crops and AD had the greatest water footprint (905 kg/kg FPCM-yr) due to feed production (sold and consumed) because this dairy had more area for crop production compared to the other dairies (Table 31). The dairy had less water footprint not allocated to milk production (-200,348 t/yr) because the cash crops sold were considered to be exported from the farm. Water used in the production of machinery, fertilizer, pesticides, and plastic was not significant (Rotz et al., 2011a). Water use for drinking, animal cooling and parlor and equipment 124 cleaning was the same for both seasonal farms because it was based on the number of cows (Table 31). 4.3.3.3.2. Energy footprint The transition from a confinement to a seasonal pasture dairy reduced the energy footprint by 14%. There was a reduction of 35% in on-farm feed production, 20% in animal feeding and 8% in manure handling (Table 32). These reductions were related to the shift of 24 ha of corn production to grazing. There was an 18% decrease in energy not allocated to milk production, which was allocated to the cattle growth produced and sold as beef. This was influenced by the relative quantities of milk and cattle sold. The seasonal pasture with additional land for cash crops and AD dairy had the greatest energy use footprint for production of resources inputs (2,478,746 MJ/yr), such as fuel, electricity, machinery, fertilizer, pesticides, seed, and plastic for the additional land for cash crops. The farm also had the greatest energy footprint for manure handling related to the 12,882 wet t/yr of imported manure. However, the seasonal pasture with cash crops and AD dairy had 4% less energy use footprint 2.1 MJ/kg FPCM-yr (fat and protein corrected milk, 4% fat and 3.3% protein) compared to the confinement dairy (2.2 MJ/kg FPCM-yr) which had less area for crop production and an energy use for production resource inputs of 1,906,139 MJ/kg FPCM-yr (Table 32). The decrease in energy footprint was for two reasons: 1) the addition of the anaerobic digester and 2) because the seasonal pasture farm required less energy for feed production and animal feeding than the confinement farm. The addition of the AD on the seasonal farm reduced energy use by 23% (compared to the confinement farm) for milking, milk cooling and water heating. Energy for animal feeding was reduced by 21% and 12% for feed production compared to confinement because of the addition of grazing. 125 4.3.3.3.3. Reactive nitrogen loss footprint The seasonal pasture dairy with cash crops and AD had the greatest reactive nitrogen loss footprint because of ammonia (57,912 kg/yr), nitrate leaching (19,234 kg/yr), nitrous oxide (2,165 kg/yr), production of resource inputs (1941 kg/yr) and fuel combustion emissions (644 kg/yr). Ammonia emissions were higher because more manure was applied (due to the imported manure). Also, there was an increase in ammonia emissions as a result of the anaerobic digestion process. Nitrate leaching, nitrous oxide, combustions emissions and production of resource inputs were increased because of the increased land for cash crop. Combustion of fossil fuels leads to the creation of nitrogen oxides in the atmosphere which increases with field operations that require more tillage, planting and harvesting. 4.3.3.3.4. Carbon footprint The seasonal pasture with additional land for cash crops and AD had the greatest carbon footprint (2.10 kg/kg FPCM-yr) because of biogenic carbon dioxide, which accounted for 50% of the total GHG emissions. This farm also had the highest animal and manure emissions compared to the other dairies (Table 34) because of the 12,882 t/yr of imported manure. Emissions during feed production, fuel combustion and production of resource inputs were also higher due to the expanded land base for cash crop production (Table 34). 4.3.4. Annual Pasture-based farm 4.3.4.1. On-farm nutrient cycling Most of the nutrients on the annual pasture-based farm were imported through purchased feed (such as hay, soybean meal, distillers grain and minerals and vitamins) and nitrogen fixation by alfalfa and legumes in the grass/legume pasture. Nitrogen from legumes and manure applied by the grazing animals supplied the nutrients for the grass pasture. Eighty percent of manure 126 collected in the milking parlor was applied to grass and 20% to the alfalfa land. Nutrient exports were through milk, sales of animals and feed (10% of feed produced was sold), nitrogen volatilization, denitrification and leaching, and loss of phosphorous and potassium through runoff. There were also carbon losses leaving the farm as carbon dioxide, methane or through runoff. 4.3.4.1.1. Potassium Potassium imports (52 kg/ha-yr) (Table 23) were mostly from the purchase of 114 t/yr of dry grain (Table 20) following the shift of land for crop production to land for grazing animals (Table 22). Grains contain less K than do legumes (forages contain 1-3% K; grain contains 0.50.8% K) (Dupchak, 2001), that is why the annual pasture (which purchased dry grain) had less potassium imported than the seasonal farm (which purchased hay and no dry grain). 4.3.4.1.2. Nitrogen The annual pasture-based dairy had more nutrients available on-farm (500 kg/ha-yr) than the seasonal pasture farm (Table 23, Figure 10), because more N was imported through legumes fixation and purchased feed and less N was exported because this farm did not had grain production. The annual pasture-based dairy had higher nitrogen loss from volatilization (157 kg/hayr) and leaching (12.2 kg/ha-yr) than the confinement dairy because the deposited urine could exceed the uptake by plants (Table 24). 4.3.4.1.3. Phosphorous The annual pasture-based dairy had the greatest soil phosphorus build up (11.2 kg/ha-yr) (Figure 9) because beside it was the only farm that had application of manure collected on grass, also there were more imported feeds (primarily grain and concentrates) and less phosphorous 127 was exported through crops that were sold as compared to the other farms (Table 23). This farm did not have P loss in runoff because of the permanent vegetative cover that reduced runoff and erosion (Table 24). 4.3.4.2. Environmental emissions 4.3.4.2.1. Carbon dioxide and methane emissions The annual pasture-based dairy had the second greatest carbon loss as carbon dioxide (7,869 kg/ha-yr) because it had the greatest production of hay (Table 24). Large stacks of hay stored under cover goes through a heating process during the first few weeks of storage. Heating occurs due to the respiration of microbial organisms in the hay. Through respiration, carbohydrates in the plant tissue and oxygen are converted to carbon dioxide, water, and heat (Rotz et al., 2011a). This farm also had the lowest carbon loss through runoff (0.3 kg/ha-yr) because of the permanent vegetative cover. The annual pasture-based farm had biogenic carbon dioxide emissions in the housing facility similar to the seasonal pasture farm (Table 26). Even though the annual pasture did not have housing facilities, biogenic carbon dioxide emissions were produced in the milking parlor by animal respiration and manure on the floor. This farm had less assimilation in feed than the seasonal farm because it did not produce corn. Also, biogenic carbon dioxide released by the grazing animals increased (Table 26) compared to the confinement farm because the animals consumed higher forage diets. Methane emissions on the annual pasture-based farm were similar to the confinement farm. Even though the annual pasture only had a milking parlor as cow housing, similar methane emissions due to enteric fermentation (19,497 kg/yr) were produced because grazing cows 128 consume more forage. Also, this farm did not have methane emissions from manure storage because this farm stacked the manure and applied to land daily. 