EFFECT OF A BIODEGRADATION PROMOTING ADDITIVE ON POLY ETHYLENE TEREPHTHALATE IN ANAEROBIC DIGESTION B y Wataru Sato A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Packaging Master of Science 2015 ABSTRACT EFFECT OF A BIODEGRADATION PROMOTING ADDITIVE ON POLY ETHYLENE TEREPHTHALATE IN ANAEROBIC DIGESTION B y Wataru Sato Poly ethylene terephthalate sheet (PET) with a biodegradation promoting additive , provided by ENSO Plastic s , was made and evaluated in an anaerobic environment with three different inoculums: landfill leachate, wastewater treatment residue, and liquid from an anaerobic digester. As bioreactors , 125 m L glass bott les with closures were prepared, and test sample s , fresh cow manure, and inoculum s were placed into the bioreactors . The bioreactors were kept in a 35 C incubator . Gas production from the samples was measured for 90 days. Cellulose samples, pre pared as positive controls, showed higher gas production than the other samples , and its biodegradation extent reached 32.4 %, 51.6 % and 36.5 % in each inoculum , respectively. However, PET with additive samples did not show higher gas production than either blank or n eat PET in landfill leachate, wastewater treatment residue and anaerobic digester inoculums . Statistical analysis of the gas production data showed that only cellulose was significant ly different than the other samples in landfill leachate , wastewater treatment and anaerobic digester inoculums ( =0.05 ) . In conclusion , no significant difference was observed in PET with biodegradation promoting additive in this test environment. According to ENSO Plastics, the cloudiness of the PET sheets made for this experiment indicate d insufficient dispersion of the additive: t he company states that excellent dispersion is required to enhance biodegradation. iii To my family iv ACKNOWLEDGMENTS I would like to express my deep gratitude to Dr. Selke , Dr. Auras, Dr. Liu, and Aaron Walworth . My major professor , Dr. Selke , supported me during this research; discuss ing our topic, and sharing critical knowledge. Dr. Auras and Dr. Liu offered insights to run the experiment and helped me with this research. Aaron, as a lab manager, helped me to establish the experimental system in packaging lab. I also would like to thank my fellow packaging graduate stu dents especially, Tuan, Rijosh, and Edgar. They instructed me how to use instruments necessary for this research. Also, I would like to thank graduate students in College of Engineering. They helped me to obtain materials for the experiment. Lastly, I ca nnot forget to express my gratitude to Mark, Suntory, and my wife Keiko. Mark helped me to improve my English writing skill and instructed me in sophisticated expression in his writing program. My company, Suntory, gave me a chance to study packaging in MSU. Keiko has supported me, first in Japan, and throughout our life in the U.S. v TABLE OF CONTENTS LIST OF TABLES ................................ ................................ ................................ ......................... v ii LIST OF FIGURES ................................ ................................ ................................ ...................... i x KEY TO ABBREVIATIONS ................................ ................................ ................................ ........... x CHAPTER 1 ................................ ................................ ................................ ................................ .. 1 INTRODUCTION ................................ ................................ ................................ .......................... 1 1.1 Background ................................ ................................ ................................ ................. 1 1.2 Motivation ................................ ................................ ................................ .................... 3 1.3 Goal and objectives ................................ ................................ ................................ ..... 4 CHAPTER 2 ................................ ................................ ................................ ................................ .. 5 LITERATURE REVIEW ................................ ................................ ................................ ................ 5 2.1 PET ................................ ................................ ................................ ............................. 5 2.2 Biodegradation ................................ ................................ ................................ ............ 7 2.3 Anaerobic digestion ................................ ................................ ................................ ..... 8 2.4 Landfill ................................ ................................ ................................ ....................... 10 2.5 Biodegradable plastics ................................ ................................ .............................. 12 2. 6 Pro d egradant additives for biodegradation ................................ ............................... 14 2.7 Test st andards for anaerobic digestion ................................ ................................ ..... 17 CHAPTER 3 ................................ ................................ ................................ ................................ 20 MATERIALS AND METHOD S ................................ ................................ ................................ .... 20 3.1 PET production process ................................ ................................ ............................ 20 3.2 Anaerobic digestion system ................................ ................................ ...................... 22 3.3 Sample preparation ................................ ................................ ................................ ... 23 3.4 Gas measurement ................................ ................................ ................................ ..... 25 3.5 pH adjustment ................................ ................................ ................................ ........... 27 3.6 Estimated gas production ................................ ................................ .......................... 28 CHAPTER 4 ................................ ................................ ................................ ................................ 30 RESULTS AND DISCUSSION ................................ ................................ ................................ ... 30 4 .1 Cumulative gas volume ................................ ................................ ............................. 30 4.2 Bio d egradation extent ................................ ................................ ............................... 