4.3.4.2.2. Ammonia emissions The annual pasture-based farm had more than twice the ammonia emissions (21,234 kg/yr) as the confinement farm (Table 28). Housing facilities emissions increased (15,150 kg/yr) because there were more animals in annual pasture (160-cows) compared to the confinement (100-cows), therefore more manure and urine was produced in this farm (Table 28, Figure 13). The manure on the milking center floors produced more ammonia than the urine deposited on pasture (3,774 kg/ha-yr). Ammonia emission due to field application was lower in the annual pasture-based dairy (2,309 kg/yr) because less manure was collected and consequently less was applied on the field (2,599 t DM/yr). 4.3.4.2.3. Nitrous oxide emissions The annual pasture-based and seasonal pasture farm had similar nitrous oxide emissions from farmland (Table 29, Figure 14) because manure remained for longer periods in the grazing areas and the annual pasture farm did not have manure storage. 4.3.4.2.4. Hydrogen sulfide emissions The annual pasture did not have hydrogen sulfide emissions in manure storage or field application because the manure was applied daily (Table 30, Figure 15). Without long term manure storage under anaerobic conditions only small amounts of sulfide could be formed. The manure in the milking parlor produced 39 kg/yr of hydrogen sulfide. 129 4.3.4.3 Environmental footprints 4.3.4.3.1. Water footprint The annual pasture-based farm had the second greatest water footprint (716 kg/kg FPCMyr) due to purchased feed and inputs (335,579 t/yr) because 41% of the animal feed consumed was purchased and required more animal and milking supplies, because it had more cows. Water use for drinking, animal cooling and parlor and equipment cleaning was higher for the annual pasture-based farm because it had the greatest number of cows (Table 31). 4.3.4.3.2. Energy footprint The transition from confinement to an annual pasture-based farm reduced the energy footprint by 11%. This decrease was because of a reduction of 47% in feed production, 27% in animal feeding and 9% in manure handling (Table 32). There was also a decrease of 4% in energy not allocated to milk production which was allocated to the cattle weight produced and sold as beef. Additionally, the annual pasture farm had a 69% decrease in energy for animal housing and ventilation compared to the confinement farm because cattle were on pasture or open lots throughout the year. The annual pasture had a greater energy use footprint for production of resources inputs (2,033,489 MJ/yr) because it purchased 41% of the feed for the animals. The 27% reduction in animal feeding and 47% reduction for feed production on the annual pasture-based farm compared to the confinement farm was because of the shift of crop land to grazing land and, consequently, the addition of grazed forage in the diet of the cattle. The seasonal and annual pasture dairies required less energy for manure handling because manure was only collected from the milking parlor and from the barn (for the seasonal pasture). The annual pasture-based dairy has higher energy required for manure handling (68,338 MJ/yr) 130 compared to the seasonal pasture (67,626 MJ/yr) because it hauls manure daily, increasing machinery use and fuel (Table 32). 4.3.4.3.3. Reactive nitrogen loss footprint The annual pasture-based dairy had a 10% lower reactive nitrogen loss footprint than the seasonal farm because ammonia and nitrous oxide emissions, nitrate leaching, fuel combustion and footprint not allocated to milk production were lower (Table 33). Ammonia decreased because this farm did not have a housing facility where manure could produce emissions. Nitrous oxide emissions were less than the seasonal pasture farm because the annual pasture-based farm did not have manure storage. Fuel combustion emission and nitrate leaching were lower than the seasonal farm because the farm only had land for grazing and no crop production. The footprint not allocated to milk production decreased because it was allocated to the cattle weight gain produced and sold as beef. The footprint from the production of resource inputs increased because the annual pasture-based farm purchased 8% more or feed than the seasonal farm (Table 33). 4.3.4.3.4. Carbon footprint The annual pasture-based farm had a carbon footprint similar to the confinement farm (Table 34). Animal, feed production and production of resource inputs emissions were similar to the seasonal pasture. However, the annual pasture-based farm had the lowest manure carbon footprint (108,683 kg/yr) because there was no manure storage or housing facilities and the primary source of emissions of carbon dioxide were from the decomposition of organic matter in manure deposited by animals in the floor of the milking parlor. 131 CHAPTER 5: CONCLUSIONS Five representative dairy production systems were compared to evaluate resource use and conservation, economic and environmental impacts in the transition from total confinement to seasonal-and annual-pasture based systems. The available land base on four farms was held constant at 111 ha, which was the area needed to support 100 large Holstein cows plus replacements with small annual shortage or excess of feed, and a near-balance of phosphorous and potassium from manure cycling on the farm. The land base of a seasonal pasture system was expanded to 809 ha to provide additional land for cash crop production and land application of imported manure used to operate an anaerobic digester. Anaerobic digestion was evaluated on the confinement and seasonal pasture dairies. 1. Based on a whole-farm nutrient balance, the 111 ha land base supported 100 large-frame (726 kg) Holsteins cows on the total confinement farm, 142 medium-frame (590 kg) cows on the seasonal pasture dairy, and 160 small-frame (454 kg) New Zealand type cows with replacements on the annual pasture dairy. 2. The annual pasture-based system had the greatest net return to management and unpaid factors followed by the seasonal pasture and confinement systems. Compared to the total confinement system, net income on the annual pasture increased 20% and 17% on the seasonal pasture. 3. The addition of an anaerobic digester on the 100-cow total confinement dairy decreased the net return to management and unpaid factors by 15%. 4. When anaerobic digestion was added to the seasonal pasture with an increased land base for cash crop production and an imported manure volume equivalent to a 500-cow dairy, the net 132 return to management and unpaid factors increased 388% compared to the seasonal dairy alone. Facility and structure costs increased 108%, manure handling and related labor costs increased 302%, but bedding costs decreased 67% and energy costs decreased 34%. Net purchased feed and bedding costs decreased 761% mainly because of the sale of cash crops; therefore AD on the seasonal farm was primarily paid for from the sales of cash crops. 5. Nitrogen, phosphorous and potassium were imported primarily through purchased feed and a small amount (28 kg/ha) of commercial N applied to corn at planting. The primary source of N was fixation by alfalfa and other legumes in the grass/ legume pasture. Nutrient exports were from milk, meat and feed sales, nutrients lost to the environment by volatilization, leaching, and runoff. The corn/alfalfa rotation on the confinement dairy led to an annual depletion of soil P (2.2 kg/ha-yr) and K (7.1 kg/ha-yr). The seasonal pasture cropping system led to a build-up of P (9 kg/ha-yr) and k (41.9 kg/ha-yr) while the annual pasture led to a P build-up of 11.2 kg/ha-yr and K build-up of 14.6 kg/ha/yr. 6. The addition of an anaerobic digester on the confinement farm increased K depletion in the cropping system (from 7.1 to 17.8 kg/ha-yr) because a portion of the chopped straw bedding was separated and recycled, thereby reducing the amount of K imported in the purchased bedding. 7. There was 68% more N available on the annual pasture dairy and 61% more N available on the seasonal pasture dairy than was available on the confinement farm. Of the N imported to the confinement dairy (195 kg/ha-yr), 39% was lost by volatilization, 6% by leaching and 4% by denitrification. Of the N imported to the seasonal dairy (326 kg/ha-yr) 51% was lost to volatilization, 16% to leaching and 12% to denitrification. The annual pasture imported 342 kg/ha-yr and lost 46% to volatilization, 6% to leaching and 4% to denitrification. 133 8. There was little difference in nitrogen, phosphorus, potassium and carbon loss to the environment from anaerobic digestion. 9. On the seasonal pasture, compared to confinement, emissions of ammonia increased 117%, nitrous oxide 92%, methane 20% and biogenic carbon dioxide 16%. Emissions of hydrogen sulfide decreased 19% and combustion CO2 decreased 16%. 10. On the annual pasture, compared to confinement, ammonia emissions increased 105% and nitrous oxide 30%. Hydrogen sulfide decreased 88%, combustion CO2 decreased 32%, methane decreased 6% and biogenic carbon dioxide decreased 5%. 11. On the seasonal pasture, compared to confinement, the water use footprint increased 5% and in the annual pasture increased 19% because of an increase in purchased feed and an increase in number of cows. 12. On the seasonal pasture, compared to confinement, the energy footprint decreased 14% and decreased 9% in the annual pasture due to a reduction in on-farm feed production, animal feeding and manure handling related to the shift from corn production to grazing land. 13. On the seasonal pasture, compared to confinement, carbon footprint increased 9% because animal and feed production emissions increased due to an increase in number of animals and forage intake. The annual pasture dairy had a 2% decrease in carbon footprint because of a decrease in manure emissions and fuel combustion. 14. On the seasonal pasture, compared to confinement, the reactive nitrogen footprint increased 108% and the annual pasture reactive nitrogen footprint increased 86% because of an increase in production of resource inputs and ammonia emission. In addition, the seasonal pasture had a higher nitrogen footprint because of an increase of 325% on nitrate leaching. 134 15. When the land base on the seasonal pasture was increased with manure imported to maintain the digester the water footprint increased 44%, reactive nitrogen footprint increased 63%, the energy footprint 11% and the carbon footprint 192% compared to the seasonal dairy alone. 135 CHAPTER 6: SUGGESTIONS FOR FUTURE RESEARCH Since one of the limitations was to integrate an anaerobic digester into a small-scale farm with imported manure, is important to validate the procedure performed for this study using IFSM model by comparing results with actual farm records. Pasture-based dairy farms are gaining popularity, because of the economic benefits. There is a need to collect more information related to confinement-winter/pasture-summer and pasture-based systems, which could be representative information for performing similar researches. Currently small and medium scale dairy farms are the most common type of dairy (74% has less than 100 cows) in the United States and, anaerobic digestion and methane recovery is gaining importance because of the environmental and economic benefits. There is a need for further research to make this technology more available and cost effective for small-scale dairy farms. 136 APPENDICES 137 APPENDIX A: DATA COLLECTED FROM FARM VISITS ON CONVENTIONAL CONFINEMENT DAIRIES 138 Table A. 1. Land information collected from confinement farm Unit Farm Other sources Total land ac 420 Owned land ac 88 452 (TelFarm, 2011) Rented land ac 332 280 (TelFarm, 2007) Total crop area ac 420 736 (TelFarm, 2011) Alfalfa area ac 160 Grass area ac 0 Corn area ac 230 Small grain area ac 30 Soybeans area ac 0 Grazing area ac 0 Table A. 2. Crop information collected from confinement farm Unit Farm Other sources Alfalfa Stand life for alfalfa years 4 Manure applied to alfalfa % 0 7 (MSU Extension, 2004) Corn Plant population of corn plant/ac 25,000-30,000 (IFSM Default) Relative maturity index of corn days 101 Manure applied to corn % 70 3 (MSU Extension, 2004) Irrigation for crops or grazing area in 0 Table A. 3. Animal information collected from confinement farm Unit Farm Animal type Mature cow body weight lb Animal average milk fat content % Animal fiber intake capacity Target milk production lb/cow/ year 29,200 Herd First Lactation animals % Calving strategy Lactating cows 131 Young stock over one year 136 Young stock under one year 50 Labor for milking and animal handling min/cow/day - 139 Other sources Small Holstein 1369 (IFSM) 3.5 (IFSM) 1 (IFSM) 10,000-22,000 (IFSM) 25-40% (IFSM) - Table A. 4. Livestock expenses information collected from confinement farm Unit Farm Other sources Veterinary and medicine $/cow 100 118 (TelFarm,2011) Semen and breeding $/cow 15 54 (TelFarm,2011) Animal and milking supplies $/cow 166 (TelFarm,2011) Insurance of animals $/cow 11 78 (TelFarm,2011) Animal hauling $/cow 0 10 (TelFarm,2011) DHIA, registration, etc $/cow 40 (TelFarm,2011) Table A. 5. Animal feeding information collected from confinement farm Unit Farm Feeding method Grain Loader and mixer wagon Silage Loader and mixer wagon Hay Self-fed in hay feeder Ration Constituents Minimum dry hay in cow % of forage 0 ration Phosphorus feeding level % of NRC recommendation Protein feeding level % of NRC recommendation Relative forage to grain ratio High Crude protein supplement Soybean meal 48% Undegradable protein Distillers Grain Energy supplement Dry Corn 140 Other sources 33 (USDA, 2000) - Table A. 6. Animal facilities information collected from confinement farm Unit Farm [a] Milking center Type Structure cost Equipment cost $ $ Double 5 parlor 136,000 - $ Free Stall Barn, naturally ventilated 200,000 $ Bedded pack barn 50,000 [a] Cow housing Type Structure cost Heifer housing Type Structure cost [a] [a] Feed facility Type Commodity shed Structure cost $ [a] No information collected from other sources Table A. 7. Manure information collected from confinement farm Unit Farm Manure Characteristics Type % DM 12-14 Collection and Use Collection method Scraper with bucket loading Incorporation by tillage Delayed Average hauling distance mile 1.5 Field application method Broadcast spreading Manure Storage Type Top-loaded earthen basin Storage period Capacity Storage initial cost Bedding Type of bedding Amount of bedding Import/Export of manure Import Export Other sources - months ton $ 4150 - Top-loaded concrete tank (MI Gov., 2012) - lb/cow/day Saw dust 4 - - no no - 141 Table A. 8. Storage structures information collected from confinement farm Unit Farm [a] Storage 1 Type of storage Type of forage or grain stored Quantity Capacity Initial cost ton DM $ Sealed silo High quality forage (Haylage) 1 525 - ton DM Sealed silo High moisture grain 1 22,000 $ - ton DM $ Bunker silo Grain crop silage 1 1900 - [a] Storage 2 Type of storage Type of forage or grain stored Quantity Capacity Initial cost [a] Storage 3 Type of storage Type of forage or grain stored Quantity Capacity Initial cost [a] Storage 4 Type of storage Type of forage or grain stored Quantity Capacity ton DM Initial cost $ [a]No information collected from other sources 142 Pressed bag High quality forage (Haylage) 1 12,700 - APPENDIX B: DATA COLLECTED FROM FARM VISITS ON SEASONAL PASTURE AND PASTURE-BASED DAIRIES 143 Table B. 1. Land information collected from seasonal pasture and pasture-based farms Unit Farm 1 Farm 2 Farm 3 Farm 4 Other sources Total land ac 315 226 205 879 Owned land ac 245 120 140 844 379 (TelFarm, 2007) Rented land ac 70 106 65 35 237 (TelFarm, 2007) Total crop area ac 210 0 0 377 525 (TelFarm, 2007) Alfalfa