34 4 .3 Statistical analysis ................................ ................................ ................................ ..... 36 CHAPTER 5 ................................ ................................ ................................ ................................ 38 CONCLUSION S AND FUTURE WORK ................................ ................................ ..................... 38 5.1 Conclusion s ................................ ................................ ................................ ............... 38 5 .2 Recommendations ................................ ................................ ................................ .... 39 APPENDICES ................................ ................................ ................................ ............................. 41 APPENDIX A: CHN composition of samples ................................ ................................ .. 42 APPENDIX B : Solid content and organic content of manure and inoculums .................. 43 APPENDIX C : Temperature control capability of the oven ................................ ............. 45 APPENDIX D : p H adjustment of the bioreactors ................................ ............................. 4 6 vi APPENDIX E : Original gas evolution data of each bioreactor ................................ ........ 47 APPENDIX F : Original biodegradation extent data of each bioreactor ........................... 62 BIBLIO GRAPHY ................................ ................................ ................................ ......................... 74 vii LIST OF TABLES Table 2 - 1 Major properties of PET, adapted from [ 8 ] ................................ ................................ .... 6 Table 2 - 2 Fa ctors affecting Biodegradation, adapted from [ 14 ] ................................ .................... 8 Table 2 - 3 Summary of the AST M standards for anaerobic tests ................................ ................ 19 Table 3 - 1 Thickness of test sheets ................................ ................................ ............................. 21 Table 3 - 2 COD values ................................ ................................ ................................ ................ 23 Table 3 - 3 Amou nt s of materials in a bioreactor ................................ ................................ .......... 24 Table 3 - 4 Number of samples ................................ ................................ ................................ ..... 25 Table 3 - 5 Initial pH of samples ................................ ................................ ................................ ... 27 Table 3 - 6 Estimated gas production ................................ ................................ ........................... 29 Table 4 - 1 Average c umulative gas volume at 90 days ................................ ............................... 31 Table 4 - 2 B iodegradation extent at 90 days ................................ ................................ ............... 36 Table 4 - 3 T - test results of cumulative gas volume wi th landfill leachate at 90 days ................... 37 Table 4 - 4 T - test results of cumulative gas volume with wastewat er treatment residue at 90 days ................................ ................................ ................................ ................................ .................... 37 Table 4 - 5: T - test results of cumulative gas volume with anaerobic digester at 90 days ............. 37 Table A - 1 CHN data of samples ................................ ................................ ................................ . 42 Table B - 1 Solid content and organic content of manure ................................ ............................. 4 3 Table B - 2 Solid contents of inoculums ................................ ................................ ........................ 44 Table D - 1 Amount of added NaOH (10 wt %) ................................ ................................ ............. 46 Table E - 1 Blank (only manure) with landfill leachate ................................ ................................ .. 47 Table E - 2 Cellulose (0.55 g) with landfill leachate ................................ ................................ ...... 48 Table E - 3 Neat PET (3.00 g) with landfill leachate ................................ ................................ ..... 49 Table E - 4 PET with 1 % additive (3.00 g) with landfill leachate ................................ .................. 50 Table E - 5 PET with 5 % additive (3.00 g) with landfill leachate ................................ .................. 51 viii Table E - 6 Blank (only manure) wi th wastewater treatment residue ................................ ............ 52 Table E - 7 Cellulose (0.55 g) wi th wastewater treatment residue ................................ ................ 53 Table E - 8 Neat PET (3.00 g) wi th wastewater treatment residue ................................ ............... 54 Table E - 9 PET with 1 % additive (3.00 g) wi th wastewater treatment residue ........................... 55 Table E - 10 PET with 5 % additive (3.00 g) wi th wastewater treatment residue .......................... 56 Table E - 11 Blank (only manure) with anae robic digester ................................ ........................... 57 Table E - 12 Cellulose (0.55 g) with anaerobic dig ester ................................ ............................... 58 Table E - 13 Neat PET ( 3.00 g) with anaerobic digester ................................ .............................. 59 Table E - 14 PET with 1 % additive ( 3.00 g) with anaerobic digester ................................ ........... 60 Table E - 15 PET with 5 % additive ( 3.00 g) with anaer obic digester ................................ ........... 61 Table F - 1 Cellulose (0.55 g) with landfill leachate ................................ ................................ ...... 62 Table F - 2 Neat PET (3.00 g) with landfill leachate ................................ ................................ ..... 63 Table F - 3 PET with 1 % additive (3.00 g) with landfill leachate ................................ .................. 64 Table F - 4 PET with 5 % additive (3.00 g) with landfill leachate ................................ .................. 65 Table F - 5 Cellulose (0.55 g) wi th wastewater treatment residue ................................ ................ 66 Table F - 6 Neat PET (3.00 g) wi th wastewater treatment residue ................................ ............... 67 Table F - 7 PET with 1 % additive (3.00 g) wi th wastewater treatment residue ............................ 68 Table F - 8 PET with 5 % additive (3.00 g) wi th wastewater treatment residue ............................ 