area ac 120 66 60 131 Grass area ac 55 160 65 175 42 (TelFarm, 2007) Corn area ac 50 0 0 245 Small grain area ac 0 0 0 132 Soybeans area ac 0 0 0 0 Grazing area ac 55 226 128 206 - 144 Table B. 2. Crop information collected from seasonal pasture and pasture-based farms Unit Farm 1 Farm 2 Farm 3 Farm 4 Other sources Alfalfa Stand life for years 3 5 5 5 alfalfa Manure applied to % 10 0 0 34 7 (MSU Extension, 2004) alfalfa Grass Stand life for years 10 12 10 grass Initial Sward dry matter of lb/ac 1447 418 (IFSM Default) grass Initial Sward 70% 67% 70% 60% composition of % CS and CS and CS and CS and grass 30% L 33% L 30% L 40% L Manure applied to % 0 100 100 0 grass Corn Plant 25,000-30,000 (IFSM population of plant/ac 30,000 25,000 Default) corn Relative maturity index days 95 103 of corn Manure % 90 10 3 (MSU Extension, 2004) applied to corn [a] CS= Cool-season grass; L=Legume 145 Table B. 3. Animal information collected from seasonal pasture and pasture-based farms Unit Farm 1 Farm 2 Farm 3 Farm 4 Other sources Animal Characteristics New Small Small Small Animal type Zealand Small Holstein Holstein Holstein Holstein Friesian Mature cow body lb 1000 1000 1300 1369 (IFSM) weight Animal average % 3.5 3.5 (IFSM) milk fat content Animal fiber 0.8 1 (IFSM) intake capacity Target milk lb/cow/ 10,000-22,000 15,000 18,000 15,000 24,000 production year (IFSM) Herd First Lactation % 25-40% (IFSM) animals year Calving strategy round Lactating cows 100 90 100 120 Young stock over 40 30 35 one year Young stock 60 35 60 35 under one year Labor for milking min/ and animal cow/ 2.4 3.3 0.5 1 handling day Table B. 4.Livestock expenses information collected from seasonal pasture farms Unit Farm 1 Farm 2 Farm 3 Farm 4 Veterinary and $/cow 5 40 16 137 medicine Semen and breeding $/cow 20 no 16 40 Animal and milking supplies Insurance of animals Animal hauling $/cow - 130 - 130 $/cow no - - 0 $/cow 10 17 - 10 DHIA, registration, etc. $/cow - - - 77 146 and pasture-based Other sources 118 (TelFarm,2011) 54 (TelFarm,2011) 166 (TelFarm,2011) 78 (TelFarm,2011) 10 (TelFarm,2011) 40 (TelFarm,2011) Table B. 5. Animal feeding information collected from seasonal pasture and pasture-based farms Unit Farm 1 Farm 2 Farm 3 Farm 4 Other sources Feeding method Grain Loader Individual Individual Loader and and mixer computer computer mixer wagon feeder feeder wagon Silage No No No Loader and mixer wagon Hay Hand fed Self-fed in Self-fed in Self-fed in hay feeder hay feeder hay feeder Ration Constituents Minimum dry % of 80 0 33 hay in cow ration forage (USDA, 2000) Phosphorus % of 107 feeding level NRC recom. Protein feeding % of 109 level NRC recom. Relative forage High High High to grain ratio Crude protein No No Soybean Soybean supplement meal 48% meal 44% Undegradable Roasted Distillers Distillers protein soybean grain grain Energy Grain Grain Grain Grain supplement 147 Table B.6. Animal facilities information collected from seasonal pasture and pasture-based farms Unit Farm 1 Farm 2 Farm 3 Farm 4 [a] Milking center Type - Double 12 parlor Structure cost Equipment cost [a] Cow housing $ $ 60,000 30,000 Type - Structure cost $ [a] Heifer housing Type - Structure cost [a] Feed facility $ Pipeline system 57,000 42,000 Free stall barn, naturally ventilated 45,000 Bedded pack barn Free stall barn, naturally ventilated - - Bedded pack barn - - Automatic Robotic System, multi stall 600,000 400,000 Free stall barn, naturally ventilated 1,000,000 Bedded pack barn Calf hutches and dry lot - Short term storage of premix Structure cost $ 200 [a] No information collected from other sources Type Automatic Robotic System, multi stall 150,000 310,000 35,000 Free stall barn, naturally ventilated 300,000 Short term storage of premix - Short term storage of premix - Short term storage of premix 200,000 Table B. 7. Manure information collected from seasonal pasture and pasture-based farms Other Unit Farm 1 Farm 2 Farm 3 Farm 4 sources Manure Characteristics Type % DM 12-14 12-14 12-14 12-14 10 Dry matter % (ASABE, content 2013a) 3.8 Nitrogen % DM (ASABE, content 2013a) Organic 70 % total nitrogen (ASABE, N content 2013a) 148 Table B.7 (cont’d) 0.8 (ASABE, 2013a) 2.4 (ASABE, 2013a) Phosphorus content % DM - - - - Potassium content % DM - - - - Scraper with bucket loading Scraper with ramp loading Scraper with slurry pump Scraper with bucket loading - No No No No - 2 1 1 9 - Broadcast spreading Broadcast spreading Broadcast spreading Broadcast spreading - Collection and Use Collection method - Incorporation by tillage Average hauling mile distance Field application method Manure Storage Type - Toploaded concrete tank Storage period months None Capacity ton 124 Storage initial $ 4000 cost Bedding Type of Sand bedding Amount of lb/cow/ 3 bedding day Import/Export of manure Import No Export No Toploaded concrete tank Bottomloaded tank or basin Toploaded concrete tank 1 357 3 309 6 3000 Toploaded concrete tank (MI Gov., 2012) - 15000 - 103000 - Straw Saw dust Chopped straw - 18 0.60 3 - No No No No No 25% - 149 Table B. 8. Storage structures information collected from seasonal pasture and pasture-based Unit Farm 1 Farm 2 Farm 3 Farm 4 [a] Storage 1 Type of storage - Quantity Capacity Initial cost ton DM $ Sealed silo High quality forage (Dry corn) Type of forage or grain stored Sealed silo Sealed silo 2 Stave silo High moisture grain 1 Grain for milk cows 4 432 12 203 76 7,000 1,100 42,000 - - Bale - hay - Pressed bag Low and high quality forage - 0.3/bale - 70 - 40/bale - 20 - 500 - - - Sealed silo Grain for calves - 1 - Bunker silo Grain crop silage (corn and alfalfa) 1 for corn silage and 3 for alfalfa - 8 - 270 - 100 - 55,625 - 12.5 - 206 - - Inside a shed - - Dry hay - - 1 - - 300 - - 50,000 - - 167 Grain crop silage (Dry grain) 1 [a] Storage 2 Type of storage Type of forage or grain stored ton Capacity DM Initial cost $ $/ ton Annual cost DM [a] Storage 3 Type of storage Type of forage or grain stored Quantity - Capacity Initial cost Initial cost ton DM $ $/ton DM - [a] Storage 4 Type of storage Type of forage or grain stored Quantity ton Capacity DM Initial cost $ $/ton Initial cost DM [a]No information collected from other sources 150 Table B. 9. Economic information collected from seasonal pasture and pasture-based farms Unit Farm 1 Farm 2 Farm 3 Farm 4 Other sources General rates Diesel fuel $/gal 3.68(U.S Energy, 2013) 0.13 (MI Public Electricity $/KWh Service, 2012) $/pt/ 1.6 (MSU custom Grain drying ton machine, 2013) DM Labor wage $/h 30 11.3 (MI AEWR, 2013) Land rental $/acre 70 50.98 (TelFarm, 2011) Property tax % 0 2.5 (IFSM default) Fertilizer prices 0.53 (Purdue Extension, N $/lb 0.61 2011) P $/lb 1.68 0.56 (Purdue Ext.,2011) K $/lb 0.59 0.47 (Purdue Ext.,2011) Lime $/ton 0.01 (Purdue Ext.,2011) Annual seed and chemicals 84 (Iowa State New forage stand $/acre 200 200 200 133 University, 2012) Established forage $/acre 0 0 0 7 stand 223 Corn land $/acre 200 100 (NASS,2010) Oats land $/acre 104.39 Soybean land $/acre 58 (NASS,2010) Additional for corn following $/acre 5 corn rotation Buying prices Soybean meal $/ ton 184 365 (MSU, 2013) 44% DM $/ ton Distillers grain 150 (IFSM, 2012) DM $/ ton Corn grain 376 145(USDA, 2013) DM $/ ton Hay 500 320 180 (USDA, 2013) DM Fat $/ ton 200 184 Minerals / $/ ton 2,345 200 184 vitamins 151 Table B.9 (cont’d) Bedding material $/ ton Custom operations 6 0 170 100 - No No No No - Table B. 10. Grazing information collected from seasonal pasture and pasture-based farms Unit Farm 1 Farm 2 Farm 3 Farm 4 Other sources ac 55 226 128 206 1 ac/cow* (NRCS) Grazing area Grazing management costs Investment in $29/ac* (Iowa State $ 10,000 12,600 1,600 14,500 perimeter fence U, 2012) Investment in $17/ac* (Iowa State $ 2,000 1,400 8,000 temporary fence U, 2012) Investment in watering $ no 2,500 1,770 15,000 $25/ac* (NRCS) system Added annual cost of $/ac 54.5 82 135 10 