69 Table F - 9 Cellulose (0.55 g) with anaerobic dig ester ................................ ................................ . 70 Table F - 10 Neat PET ( 3.00 g) with anaerobic digester ................................ ............................... 71 Table F - 11 PET with 1 % additive ( 3.00 g) with anaerobic digester ................................ ........... 72 Tab le F - 12 PET with 5 % additive ( 3.00 g) with anaerobic digester ................................ ........... 73 ix LIST OF FIGURES Figure 1 - 1 Waste manageme nt in the world, adapted from [ 2] ................................ ..................... 2 Figure 1 - 2 Plastic productio n in the world, adapted from [ 4] ................................ ......................... 3 Figure 2 - 1 PET structure ................................ ................................ ................................ ............... 6 Figure 2 - 2 The components of MSW after recycling and composting in 2012 in the U.S., adapted from [ 1 ] ................................ ................................ ................................ .......................... 12 Figure 2 - 3 Chemical structure of furanone compounds, 3,5 - dimethyl - pentenyl - dihydro - 2(3H) - furanone (left) and N - acrylhomoserine lactone (right) ................................ ................................ 17 Figure 3 - 1 C ast film extr uder in the School of Packaging lab ................................ ..................... 21 Figure 3 - 2 Gas measurement system ................................ ................................ ......................... 26 Figure 4 - 1 Cumulative gas of test samples with landfill leachate ................................ ............... 3 2 Figure 4 - 2 Cumulative gas of test samples wi th wastewater treatment residue ......................... 33 Figure 4 - 3 Cumulative gas of test samples with anaerobic digester ................................ ........... 34 Figure C - 1 Temperature record in oven ................................ ................................ ...................... 45 x KEY TO ABBREVIATIONS ABS A crylonitrile butadiene styrene ASTM American Society for Testing and Materials CaCO 3 C alcium carbonate Ce C erium Co C obalt Cu Copper CH 4 Methane CHN Carbon, hydrogen and nytrogen CO 2 Carbon dioxide COD C hemical oxygen demand DSC D ifferential scanning calorimetry EVA E thylene vinyl acetate EVOH Ethylene vinyl alcohol Fe Iron FTIR Fourier transform infrared spectroscopy IPCC Intergovernmental Panel on Climate Change ISO International Organization for Standardization LDPE Low density polyethylene Mn M anganese MSW Municipal solid waste NaOH S odium hydrate Ni Nickel OECD Organization for Economic Cooperation and Development PBAT P olybutylene adipate - co - terephthalate xi PBS P oly butylenesuccinate PBSA P olybutylene succina te - co - adipate PCL P olycaprolactone PE Polyethylene PET Polyethylene terephthalate PHAs Polyhydroxyalkanoates PHB P olyhydroxybutyrate PLA Polylactic acid PP P olypropylene PS P olystyrene PU Poly urethane PVC P olyvinyl chloride RH Relative humidity SEM S canning electron microscope STP S tandard temperature and pressure T g G lass transition temperature TGA T hermal gravimetric analysis T m Melting temperature UV Ultraviolet WTE Waste to energy WVTR Water vapor transmission rate 1 CHAPTER 1 INTRODUCTION 1.1 Background As societies become more advanced, consumption is promoted, and municipal solid waste (MSW) is becoming a serious concern all over the world. Higher income countries are suffering from large amounts of wastes, and lower income countries are suffering from inappropriately treated wastes. According to the MSW fact sheet in U.S., MSW generated was 88.1 million tons in 1960, but this increased to 250.9 million tons in 2012 [1]. Based on the available data in 2012, 20 countries in the Organization for Economic Co - operation and Development (OECD), which are mostly developed countries, generated 572 million ton s o f solid w aste per year , and this was 44 % of the waste in the world. Based on the same data, 1,289 million ton s of solid w aste per year is produced currently in the world, and it is estimated to almost double, to 2,215 million ton s of solid w aste per year , by 2025 [2]. Not only is the amount of waste, but also waste management a serious problem. Landfill is the most common method; it was 44 % of all waste disposal in the world. The most desired method, recycling , was relatively low; 17 % in the world (Figu re 1 - 1). In the U.S., landfill was 53.8 % followed by 34.5 % recovery and 11.7 % energy recovery in 2012 [2]. In Europe , landfill was approximately 45 % followed by 35 % recycling and 20 % incineration in 2011 [3]. In developing countries, landfill is oper ated poorly, and it is appropriate to call it controlled dumping. In undeveloped countries, open dumping and open burning are the dominant methods. Looking at the composition of the waste, plastic has been significantly increasing since it s innovation. F igure 1 - 2 shows the increase of plastic production in the world. In the U.S., plastic constitute d 12.7 % of MSW generation in 2012, and in the world, it constitute d 10 % of MSW generation [1] [2]. Investigating further, packages generate a large percentage of plastic 2 waste. In Europe, packaging constituted 39.4 % of total plastic demand in 2011 [4], and in the U.S., plastic waste of containers and packages was 13.78 million tons and constituted 43.4 % of to tal plastic waste g eneration (31.75 million tons) i n 2012 [1]. To achieve a sustainable system, plastic recycling is important. For the package industries, the recycling rate of polyethylene terephthalate (PET) bottles is valuable since PET is one of the most widely used materials for packages. In the U.S ., the recycling rate of PET bottles was 31.2 % in 2012, an increase from 19.6 % in 2003 [5]. In Europe, the recycling rate of PET bottles was 52.3 % in 2012 [6]. Some countries have achieved relatively high recycling rate. For example, in Japan, the recycling rate of PET bottles was 85.8 % in 2013 [7]. Figure 1 - 1 Waste management in the world, adapted from [2]. Note: unit is million tons. Landfill, 335, 44% Recycled, 130, 17% WTE, 120, 16% Dump, 70, 9% Compost, 65, 8% Other, 45, 6% 3 Figure 1 - 2 Plastic production in the world, adapted from [4]. 1.2 Motivation To reduce environmental impact and maintain sustainability , recycling should be the highest priority. However, the recycling rate is relatively low all over the world, as the data indicated in chapter 1 - 1. Unfortunately, the most common disposal method cur rently is landfill. Therefore, another way to reduce environmental impact of disposal is required. One answer is expanding the biodegradable plastic applications. There are two approaches to try to make biodegradable plastic; one is to use originally biode gradable plastic, such as polylactic acid (PLA) and p olycaprolactone (PCL), and another way is to make conventional plastic biodegradable with prodegradant additive s. Both ways have advantages and disadvantages. An 0 50 100 150 200 250 300 1950 1976 1989 2002 2009 2010 2011 Plastic production (million tons) year 4 advantage of originally biodegradable pla stics is their relatively high biodegradability. However, typically they are inferior to conventional plastics in properties, applications , or costs. Conversely , although conventional plastics with prodegradant tend to have relatively low biodegradability , they have large potential applications once sufficient biodegradability is achieved . 1.3 Goal and objectives In this study, to overcome the environmental problem of plastic package disposal, especially targeting PET packages disposed in a landfill environm ent, the effect of a biodegradation additive for P ET was investigated in anaerobic condition s . PET was selected as the test object because it is one of the most widely used materials in packaging, and anaerobic was selected as a test condition because it simulates a landfill environment , which is the most common disposal method. 5 CHAPTER 2 LITERATURE REVIEW 2.1 PET PET is one of the most widely used plastics for packages, especially i n the beverage indust ry as soft drink bottles. The structure of PET is shown in Figure 2 - 1. PET is produced by a condensation reaction between dimethyl terephthalate or terephthalic acid and ethylene glycol. The dimethyl terephthalate and terephthalic acid are converted from para - xylene. The ethylene glycol is converted from ethylene . PET is mainly processed by injection blow molding or injection stretch blow molding. Injection blow molding is used for production of small bottles such as pharmaceutical bott les. Injection stretch blow molding is used for the majority of PET bottles because the biaxial orientation improves mechanical properties. Extrusion blow molding is not suitable for PET due to its low melt strength. PET has acceptable barrier properties f or oxygen and carbon dioxide [8]. Due to the light weight trend in many industries, the barrier properties of PET containers are being reduced, so barrier technologies such as coating s are being developed. Table 2 - 1 shows the major properties of PET. To reduce the environmental impact of PET production, bio - based PET is being developed. The development of bio - based ethylene glycol has succeeded and is now used commercially for several products, for instance, Dasani water bottles, produced b y Coca - Cola Co [9]. PET consists of 30% ethylene glycol, and the remaining 70% is terephthalic acid . Commercialization of bio - based terephthalic acid has not yet succeeded, and is still in the pilot production level [10]. In 2012 in the U.S., 2,790 thousa nd tons of P ET bottles and jars were produced, 860 thousand tons (30.8 %) were recycled , and 1,930 thousand tons were discarded [1]. In 2013, 6 1.1 trillion units of beverage packages were produced worldwide ; 404.9 billion units were rigid plastics, and 93 % of the rigid plastics were PET bottles [11]. Figure 2 - 1 PET structure. Table 2 - 1 Major properties of PET, adapted from [8]. T g 73 - 80 C (163 - 176 F) T m 245 - 265 C (473 - 509 F) Density 1.29 - 1.40 g/cm 3 Typical yield, 25 m (1 mil) film 30 m 2 /kg (21,100 in 2 /lb) Tensile strength 48.2 - 72.3 mPa (7.0 - 10.5 x 10 3 psi) Tensile modulus 2,756 - 4,135 mPa (4 - 6 x 10 5 psi) Elongation at break 30 - 3,000 % Tear strength, film 30 g/25 m (0.066 lb/mil) WVTR 390 - 510 g m/m 2 day at 37.8 C, 90 % RH (1.0 - 1.3 g mil/100 in 2 24 h at 100 F, 90% RH) O 2 permeability, 25 C 1.2 - 2.4 x 10 3 cm 3 m/m 2 d atm (3.0 - 6.1 cm 3 mil/100 in 2 24h atm) CO 2 permeability, 25 C 5.9 - 9.8 x 10 3 cm 3 m/m 2 d atm (15 - 25 cm 3 mil/100 in 2 24h atm) Water absorption, 0.32 cm thick, 24h 0.1 - 0.2 % 7 2.2 Biodegradation A biodegradable plastic can be defined as a degradable plastic in which the degradation results from the action of naturally - occurring micro - organisms suc h as bacteria, fungi, and , as stated in ASTM D883 [12]. The microorganisms degrade plastic to carbon dioxide, methane, or other small molecules. These transf ormations are caused by chemical reactions with enzymes which are produced by microorganisms. The biodegradation process can be divided into two steps, primary degradation and ultimate degradation. In the first step, primary degradation, chain scission s of the main backbone of the polymer occur and the polymer is converted into short polymer chains by hydrolysis and oxidation reactions. In the second step, ultim ate degradation, the short polymer chains are converted into carbon dioxide, biomass and water [13]. Biodegradation occurs in two situations, aerobic, the main reaction in soil and compost, and anaerobic, primarily in landfill. There are many factors whic h affect the biodegradation process. Table 2 - 2 shows a summary of the factors [14]. Increasing the temperature and moisture affects the biodegradation and hydrolysis reaction rates. However, temperature affects microorganism activity too, and if the temper ature is too high, the activity is decreased; therefore, biodegradation has an optimal temperature range. pH affects the hydrolysis reaction rate and microorganism activity too. In addition, polymer c haracteristics are important for biodegradation. For ex ample, in general, increase of molecular weight and crystal l inity decrease biodegradability. The existence of crosslinking decreases biodegradability. 8 Table 2 - 2 Factors affecting Biodegradation, adapted from [14]. Factors affecting biodegradation Exposure conditions abiotic Temperature Moisture pH UV radiation biotic Extracellular Hydrophobicity Biosurfactants Polymer Characteristics Flexibility Crystallinity Morphology Functional groups Crosslinking Molecular Weight Copolymers Blend Tacticity Additives 2.3 Anaerobic digestion Anaerobic digestion consists of three steps. In the first step , the complex organic matter is hydrolyzed into soluble molecules by fermentative bacteria. I n the second step , acid forming bacteria convert these molecules to simple organic acids, carbon dioxide and hydrogen; the principal compounds produced are acetic acid, propionic acid, butyric acid and ethanol. In the third step , methane is formed by methanogeni c bacteria, either by breaking down the acids to methane (CH 4 ) and carbon dioxide (CO 2 ) , or by bonding carbon dioxide with hydrogen to create methane and water [15] . Research on anaerobic digestion is conducted mostly in two environment s: mesophilic condit ions (approximately 35 C), which simulates a landfill environment , and thermophilic conditions (approximately 55 C), which simulates an anaerobic fermentation plant. 