seed and chemical Grazing strategy Labor for grazing h/ 10 10 10 6 management week Types of animals all all all all grazed Time on pasture h 22 22 22 22 * The cost of perimeter fence is $0.89 /ft and temporary fence is $0.2/ft(Iowa State Extension, 2012). To convert the cost per feet to cost per acre it was assumed each paddock area is 3 ac (from where is obtained the perimeter of all paddocks). Total number of paddocks were calculated based equations 1,2 and 3 and data from Table B.11. *Watering system were calculated with equations 4, 5 and 6, and based on data from Table B.12. (1) (2) Paddocks acres* Number of paddocks (3) 152 Table B. 11. Data for calculations for fence investments Data for calculations for fence investments Data used - Forage species for legume A: Height of cool season grass to start grazing (in) Recommended by NRCS (Purdue Extension AY-328) 70% of Orchadgrass, Tall fescue, perennial ryegrass 30 % of white clover 6-8 Height of legume to start grazing (in) 6-10 7 Rest period for cool season grass (days) Rest period for legume (days) Estimated dry matter yield of cool season grass mix (lb/ac/in) Daily forage dry matter intake for lactating dairy cow (%) Grazing efficiency for 8 paddock system (%) Paddock acres Animal weight 30-45 24-32 200-300 30 30 250 3-4 3 60% - 60 3 1000 Number of animals per paddock - 25 Forage species of cool season grass 7 (4) (5) (6) 153 Table B. 12. Data for calculations for investment in watering system Investment in Watering system (NRCS, MSU Extension ) Recommended by NRCS Data used System Intensive Grazed Pastures Intensive Grazed Pastures Animals Dairy cow 175 Distance to water on paddock (ft) 600-900 700 Distance to water source (ft) 1200 Gallons of water for Dairy 15-25 25 (gallons/cow/day) Daily water consumption 4375 (gallons/day) Tank refill (h) 8 Tank refill rate (gallons/min) Maximum 10 9.1 first 40% of distance with 1Pipe size 1/4in and last 60% of distance with 1in pipe Pipe price Small tank price (305 gallons) Large tank price (5000 gallons) Price obtained from commercial store Price obtained from commercial store Price obtained from commercial store 154 1-1/4 in = $1.18/ft 1 in = $0.87/ft $2,80 $2,670 APPENDIX C: DATA SELECTED FOR THE FIVE REPRESENTATIVE DAIRY PRODUCTION SYSTEMS 155 Table C. 1. Representative farms Scenario Characteristics F1 Confinement F2 Confinement with AD F3 Seasonal 140 cows F4 Seasonal pasture with imported manure, cash crop and AD F5 Annual pasture-based F6 Confinement 500 cows Table C. 2. Land information selected for farms F1, F2, F3, F4, F5, F6 Unit F1 F2 F3 F4 F5 Total land ac 275 275 275 2000 275 Owned land ac 175 175 175 175 175 Rented land ac 100 100 100 1825 100 Total crop area ac 275 275 275 1875 0 Alfalfa area ac 90 90 25 25 100 Grass area ac 0 0 125 125 175 Corn area ac 185 185 125 925 0 Soybeans area ac 0 0 0 925 0 156 F6 1270 175 1095 1270 450 0 820 0 Table C. 3. Crop information for farms F1, F2, F3, F4, F5, F6 Unit F1 F2 F3, F4 Alfalfa Stand life year 4 4 4 Yield adjustment % 100 100 100 factor N application rate lb/ac 0 0 0 P application rate lb/ac 0 0 0 K application rate lb/ac 0 0 0 [a] % 0 0 0 Manure applied Corn Plant population Relative maturity index Yield adjustment factor N application rate, pre-planting N application rate, post-planting P application rate K application rate Manure applied Grass Stand life Initial Sward dry matter Initial Sward composition of Yield adjustment factor N application rate P application rate K application rate Manure applied [a] F5 F6 4 100 4 100 0 0 0 20 0 0 0 0 plant/ac days 28,000 100 28,000 100 28,000 100 - 28,000 100 % 100 100 100 - 100 lb/ac 0 0 0 - 0 lb/ac 25 25 25 - 25 lb/ac lb/ac % 0 0 100 0 0 100 0 0 100 - 0 0 100 years lb/ac - - 10 418 10 418 - % - - - - 70% CS and 30% [b] L 110 - % 70% CS and 30% [b] L 110 lb/ac lb/ac lb/ac % - - 0 0 0 0 0 0 0 80 0 0 - [a] The amount of manure applied is the percentage of the amount of manure collected on the milking center [b]CS =Cool-Season grass; L=Legume 157 Table C. 4. Grazing information for farms F3, F4 and F5 Unit F3, F4 Grazing area Spring ac 75 Summer ac 125 Fall ac 100 Grazing management costs Investment in perimeter fence $ 3,625 Investment in temporary fence $ 2,125 Investment in watering system $ 3,125 Added annual cost of seed and $/ac 30 chemical Grazing strategy Labor for grazing management h/week 10 Grazed forage yield adjustment % 120 factor Types of animals grazed All cows Time on pasture h Full days during grazing season 158 F5 100 175 150 5,075 2,975 4,375 30 10 120 All cows Full days during grazing season Table C. 5. Animal information for farms F1, F2, F3, F4, F5, F6 Unit F1 F2 F3, F4 Animal Characteristics Large Large Medium Animal type [a] Hols Hols Hols Mature cow lb 1600 1600 1300 body weight Animal average % 3.5 3.5 3.8 milk fat content Animal fiber 1 1 1 intake capacity Target milk lb/cow/ year 24,000 24,000 20,000 production Herd First Lactation % 35 35 25 animals Year Year Year Calving strategy round round round Lactating cows 100 100 142 Young stock 38 38 54 over one year Young stock 42 42 60 under one year Labor for milking and min/cow/day 5.25 5.25 3.0 handling Livestock Expenses Veterinary and $/cow 118 118 85 medicine Semen and $/cow 54 54 39 breeding Animal and $/cow 166 166 107 milking supplies Insurance of $/cow 78 78 78 animals Animal hauling $/cow 10 10 10 DHIA, $/cow 40 40 40 registration [a] Hols = Holstein 159 F5 F6 Small Hols Large Hols 1000 1600 4.2 3.5 1 1 16,000 24,000 30 35 Year round 160 Year round 500 61 190 67 210 3.0 5.25 101 118 46 54 143 166 78 78 10 10 40 40 Table C. 6. Animal feeding information for farms F1, F2, F3, F4, F5, F6 Unit F1, F2, F3, F4 F5, F6 Feeding method Loader and mixer Loader and mixer Grain wagon wagon Loader and mixer Loader and mixer Silage wagon wagon Hay - Bale grinder Ration Constituents Minimum dry hay in cow ration P feeding level Protein feeding level Relative forage: grain % forage % NRC recom. % NRC recom. - Crude protein supplement - Undegradable protein Energy supplement - Bale grinder 5 0 100 100 High Soybean meal 48% Distiller Grain Grain 100 100 High Soybean meal 48% Distiller Grain Grain Table C. 7. Animal facilities information for farms F1, F2, F3, F4, F5, F6 Unit F1, F2 F3, F4 F5 F6 Milking center Double 6 Double 6 Double 6 Double 12 Type parlor parlor parlor parlor Structure cost $ 182,000 182,000 137,000 274,000 Equipment cost $ 233,600 233,600 175,000 350,000 Cow housing Free Stall Free Stall Free Stall Barn, Barn, Barn, Type None naturally naturally naturally ventilated ventilated ventilated Structure cost $ 140,000 196,000 700,000 Heifer housing Calf Calf Calf Calf Type hutches hutches hutches hutches and dry lot and dry lot and dry lot and dry lot Structure cost $ 26,700 37,450 42,650 133,500 Feed facility Short term Short term Short term Short term Type storage storage storage storage premix premix premix premix Structure cost $ 4,500 6,300 7,200 22,500 160 Table C. 8. Manure information for farms F1, F2, F3, F4, F5, F6 Unit F1 F2 F3, F4 Manure Characteristics Type % DM 12-14 12-14 12-14 Dry matter content % 10 10 10 Nitrogen content % DM 3.8 3.8 3.8 Organic nitrogen content % total N 70 70 70 Phosphorus content % DM 0.8 0.8 0.8 Potassium content % DM 2.4 2.4 2.4 Collection and Use Scraper Scraper Scraper with with with Collection method slurry slurry slurry pump pump pump Within Within Within Incorporation by tillage 2 days 2 days 2 days Average hauling distance mile 0.5 0.5 0.75 Manure Storage TopTopToploaded loaded loaded Type lined lined lined earthen earthen earthen basin basin basin Storage period months 6 6 6 Capacity ton 1,882 1,882 1,699 Storage initial cost $ 45,224 45,224 44,322 Bedding Chop Chop Chop Type of bedding Straw Straw Straw lb/cow/ [a] Amount of bedding 3 1 1 day Import/Export of manure Import ton 0 0 14,200 Export ton 0 0 0 [a]Farm F3 has an amount