9 Yagi et al. conducted anaerobic digestion tests in both mesophilic and thermophilic co nditions with four bioplastic powders: PCL , PLA , polyhydroxybutyrate (PHB) and poly butylenesuccinate (PBS) . In mesophilic conditions (37 C), the biodegradation rate was in the order of PHB >> PLA > PCL. PHB biodegraded 90 % in 9 days, PLA biodegraded 29 % and 49 % in two different runs at the same conditions in 277 days, and PCL biodegraded 3 % and 22 % in two different runs at the same conditions in 277 days. PBS did not degrade [16]. In thermophil ic conditions (55 C), the biodegradation rate was in the order of PHB >> PLA > PCL. PHB biodegraded 90 % in 14 days, PLA biodegraded 80 % in 50 days, and PCL biodegraded 75 % in 75 days. PBS did not degrade [17]. Yagi et al. also investigated the effect o f sample size of PLA on biodegradation rate in thermophilic condition (55 C), and found that small pieces of PLA film (25 m) biodegraded more slowly than large pieces of PLA film, and PLA film biodegraded faster than PLA powder (125 - 250 m) [18]. The aut hors explained that small pieces floated in the sludge , and if the activity of the upper layer of the sludge was lower than the bottom, the biodegradation rate of the small pieces could be slower. Also, the total surface area of PLA film was larger than PL A powder, so the biodegradation rate of the film was higher than the powder. Hubackova et al. compared various starch types for PCL/starch blends in mesophilic conditions (35 C ), and concluded that PCL with starch plasticized with glycerol demonstrated a higher rate of biodegradation than PCL with pure starch [19]. Hermanová et al. researched poly ethylene terepht halate - co - lactate copolyesters , pr oduced from P ET waste beverage bottles and L - lactic acid , and found that the biodegradability of the samples re ached 34 - 69 % at 394 days in thermophilic conditions ( 55 C ) [20]. 10 2.4 Landfill Landfill can be said to be the bottom of the solid waste management hierarchy and the least desirable disposal method, but it is the only choice for residues from more effective ways, such as incineration . In addition, it is still the least expensive disposal method in countries which have large available area such as the U.S., and countries which do not have sophisticated disposal systems such as developing countries [21]. Landfilling has been conducted since the beginning of civilization. At first, there was no serious concern because the amount of waste was significantly less tha n in the modern era, and waste materials were organic. However, as industries expanded , the amount of waste, non - organic waste and non - biodegradable waste has increased. Pollution from landfill sites received much attention as environmental awareness grew. The lack of knowledge of treating landfill leachate allowed contamination of undergr ound water with toxic substances, such as heavy metals. Generation of methane gas is hazardous because of its risk of explosion. Methane is also known as a greenhouse gas and the Intergovernmental Panel on Climate Change (IPPC) estimates its effect is 23 times greater than that of the same volume of carbon dioxide [22]. To overcome these concerns, modern landfill technology was developed [23]. Modern landfills have three f eatures: a liner system , leachate collection system and methane collection system. First, to separate the trash and subsequent leachate from the ground water, a liner layer is made for protection on the bottom. The liner is made of clay, plastic (PE, PVC), or a combination of both. Second, to collect landfill leachate, perforated pipe is buried and the leachate is pumped up to a tank or pond. The leachate comes from the liquid content of garbage and ingress of water such as rain, and collects contaminants i ncluding hazardous substances as it percolates through the garbage. Therefore, leachate is strictly regulated by law and requires proper treatment. Typically, collected leachate is monitored to collect contaminant data and is recirculated or treated by was tewater treatment facilities. Third, 11 methane gas is generated by anaerobic bacterial activity and collected through pipes. Methane gas is used as energy for boilers and electricity generator s, or simply flared [24][25]. Figure 2 - 2 shows the components of MSW after recycling and composting in the U.S. in 2012 [1]. Biomass materials, which were paper and paper board, yard trimmings, wood, and food waste, constituted 52.8 % of the MSW. Petrochemical, which was plastics, con stitute d 17.6 %. Rubber, leather , and textiles, which constituted 11.2 %, could be either biomass material or petrochemical. The average molecular structure of organic compounds in MSW can be shown as the molecular composition of C 6 H 10 O 4 [26]. After the wa ste is landfilled, organic components start to degrade to primary CH 4 and CO 2 by anaerobic biodegradation. This process can be shown in two representative reactions [15]. Acetogenesis Methanogenesis M o re simply, the maximum amount of gas from organic compounds in anaerobic digestion can be shown in the following equation [15]. 12 Figure 2 - 2 T he components of MSW after recycling and composting in 2012 in the U.S. , adapted from [1]. 2.5 Biodegradable plastics Research on biodegradable plastics has been an active topic s ince the 1970 s, motivated by the increase of plastic waste and environmental concerns. In the early years of the research, biodegradable plastic was no t the primary goal, but disintegration of plastic was the goal to save landfill space. Copolymers of conventional polyolefin s with starch, metal oxides, or metal salts were studied, but these can only disintegrat e into small chips. As plastics became a ser ious concern, truly biodegradable plastics, such as PCL, PBS, polybutylene succinate - co - adipate (PBSA), and polybutylene adipate - co - terephthalate (PBAT) were studied. Biodegradable plastics can be categorized to three groups by their origins: n aturally occurring Foodwaste, 21.1% Plastic, 17.6% Paper & paperboard, 14.8% Rubber, leather & textiles, 11.2% Metals, 9.0% Yad trimmings, 8.7% Wood, 8.2% Glass, 5.1% Other, 4.3% 13 biodegradable polymers, biodegradable polymers derived from renewable resources , and biodegradable polymers derived from petroleum [27]. N aturally occurring biodegradable polymers have a long history. T he y have been used from ancient times as s kin of animals, plant fibers , silk, etc. At first, these polymers were not used because of high cost compared with conventional plastics. However, as the awareness of environmental pollution and depletion of fossil oil increased, the research expanded . Sta rch, cellulose, soy protein plastics, and sugar beet pulp plastics can be categorized in this group. Especially, starch - based plastic has the second largest share in the world - 41 % in 2012 - in the biodegradable plastic market, and it was the largest sha re in Europe with 62 % of the market [28]. For instance, starch - based plastic was used in plastic bags and cushion packaging. In the group of biodegradable polymers derived from renewable resources , PLA and the polyhydroxyalkanoates (PHAs) are the most im portant polymers. These polymers are not found in nature or not available in commercially beneficial form or quantity, but can be produced from naturally occurring bioresources . Especially, PLA is the most widely used and studied biodegradable polymer due to its therm al characteristics, which make it possible to use existing process equipment, and the cost is competitive when compared with petroleum - based polymers. PLA had the largest share (47%) in the biodegradable plastic market in 2012 [28]. Typically, synthetic polymers are resistant to biodegradation, though natural polymers are relatively susceptible to biodegradation . However, there are some polymers that are biodegradable and petroleum - based . Examples include PCL, PBS, and PBAT. PCL and PBS are syn thetic aliphatic polyesters, and PBAT is an aliphatic - aromatic copolymer [27]. 14 2.6 Prodegradant additives for biodegradation Since conventional plastics are usually not biodegradable, many attempts have been made to make synthetic plastic biodegradable using additives. Prodegradant technology can be categorized into three groups: transition metal salts, carbonyl containing copolymers , and chemo - taxis approaches [29]. Most prodegradant s use an oxo - biodegradation mechanism. Oxo - biodegradation is a combina tion of biodegradation and oxidation by mostly photo degradation or thermal degradation. By photo or thermal degradation, it is claimed that the molecular weight of the polymer is reduced and the polymer becomes easy to bio degrade with enzyme reactions by microorganisms. Transition metal salts are the most widely used prodegradant s for polyolefin s. Commercially available prodegradants in this group include TDPA ® [30], Reverte TM [31], AddiFlex ® [32], d 2 w [33] and P - Life [34]. TDPA ® ( EPI Environmental Produc ts Inc. , Vancouver, Canada) works by two stages of oxo - biodegradation process. According to the company s claim, i n the first stage, the long polymer molecules are reduced to shorter lengths by oxidation with heat, UV light and mechanical stress. With o xidation , the molecules become hydrophilic and small enough to be ingest ed by micro - organisms. In the second stage, biodegradation occurs by microorganism digestion. TDPA ® can be used for polyethylene (PE), polypropylene (PP) and polystyrene (PS) [30]. Act ive components of TDPA ® are metal stearates (Fe, Ce, Co) and citric acid (typically Co) [29]. Reverte TM ( Wells Plastics Ltd , UK) also works by an oxo - biodegradation process . According to the company s claim, in t he oxidation phase , polymer molecular weight is reduced and oxygen is introduced into the structure. In t he biodegrada tion phase, the lower molecular weight polymer is converted into biomass, CO 2 and H 2 O by microorganisms. Reverte TM is designed for PE, PP and PET [31]. Active components of Reverte TM are an u ndisclosed photo - inhibiting package, a metal ion prodegradant package , and biodegradation promotors (micronized cellulose) [29]. AddiFlex ® ( Add - X Biotech AB , Sweden) also works by 15 oxo - biodegradation and is used for PE according to the company s claim [32]. Active components are m etal carboxylate (Fe, Mn, Cu, Co, Ni), starch, and calcium carbonate ( CaCO 3 ). Especially, CaCO 3 plays an important role and increases UV degradation by up to 66% [29]. d 2 w ( Symphony Environmental , UK) is an o xo - biodegrada ble additive which breaks molecular chains by a process of oxidation, accelerated by light, heat and stress, according to the company s claim. Applications are PE and PP [33]. The active components are metal stearates and stabilizers (typically Mn) [29]. P - Life ( Programmable Life Inc. , U.S.) is an o xo - biodegradable additive based on a manganese salt and used for low density polyethylene (LDPE) [34]. Jakubowicz et al. used P - Life for their research on thermally oxidized LDPE in soil (23 C) and in a compost environment (58 C) , and found 91 % mineralization in soil and 43 % mineralization in a compost test after two years [35]. They explained that the reason that higher mineralization was found in the lower temperature (soil) was due to the difference of mi croorganism population between the test environments. Carbonyl containing copolymers can be divided two groups: carbon monoxide copolymers and vinyl ketone copolymers. The carbon monoxide is known as poly(ethylene - co - carbon monoxide), which is used for s ix - pack carrier rings for beverage cans and bottles. T he carbonyl group absorbs UV light and breaks polymer chains to short segments by a Norrish II reaction [29]. Vinyl ketone copolymer is commercially available as Ecolyte (Ecoplastic ltd, Ontario, Canada ) [36]. Just like carbon monoxide, the carbonyl group in ketone copolymer absorbs UV light and induces photodegradation. However, these are not claimed to work for biodegradation. The chemo - taxis approach uses organic additives, and it is claimed to attr act microorganisms by providing food in the additive to digest the polymer more quickly. Commercially available additives in this group are Eco - [37], EcoPure® [38], Omnidegradable TM packag ing [39], and E NSO RESTORE TM [40]. Eco - ( Ecologic LLC , WI, 16 U.S.) is a n organic additive , and according to the company s claim, the ingredients in Eco - microorganisms to form a coating (biofilm) on the surface of the plastic , and other ingredients in Eco - ructure to make room for microorganisms . The microorganisms attract additional microorganisms and break down the chemical bonds of the polymer. Eco - attracts oleophilic bacteria , which exist in landfills. Eco - One is compatible with PE , poly urethane ( PU ), PP , PET , PS , n ylon , ethylene vinyl acetate ( EVA ), a crylonitrile butadiene styrene ( ABS ), p olyvinyl chloride ( PVC ), p olycarbonate , and e thylene vinyl alcohol ( EVOH ) [37]. EcoPure® ( Bio - Tec Environmental LLC , NM, U.S.) is an organic additive , and according to the company s claim, the additive acts as a catalyst when it is exposed to enzymes , so that microorganisms will penetrate the plastic. Other ingredients expand the molecular structure, and mak e room for microorganisms, and microorganisms attra ct other