of bedding of 3 lb/cow/day 161 F5 F6 12-14 10 3.8 70 0.8 2.4 12-14 10 3.8 70 0.8 2.4 Scraper with bucket loading Scraper with slurry pump Within 2 days 1.0 No 0.5 Slab with buckwall 0 0 0 Toploaded lined earthen basin 6 9,227 81,223 None Chop Straw 0 3 0 0 0 0 Table C. 9. Storage structure information for farms F1, F2, F3, F4, F5, F6 Unit F1 F2 F3, F4 F5 Storage 1 Type of Bunker Bunker Bunker silo Bale storage silo silo Type of High High High High quality forage or quality quality quality forage grain stored forage forage forage ton Capacity 423 423 202 423 DM Initial cost $ 56,982 56,982 32,567 56,982 $/ ton Annual cost 2.0 2.0 2.0 2.0 DM Storage 2 Type of Bunker Bunker Bunker silo storage silo silo Type of Grain Grain Grain crop forage or crop crop silage grain stored silage silage ton Capacity 476 476 476 DM Initial cost $ 61,637 61,637 61,637 $/ ton Annual cost 2.0 2.0 2.0 DM Storage 3 Type of Stave silo Stave silo storage Type of High High forage or moisture moisture grain stored grain grain ton Capacity 191 191 DM Initial cost $ 38,910 38,910 Storage 4 Type of Inside a Inside a Inside a Inside a storage shed shed shed shed Type of forage or Dry hay Dry hay Dry hay Dry hay grain stored ton Capacity 120 120 120 120 DM Initial cost $ 25,960 25,960 25,960 25,960 Annual grain $/ ton 12 12 12 12 DM storage 162 F6 Bunker silo High quality forage 2028 198,470 2.0 Bunker silo Grain crop silage 2,168 204,508 2.0 Sealed silo High moisture grain 979 90,547 Inside a shed Dry hay 200 50,000 12 Table C. 10. Machine information for farms F1, F2, F3 and F4 F1,F2 Operation Number Machine Tractor Number type/size size Harvest/ Feeding Mowing 1 Raking 1 Baling 1 Bale wrapping 0 Forage chopping 1 Grain harvesting 1 Feed mixing 1 Silo filling 1 Tillage / Planting Manure handling 1 Plowing 1 Field cultivation 1 Row crop planting 1 Drill seeding 1 Spraying 1 Mower conditioner 14 ft Tandem rake 18 ft Small round baler 0 134 hp 1 47 hp 1 108 hp 1 0 1 Medium forage harvester Medium corn combine 8 row Large mixer 13 ton Forage blower/ bunker packing 134 hp 1 none 2 87 hp 1 108 hp 1 Medium slurry tank spreader Coulterchisel plow 12 ft Seedbed conditioner 19 ft Corn planter 8 row Grain drill 12 ft Sprayer 50 ft 134 hp 1 134 hp 1 134 hp 1 108 hp 1 47 hp 1 87 hp 1 [a]Farm F3 uses 1 medium corn combine of 8 row. 163 [a] F3, F4 Machine type/size Tractor size Mower conditioner 9 ft Single rake 9 ft Medium round baler Large round bale wrapper Medium forage harvester Medium corn combine 8 row Large mixer 13 ton Forage blower/ bunker packing 87 hp Medium slurry tank spreader Coulterchisel plow 12 ft Seedbed conditioner 19 ft Corn planter 8 row Grain drill 12 ft Sprayer 50 ft 134 hp 47 hp 108 hp 87 hp 134 hp none 87 hp 108 hp 134 hp 134 hp 108 hp 47 hp 87 hp Table C. 11. Machine information for farms F5 and F6 F5 F6 Operation Number Machine Tractor Number Machine type/size size type/size Harvest/ Feeding Mowing 1 Raking 1 Baling 1 Bale wrapping 1 Forage chopping [a] Tractor size 108 hp 2 SP mower conditioner 16ft none 87 hp 1 0 0 108 hp 2 87 hp 1 0 1 Grain harvesting 0 0 0 1 Feed mixing 1 Large mixer 13 ton 87 hp 2 Windrow merger 32ft Medium round baler Large SP forage harvester Medium corn combine 8 row Large mixer 13 ton Forage blower/ bunker packing 134hp 0 Disc mower conditioner 10ft Tandem rake 18 ft Medium round baler Large round bale wrapper 0 Silo filling 2 Tillage / Planting Manure handling 1 Plowing 1 Field cultivation 1 108 hp 2 134 hp 1 87hp 1 Row crop planting 0 Small V- tank spreader Coulter-chisel plow 12 ft Seedbed conditioner 15ft 0 0 1 Drill seeding 1 Grain drill 8ft 47 hp Spraying 0 0 0 [a]SP = self-propelled 164 108 hp none none 108hp 220hp Large slurry tank 220 hp spreader Coulter-chisel 220hp plow 20ft Seedbed 134 hp conditioner 19 ft 108 hp 1 Corn planter 8 row Grain drill 16ft 1 Sprayer 50 ft 108hp 108hp Table C. 12. Miscellaneous information for farms F1, F2, F3 and F4 F1,F2 Operation Number Machine Miles Number type/size transport Transport 3 47 hp 3 tractors Medium Feed/ Manure 1 skid-steer 1 loader loader Round bale 1 87 hp 1 loader Manure pump/ 108 hp agitator Auxiliary No manure pump Initial machine shed $25,000 cost Custom operations - Grain Harvest - - F3, F4 Machine type/size Miles transport 47 hp - Medium skid-steer loader - 87 hp - 108 hp - No - $25,000 Grain Harvest / Grain crop planting - Transport of feed Round bale wagons Round bale Hay crop 2 Dump wagons 0.5 2 wagons and silage wrappers Grain crop Dump 2 Dump wagons 0.5 2 silage wagons Grain Grain 3 Grain wagons 0.5 3 wagons [a]Farm F3 uses 0.75 miles of hauling distance for grain crop silage and grain Hay 1 Round bale wagons 0.5 165 1 0.5 0.5 [a] 0.5 [a] 0.5 Table C. 13. Miscellaneous information for farms F5 and F6 F5 Operation Number Machine Miles Number type/size transport Transport 2 47 hp 5 tractors Feed/ Manure Small skid1 2 loader steer loader Round bale 1 108hp 1 loader Manure pump/ No agitator Auxiliary No manure pump Initial machine shed $20,000 cost Forage crop Custom tillage/plant operations ing Transport of feed Round bale Hay 1 0.5 2 wagons Round bale Hay crop 2 wagons and 0.5 6 silage wrappers Grain crop 2 Dump wagons 0.5 6 silage Grain 2 Grain wagons 0.5 3 166 F6 Machine type/size Miles transport 67 hp - Large skidsteer loader 67 hp - 134hp - No - $50,000 Grain Harvest - Round bale 0.5 wagons Dump wagons Dump wagons Grain wagons 1.0 1.0 1.0 Table C. 14. Tillage and planting information for farms F1, F2, F3, F4, F5, F6 Operation Start date Alfalfa Operation 1 Operation 2 Operation 3 Operation 4 Corn Operation 1 Operation 2 Operation 3 Operation 4 Operation 5 Grass Operation 1 Operation 2 Operation 3 Operation 4 Soybean Operation 1 Operation 2 Operation 3 Operation 4 Moldboard /Chisel plow Field cultivator/ conditioner Field cultivator/ conditioner Alfalfa seeding 15-Oct 10-Apr 10-Apr 15-Apr Moldboard /Chisel plow Field cultivator/ conditioner Field cultivator/ conditioner Corn planting Sprayer 10-Sept 10-Apr 25-Apr 01-May 10- May No operation Field cultivator/ conditioner Field cultivator/ conditioner Grass seeding 15-Apr 20-Apr 20-Apr Field cultivator/ conditioner Field cultivator/ conditioner Soybean planting Sprayer 10- Apr 25- Apr 01- May 10- May Max simultaneous operations: 2 Time available for tillage and planting: 8h/day Table C. 15. Corn harvest information for farms F1, F2, F3, F4, F5, F6 Starting date Corn Silage 1-Sep High moisture corn Dried corn 1-Oct 21-Oct Harvest detail Maximum silage moisture content 68% Corn silage cutting high 6 in Corn silage processing High moisture corn type Rolled with greater chop length Grain w/ little or no cob and husk 167 Table C. 16. Alfalfa harvest information for farms F1 and F2 Harvest 1 Harvest 2 Mechanical Mechanical Drying Treatment conditioning, conditioning, wide swath wide swath Harvest 3 Mechanical conditioning, narrow swath Harvest 4 Mechanical conditioning, narrow swath Tedding treatment No No No No Raking treatment Before harvest Before harvest Before harvest Before harvest Harvest type Wilted silage harvest by chopping Hay harvest by baling Wilted silage harvest by chopping Wilted silage harvest by chopping 0 0 0 0 68 20 68 68 42 42 42 42 Chemical conditioning application rate (g/ac) Maximum moisture content at harvest (%) Critical NDF for high quality storage (%) Schedule for Alfalfa 4 cuttings- Bud first 2 cuttings, early flower last 2 168 Table C. 17. Alfalfa and grass harvest information for farms F3 and F4, F5 Alfalfa Harvest 1 Harvest 2 Harvest 3 Harvest 4 Mechanical Mechanical Mechanical Mechanical Drying conditioning, conditioning, conditioning, conditioning, Treatment wide swath wide swath narrow swath narrow swath Tedding treatment Raking treatment Harvest type Chemical conditioning application rate (g/ac) Maximum moisture content at harvest (%) Critical NDF for high quality storage (%) Schedule for Alfalfa