microorganisms by a chemical signal , q uorum sensing . At the signal, microorganisms gather to a food source and break down chemical bonds. EcoPure® can be used for EVA, PET, PE, PP, PS, and nylon [38]. According to Anne et al. [29] and US patent 2008103232 [41], a ssignee Bio - Tec Environmental LLC , the ingredients of chemo attractants are based on furanone, and the swelling agents are natural fibers or cultured colloids. In addition , there are essential components of glutaric acid, a hexadecanoic acid compound, and polycaprolactone in a carrier resin (EVA) . F u ranone compounds are 3,5 - dimethyl - pent enyl - dihydro - 2(3H) - furanone iso mer mixtures, emoxyfurane and N - acylhomoserine lac tones (Fig 2 - 3). Furanones contain carbonyl structure s and c an act as UV absorbers. Halogenated furanones are excluded from furanone compounds because they act as quorum sensing inhibitors . Furthermore, non - is also listed as a chemo attractant . Omnidegradable TM packag ing ( TekPak Solutions,Ontario , Canada) is an organic additive , and according to the s claim, it works in landfill, soil or water. E NSO RESTORE TM ( ENSO Plastics LLC, Mesa, AZ) is an organic additive and it is claimed to induce the production of an extra - cellular enzyme from certain microorganisms. The enzyme works as the catalyst for depolymerizing the 17 plastic material , and makes polymers biodegradable. E NSO RESTORE TM is designed for PET, HDPE, LDPE, PE, PP, EVA , PS, nitrile, rubber and latex [ 40 ]. Figure 2 - 3 Chemical structure of furanone compounds, 3,5 - dimethyl - pentenyl - dihydro - 2(3H) - furanone (left) and N - acryl homoserine lactone (right). 2.7 Test stan dards for anaerobic digestion Several test standards about anaerobic digestion are defined by ASTM and ISO. The followings is a list of standards, and table 2 - 3 shows a summary of the ASTM standards. ASTM : Standard Test Method for Determining the Anaerobic Biodegradation of Plastic Materials in the Presence of Municipal Sewage Sludge [42] . ASTM D5511 12 : Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials u nder High - Solids Anaerobic - Digestion Conditions [43]. ASTM D5526 12 : Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials u nder Accelerate [44]. ASTM D7475 11 : Standard Test Method for Determining the Aerobic Degradation and Anaerobi c Biodegradation of Plastic Materials under Accelerated Conditions [45]. 18 ISO 13975:2012 : Plastics -- Determination of t he ultimate anaerobic biodegradation of plastic materials in controlled slurry digestion systems -- Method by measurement of biogas production [46]. ISO 14853:2005: Plastics -- Determination of the ultimate anaerobic biodegradation of plastic materials in an aqueous system -- Method by measurement of biogas production [47]. ISO 15985:2014: Plastics -- Determination of the ultimate anaerobic biodegradation under high - solids anaerobic - digestion conditions -- Method by analysis of released biogas [ 48 ]. 19 Tab le 2 - 3 Summary of the ASTM standards for anaerobic tests. ASTM D5210 - 92 D5511 - 12 D5526 - 12 D7475 - 11 Simulated environment Anaerobic digester municipal sewage sludge High - solids anaerobic - digestion Accelerated landfill conditions Change of environment from aerobic to anaerobic as depth of landfill increase s Temperature 37 ± 2 or pH - 7.5 - 8.5 7.5 - 8.5 7.5 - 8.5 Solid content At least 1 to 2 % Over 20% 35, 45, and 60% 35, 45, and 60% Inoculum Anaerobic - sludge digester Anaerobic digester with pretreated household waste as a sole substrate Anaerobic digester with pretreated household waste as a sole substrate Anaerobic digester with pretreated household waste as a sole substrate Other components Stock solution - Pretreated household waste Household waste and pretreated household waste Digester Serum bottle (approximately 160 m L ) Erlenmeyer flask Pressure resistant glass vessels (4L to 6L) Pressure resistant glass vessels (4L to 6L) Gas measurement method Volume Volume Pressure increase Pressure increase Incubation In the dark In the dark or diffused light In the dark In the dark Blank Inoculum medium Inoculum only Inoculum with pretreated household waste Inoculum with pretreated household waste Negative control - Polyethylene (optional) Polyethylene (optional) Polyethylene (optional) Positive control - Cellulose Cellulose Cellulose Frequency of measurements Sufficient number Five times per week At least weekly At least weekly Number of replicates Three Three Three for each solid content (9 vessels for each samples) Three for each solid content (9 vessels for each samples) 20 CHAPTER 3 MATERIALS AND METHODS 3.1 PET production process N eat PET sheet, PET sheet with 1 wt% additive , and PET sheet with 5 wt% additive were prepared for this study. PET resin , Laser+ ® W 4000 (K42A) grade , which is designed for water bottle s, was obtained from DAK Americas LLC (Chadds Ford, PA ) . The m asterbatch of the biodegradation promoting additive was obtained from ENSO Plastic s (Mesa, AZ) , and ENSO RESTORE TM PETG was used for this study. The required amount of PET resin and additive were mixed and placed into a vacuum oven. The vacuum oven was set at 120 - 30 inHg. Resins were dried for 24 hours under this condition , then cooled to room temperature and kept in vacuum condition s until they were used. PET sheet was produced using a Microtruder model RCP - 0625 extruder (Randcastle Extrusion Systems, Inc., Cedar Grove, NJ) (Figure 3 - 1) . The temperatu re profile of the extrude r was 282 - 310 - 310 - 310 - 310 ºC (540 - 590 - 590 - 590 - 590 ºF) for zone 1, zone 2, zone 3, transfer tube, and di e, respectively . The screw speed of the extruder was 500 rpm. To reduce crystal l inity of the sheets, the chill roll temperature was controlled at 21 ºC (70 ºF) and placed close to the die exit so that the sheet s were chil led rapidly. The speed of the chill roll was 20 rpm. Table 3 - 1 shows the thickness of the sheet s . The composition of the test sheets was measured by CHN analyzer ( Perkin Elmer , Waltham, Massachusetts ). The data are shown in appendix A. 21 Figure 3 - 1 Cast film extruder in the School of Packaging lab. Table 3 - 1 Thickness of test sheets. Thickness (mil) Average Minimum Maximum Neat PET 4.3 3.4 4.9 0.41 PET with 1% additive 4.4 3.5 5.5 0.62 PET with 5% additive 5.2 4.0 6.1 0.70 22 3.2 Anaerobic digestion system A simulated landfill anaerobic digestion system was established for this experiment. 