Grass Harvest 1 Mechanical conditioning, wide swath No No No No No Before harvest Round bailing for silage Before harvest Before harvest Round bailing for silage Before harvest Round bailing for silage Before harvest Round bailing for silage 0 0 0 0 0 60 20 60 60 60 42 42 42 42 42 Hay harvest by baling 4 cuttings- Bud first 2 cuttings, early flower last 2 169 1 cuttingearly head Table C. 18. Alfalfa harvest information for farm F6 Harvest 1 Harvest 2 Mechanical Mechanical Drying Treatment conditioning, conditioning, wide swath wide swath Harvest 3 Mechanical conditioning, narrow swath Harvest 4 Mechanical conditioning, narrow swath Tedding treatment No No No No Raking treatment Before harvest Before harvest Before harvest Before harvest Harvest type Wilted silage harvest by chopping Wilted silage harvest by chopping Wilted silage harvest by chopping Wilted silage harvest by chopping 0 0 0 0 68 65 68 68 42 42 42 42 Chemical conditioning application rate (g/ac) Maximum moisture content at harvest (%) Critical NDF for high quality storage (%) Schedule for Alfalfa 4 cuttings- Bud first 2 cuttings, early flower last 2 170 Table C. 19. Hauling costs for imported manure in seasonal pasture system (F4) Pumping and trucking from farm to AD Custom work Labor hours (h) 301 Custom cost ($/h) 90 Total custom cost ($) 27,090 Hauling from AD to field Tractor 100 kW List price ($) 108,000 Purchase price ($) 97,000 Labor hours per tractor (h) 148 Machinery rate ($/h) 25.36 Fuel and lubrication rate ($/h) 26.83 Total tractor cost ($) 15,448 Spreader List price ($) 44,000 Purchase price ($) 39,600 Machinery rate ($/h) 43.26 Labor hours per spreader (h) 148 Total spreader cost ($) 12,805 Labor Hours 296 Labor rate ($/h) 16.13 Total labor cost ($) 4,775 33,028 Total cost ($) 171 APPENDIX D: RESULTS FROM IFSM OF THE FIVE REPRESENTATIVE DAIRY PRODUCTION SYSTEMS 172 Table D. 1. Development of seasonal pasture farm with 142 medium-frame Holsteins, cash crop, imported manure and AD Seasonal Confine Seasonal Seasonal Confine Confine Seasonal Seasonal ADCC/ CC/Import/ AD[a] [a] [b] [b] [c] [d] AD AD AD Unit Confine Seasonal Import Mean Mean % Mean Mean % Mean Mean Nutrients available, used, and lost to the environment Nitrogen lost by leaching lb/ac 12.3 10.9 -11% 45.8 41.7 -9% 11.6 10.3 Nitrogen lost by denitrification lb/ac 8.7 7.3 -16% 36.2 32.9 -9% 7.2 6.0 Potassium loss through runoff lb/ac 5.7 5.2 -9% 8.6 8.2 -5% 2.9 2.6 Soil potassium depletion lb/ac 3 13.1 337% 0 0 0% 0 0.0 Crop removal over that available on farm % 90 99 10% 76 80 5% 76 80.0 Annual manure production and handling cost Manure handled ton 17193 16897 -2% 3187 3150 -1% 3179 16897 Manure applied to corn land ton 17193 16897 -2% 3187 3150 -1% 3179 16897 Machinery cost $ 52790 48297 -9% 18763 16315 -13% 29854 25361 Fuel and electric cost $ 10777 9458 -12% 1771 1543 -13% 8154 6835 Storage cost $ 7081 99463 1305% 3864 19961 417% 3864 96246 Labor cost $ 21004 32078 53% 4115 20162 390% 4775 15849 Annual crop production and feeding costs and the net return over those costs Equipment cost $ 340664 336864 -1% 95937 95225 -1% 94772.6 92017 Facilities cost $ 243555 335916 38% 84918 101014 19% 85031 177392 Energy cost $ 121078 39560 -67% 20196 7340 -64% 41613 13292 Land rental cost $ 57707 57707 0% 5270 5270 0% 96178 96178 Return to $ 705603 714655 1% 86442 73227 -15% 472633 420348 173 Table D.1 (cont’d) management and unpaid factors Annual emissions Ammonia Housing facility lb Manure storage lb Methane Manure storage lb Biogenic Carbon Dioxide Manure storage lb Combustion Carbon Dioxide lb Environmental footprints Water Use Production of purchased feed and inputs ton Not allocated to milk production ton Water footprint with lb/lb rainfall FPCM Water footprint lb/lb without rainfall FPCM Reactive Nitrogen Loss Ammonia emission lb Nitrate leaching lb Nitrous oxide emission lb Fuel combustion lb 48889 22343 47934 23935 -2% 7% 14921 10020 14959 11119 0.3% 11% 14950 10228 14988 11350 122905 91039 -26% 15573 15724 1% 15530 15681 463194 2629466 468% 59301 469126 691% 59156 467979 474590 414113 -13% 65780 52019 -21% 56737 44868 684185 490677 -28% 359740 321983 -10% 362208 362208 -644537 -615283 -5% -176419 -172232 -2% -226226 -220857 568 538 -5% 630 603 -4% 946 905 95 65 -32% 195 169 -13% 197 171 96413 15641 99351 13869 3% -11% 40650 12591 42884 11462 5% -9% 60511 23291 63836 21203 3459 1522 3327 1330 -4% -13% 1310 207 1280 164 -2% -21% 2442 812 2386 710 174 Table D.1 (cont’d) emissions Reactive nitrogen footprint Energy Use Manure handling Production of resource inputs Not allocated to milk production lb/cwt FPCM 0.92 0.92 0% 1.85 1.88 2% 2.93 3.0 MBtu 389961 342256 -12% 64096 55845 -13% 291200 244107 MBtu 8591305 5410426 -37% 2046323 1545287 -24% 3098770 2355065 MBtu -2127975 -1585832 -25% -505640 -442520 -12% -616518 -542536 MBtu/lb Energy footprint FPCM 0.94 0.66 -30% 0.82 0.62 -24% 1.17 0.89 Greenhouse Gas Emissions (CO2e) Manure emissions lb 4372728 3539654 -19% 795756 796061 0.04% 844711 845035 Emission during feed production lb 403339 375736 -7% 213438 203133 -5% 153939 146507 Net biogenic carbon dioxide emission lb -4031126 -3942799 -2% -930755 -931179 0.05% 3226541 3228011 Fuel combustion emissions lb 474590 414113 -13% 65780 52019 -21% 56737 44868 Production of resource inputs lb 2170564 1442038 -34% 579850 463668 -20% 740470 592105 Not allocated to milk production lb -2134571 -1884921 -12% -538999 -524117 -3% -555418 -540083 Carbon footprint lb/lb without biogenic CO2 FPCM 0.97 0.84 -13% 1.04 0.99 -5% 1.09 1.0 Carbon footprint with lb/lb biogenic CO2 FPCM 0.66 0.53 -20% 0.72 0.68 -6% 2.18 2.1 [a] Confinement farm with 500 large-frame Holsteins, [b] Seasonal pasture farm with 140 medium-frame Holsteins, [c] Seasonal pasture farm with 140 medium-frame Holsteins, with cash crop and imported manure, [d]Target farm: Seasonal pasture farm with 140 medium-frame Holsteins, with cash crop, imported manure and AD. 175 Table D. 2. Average postharvest yield for crops of F1, F2, F3, F4, F5 Unit F1 F2 F3 Alfalfa yield ton DM/ac 5.26 5.26 5.19 Corn silage yield ton DM/ac 5.69 5.64 5.77 HM Corn yield ton DM/ac 2.73 2.72 0 Dry Corn yield ton DM/ac 2.88 2.86 2.67 Grass yield ton DM/ac 1.69 Soybean yield ton DM/ac - F4 5.18 6.15 0 2.76 1.84 1.02 F5 5.2 0 0 0 1.71 0 Table D. 3. Annual feed production and utilization of F1, F2, F3, F4, F5 (Average) Unit F1 F2 F3 High-quality hay production ton DM 51 51 18 Low-quality hay production ton DM 31 31 5 High-quality silage production ton DM 257 257 106 Grain crop silage production ton DM 412 412 409 High moisture grain production ton DM 166 166 0 Dry grain production ton DM 90 87 110 Cash crop grain sold ton DM 0 0 0 Grazed foraged consumed ton DM 0 0 320 Forage sold ton DM 45 48 11 Forage purchased ton DM 0 0 0 Grain sold ton DM 20 17 41 Grain purchased ton DM 0 0 0 Soybean meal 48% purchased ton DM 18 19 277 Distillers grain purchased ton DM 133 135 155 Mineral and vitamin mix purchased ton DM 8 8 7 Milk production lb/cow 23731 23745 19276 Fat and protein corrected milk production lb/cow 21908 21921 18683 176 F4 17 5 111 413 0 3185 939 337 48 0 2248 0 281 163 7 19268 18676 F5 62 27 377 0 0 0 0 310 45 0 0 126 225 150 6 14594 15042 Table D. 4. Nutrients available, use and lost to the environment of F1, F2, F3, F4, F5 (Average) Unit F1 F2 F3 Nitrogen imported to farm lb/ac 174 174 291 Nitrogen exported from farm lb/ac 74.4 74.6 70.5 Nitrogen available on farm lb/ac 266 262 427.1 Nitrogen lost by volatilization lb/ac 68.1 69.9 147.8 Nitrogen lost by leaching lb/ac 10.8 9.9 45.8 Nitrogen lost by denitrification lb/ac 7.2 6.4 36.2 Average nitrogen concentration in leachate ppm 8.8 8.1 37.7 N crop removal over that available % 60 61 46 Phosphorous imported to farm lb/ac 10.5 10.3 20.4 Phosphorous exported from farm lb/ac 12.2 12.2 12.2 Phosphorous available on farm lb/ac 17.2 17.2 27.8 Phosphorous loss in runoff and leachate lb/ac 0.3 0.3 0.2 Soil phosphorous build up lb/ac 0 0 8 Soil phosphorous depletion lb/ac 2.0 2.2 0 P crop removal over that available % 115 117 76 Potassium imported to farm lb/ac 23.1 13.5 64.6 Potassium exported from farm lb/ac 24.6 24.6 18.5 Potassium available on farm lb/ac 96.5 86.8 172.4 Potassium loss through runoff lb/ac 4.8 4.3 8.6 Soil potassium build up lb/ac 0 0 37.4 Soil potassium depletion lb/ac 6.3 15.9 0 K crop removal over that available % 101 112 76 Carbon imported to farm lb/ac 6711 6557 5953 Carbon exported from farm lb/ac 998 995 929 Carbon loss as carbon dioxide lb/ac 5525 5391 4800 Carbon loss as methane lb/ac 186 169 223 Carbon loss through runoff lb/ac 1.2 1.2 1.2 177 F4 189 110 209 31.1 10.3 6.0 8.1 60 14.2 14.2 15 0.5 0 0.24 105 36.6 28.1 52.8 2.6 9.1 0 80 9388 1478 7902 28.1 1.4 F5 305.2 67.5 446.4 139.9 17.3 10.9 12.2 46 20 9.9 26.4 0 10 0 64 46.2 24.5 174.2 8.7 13 0 83 7984 789 7019 175 0.3 Table D. 5. Annual manure production, nutrient availability and handling cost of F1, F2, F3, F4, F5 (Average) Unit F1 F2 F3 F4 Manure handled ton 3478 3419 3187 16897 Manure applied to alfalfa land ton 0 0 0 0 Manure applied to grass land ton 0 0 0 0 Manure applied to corn land ton 3478 3419 3187 16897 Manure nitrogen over crop requirement % 51 48 109 58 Manure phosphorous over crop requirement % 89 88 136 99 Manure potassium over crop requirement % 101 90 135 127 Machinery cost $ 16468 14097 18762 25360 Fuel and electric cost $ 1947 1677 1771 6836 Storage cost $ 3943 24062 3864 96246 Labor cost $ 4561 20473 4114 15848 Bedding cost $ 8306 2768 8084 2695 Total manure handling cost $ 35226 63078 36596 146984 Total cost per mature animal $/cow 352 631 258 1035 178 F5 2865 573 2292 0 101 163 125 8562 1790 0 5617 0 15969 100 Table D. 6. Annual crop production, feeding costs and net return over those costs of F1, F2, F3, F4, F5 (Average) Unit F1 F2 F3 F4 F5 Equipment cost $ 85551 87070 80469 164334 45092 Fuel and electric cost $ 9709 9697 6998 17583 6108 Feed and machinery facilities cost $ 21983 21993 15865 15978 10866 Labor cost $ 17867 17839 18379 28084 18702 Seed, fertilizer and chemical cost $ 51111 51112 38949 340373 17128 Grain drying and roasting cost $ 559 522 654 13049 0 Land rental $ 5270 5270 5270 96178 5270 Purchased feed cost $ 38609 39015 130124 129987 128774 Income from feed sales $ 25125 24369 17234 931877 7901 Net feed cost $ 205534 208148 279474 -128050 224037 Net cost per unit of milk $/cwt 8.66 8.77 10.21 9.59 Net cost as portion of milk income % 45.6 46.1 53.8 50.5 Income from milk sales Net return over feed costs Net return per cow $ $ $/cow 450900 245366 2454 179 451160 243011 2430 520062 240588 1694 - 443650 219613 1373 Table D. 7. Annual production costs and net return to management of F1, F2, F3, F4, F5 (Average) Unit F1 F2 F3 Equipment cost $ 98926 98090 95937 Facilities cost $ 84452 104581 85262 Energy cost $ 21871 5348 20196 Labor cost $ 73943 89828 64294 Custom operation cost $ 3093 3078 3295 Seed, fertilizer and chemical cost $ 51111 51112 38949 Land rental cost $ 5270 5270 5270 Net purchased feed and bedding cost $ 21791 17414 120973 Animal purchase and livestock expense $ 46600 46600 50978 Milk hauling and marketing fees $ 23730 23744 27370 Property tax $ 5173 5173 5214 F4 92017 177623 13293 81912 97677 340373 96178 -799143 50978 27359 5214 F5 51273 57599 15998 71418 2380 17128 5270 120873 66880 23348 3727 Income from milk sales Income from animal sales $ $ 450900 61655 451160 61655 520062 83810 519862 83810 443650 80407 Return to management and unpaid factors $ 73594 62578 86133 420192 88162 180 Table D. 8.Crop production costs and feed costs of F1, F2, F3, F4, F5 (Average) Unit F1 F2 Crop Production costs Hay $/ton DM 176 178 Hay crop silage $/ton DM 172 173 Grain crop silage $/ton DM 159 160 High-moisture grain $/ton DM 202 203 Dry grain $/ton DM 165 166 Grazed forage $/ton DM 0 0 Feed costs Hay $/ton DM 253 269 Hay crop silage $/ton DM 208 209 Grain crop silage $/ton DM 192 193 High-moisture grain $/ton DM 215 216 Dry grain $/ton DM 166 167 Grazed forage $/ton DM 0 0 181 F3 F4 F5 289 252 189 0 204 62.2 283 237 160 0 178 59 126 135 0 0 0 87 339 283 223 0 200 80 327 261 189 0 187 76 208 173 0 0 158 106 Table D. 9. Annual emissions of important gaseous compounds of F1, F2, F3, F4, F5 (Average) Unit F1 F2 F3 F4 F5 Ammonia Housing facility lb 9493 9288 14986 14918 33370 Manure storage lb 4784 5100 11351 10019 0 Field application lb 8499 9001 42083 15752 5087 Grazing lb 0 0 8822 8729 8313 Total farm lb 22776 23389 77242 49419 46771 Hydrogen Sulfide Housing facility lb 77 75 64 65 87 Manure storage lb 139 135 108 110 0 Field application lb 502 481 2124 406 0 Grazing lb 0 0 1 1 1 Total farm lb 717 690 2297 582 88 Methane Housing facility lb 43369 43307 44577 44306 42945 Manure storage lb 24833 18415 15679 15572 0 Field application lb 83 88 448 157 87 Grazing lb 0 0 22075 21885 21229 Total farm lb 68285 61810 82779 81920 64261 Nitrous Oxide Housing facility lb 450 437 825 747 716 Manure storage lb 324 314 592 535 0 Farmland lb 296 278 2244 776 671 Total farm lb 1070 1030 3661 2058 1387 Biogenic Carbon Dioxide Housing facility lb 1510026 1509904 1223542 1220864 1110190 Manure storage lb 93567 531874 467938 0 59298 Assimilated in feed lb -2409483 -2830159 -2752647 1618090 -2355195 Grazing animal lb 0 0 538066 480428 538938 Net emission lb -805891 -788382 -930869 3844958 -764576 78598 66542 44870 Combustion Carbon Dioxide lb 65779 53068 182 Table D. 10. Table of environmental footprints of water, nitrogen, energy and carbon for F1, F2, F3, F4, F5 (Average) Unit F1 F2 F3 F4 Water Use Feed production, rainfall ton 645706 645876 645670 1111121 Drinking ton 3098 3098 4622 4613 Animal cooling ton 252 252 357 357 Parlor and equipment cleaning ton 1006 1006 1428 1428 Production of purchased feed and inputs ton 141444 102164 359683 362089 Not allocated to milk production ton -134981 -129020 -176406 -220842 Water footprint with rainfall lb/lb FPCM* 600 569 630 905 Water footprint without rainfall lb/lb FPCM 99 68 195 170 Reactive Nitrogen Loss Ammonia emission lb 18730 19235 40641 63836 Nitrate leaching lb 2961 2732 12588 21201 Nitrous oxide emission lb 681 656 1310 2386 Fuel combustion emissions lb 260 220 207 710 Production of resource inputs lb 945 776 2320 2140 Not allocated to milk production lb -4024 -4028 -8133 -11703 Reactive nitrogen footprint lb/cwt FPCM 0.89 0.89 1.85 3 Energy Use Feed production MBtu 204712 204588 133990 181040 Animal feeding MBtu 144480 144035 115955 114529 Manure handling MBtu 70449 60700 64088 244129 Milking and milk cooling MBtu 220185 147002 253959 170087 Animal housing ventilation and lighting MBtu 54782 54782 53622 53622 Production of resource inputs MBtu 1806638 1184093 2046170 2354809 Not allocated to milk production MBtu -427475 -320825 -505605 -542463 Energy footprint MBtu/lb FPCM 0.95 0.67 0.82 0.91 183 F5 644806 4384 403 1609 369910 -159448 716 244 38463 4771 883 168 2503 -6713 1.67 109217 105202 64762 216645 17147 1927342 -412267 0.84 Table D.1 (cont’d) Greenhouse Gas Emissions (CO2e) Animal emissions Manure emissions Emission during feed production Net biogenic carbon dioxide emission Fuel combustion emissions Production of resource inputs Not allocated to milk production Carbon footprint without biogenic CO2 lb lb lb lb lb lb lb lb/lb FPCM 1061739 875962 78141 -805891 78598 455884 -427506 0.97 1061285 708044 73297 -788382 66542 313506 -377880 0.84 1634396 795678 213429 -930868 65779 579791 -538952 1646297 844959 146502 3227514 44870 592051 -540033 1580343 239604 182560 -764578 53068 613756 -421879 1.04 1 0.93 lb/lb FPCM 0.66 0.54 0.72 2.1 0.65 Carbon footprint with biogenic CO2 *FPCM is fat and protein corrected milk (4.0% fat and 3.3% protein) 184 REFERENCES 185 REFERENCES Acock, B., and Trent, A. 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