125 mL glass bottles were selected as bioreactors. The caps for the bottles had c hlorobutyl rubber plugs in the center of the tops. Needles could be inserted into the bottles through the rubber plug to add or remove contents without exposing the contents to the outside air. Therefore, inside the bottle was maintained as an anaerobic environment throughout the experiment. Next, i noculum, manure and test samples were placed in the bottles. The inoculum was used as a seed source of anaerobic microorganisms. Three different inoculums, obtained from landfill leachate , wastewat er treatment residue, and an anaerobic digester, were used in this experiment to investigate how the microorganism population affected biodegradability of the test samples. The landfill leachate inoculum was obtained from a landfill site of Granger LLC (La nsing, MI). The wastewater treatment residue inoculum was obtained from Delhi Charter Township Wastewater Treatment Plant (Holt, MI). The anaerobic digester at Michigan State University provide d the anaerobic digester inoculum. Fresh cow manure was obtained from the Michigan State University dairy farm. The purpose of the manure was to provide necessary nutrition for microorganism activity. Liquid manure (5 wt % total solids content) was used for this experiment, since a lower solids content wo uld lead to higher gas generation [49]. Chemical oxygen demand (COD) of the inoculums and manure were measured by a DR 2800 Portable Spectrophotometer and Digestion Solution for COD 20 - 1500 mg/L Range ( HACH Company, Loveland, Co ). Two measurements were con ducted for each sample. Table 3 - 2 shows the COD values. After the i noculum, manure , and test samples were placed in the bottles, the air in the headspace of the bottles was replaced by nitrogen gas to make the environment anaerobic. The bioreactors were maintained at 35 ºC to simulate a ctual landfill temperature s. Throughout the 23 experiment, microorganism s degraded the manure and test samples, and produced gas which was mainly CO 2 and CH 4 . The produced gas was collected by a needle which was inserted into the bottle , so that the inside of the bottle maintained the anaerobic environment. Table 3 - 2 COD values. COD (g/L) Average COD (g/L) Manure (5 wt % solid content) 1 32.0 28.7 2 25.4 Landfill leachate 1 1.00 1.00 2 0.99 Wastewater treatment residue 1 23.2 23.0 2 22.7 Anaerobic digester 1 49.5 48.8 2 48.1 3.3 Sample preparation PET sheets were cut into 0.5 in x 0.5 in (1.27 cm x 1.27 cm) squares with a sample cutter and scissors. Five test standards , which are negative control, positive control, Neat PET, PET with 1 % additive, and PET with 5 % additive, were prepared. The negative control contained only manure and inoculum, and was used as a blank. For the positive control, cell ulo s e powder, which w as obtained from Sigma - Aldrich Co. LLC ( St. Louis, MO ), was used as a test sample. The purpose of the positive control is to confirm the biodegradation capability of the system, since cellulose is known to be a biodegradable polymer. Manure was mixed with distilled water to 5 wt % solid content and homogenized by a blender. Appendix B shows the water content and organic content of the original manure. Next, three different inoculums were placed in the bioreactors with test samples and manure. Three bioreac tors were prepared for 24 each test sample. Tables 3 - 3 and 3 - 4 show the amount of material and number of test samples . In total, 45 bioreactors, which included five test samples and three different inoculum s, were prepared. After the bioreactors were closed tightly, the air in the head space of the bioreactors was replaced with 100% nitrogen gas through two needles, which were inserted into the bottles through the caps. One needle was connected to a nitrogen cylinder and the other was for the gas to exit. Ne xt, the bioreactors were placed in the oven, which was maintained at 35 ± 2 ºC throughout the experiment. Appendix C shows the temperature control capability of the oven. After an hour, the bioreactors were removed from the oven, and the inside gas was rel eased through the needle to neutralize the initial pressure difference, which was caused by the increase of the temperature of the bioreactors from room temperature to 35 ºC . Then, the experimental measurements began. Table 3 - 3 Amounts of materials in a bioreactor. Inoculum ( mL ) Manure ( mL ) Cellulose ( g ) PET sheet ( g ) Blank (Negative control) 7.5 75 .0 Cellulose (Positive control) 7.5 75 .0 0.55 0 Neat PET 7.5 75 .0 3 .00 PET with 1 % additive 7.5 75 .0 3 .00 PET with 5 % additive 7.5 75 .0 3 .00 25 Table 3 - 4 Number of samples . Inoculum Landfill leachate Wastewater treatment residue Anaerobic digester Blank (Negative control) 3 3 3 Cellulose (Positive control) 3 3 3 Neat PET 3 3 3 PET with 1 % additive 3 3 3 PET with 5 % additive 3 3 3 3.4 Gas measurement The generated gas in the bioreactors was measured by a syphon system. Figure 3 - 2 shows the gas measurement system for the experiment. A 500 mL glass bottle was prepared and filled with water to about 80 % of maximum volume. The same cap as the bioreactor was used for the 500 mL glass bottle. Two needles were inserted into the 500 mL bottle. One was a short needle and the tip was in the head space of the bottle. The other was a long needle and the tip was on the bottom of the glass bottle. Both needles were connected to plastic tubes and the other end of the short needle tube had another needle which was inserted into the bioreactors. The other end of the long needle tube was inserted into a graduated cylinder . The internal pressure of the biorea ctor was higher than atmospheric pressure because of the generated gas, so once the needle was inserted into the bioreactor, the gas moved to the head space of the 500 mL glass bottle. The head space of the 500 mL glass bottle was pressurized by the increa se in the volume of gas, and pressurized the water in the bottle, which moved 26 through the long needle and came out into the graduated cylinder . This continued until the internal pressure of the bioreactor became equal to atmospheric pressure, and at this p oint, the volume of the generated gas was measured in the graduated cylinder as volume of the water. The measurement takes approximately three to five minutes, depending on the volume of the generated gas. The 500 mL glass bottle was refilled after the wat er volume became less than 40 % of the maximum volume. To reduce total measurement time, three sets of the same system were established and run simultaneously. Three bioreactors were removed from the oven at one time to avoid decrease in temperature. Gas leakage was checked by pouring detergent liquid on the connections such as between the rubber plug of the cap and the needles, and the needles and tubes so that if there was a leak, it was detected as bubbles. Figure 3 - 2 Gas measurement system. 27 3.5 p H adju stment The pH of the bioreactors was checked and maintained close to pH 7 throughout the experiment. The initial pH of the inoculums, manure, and bioreactors were measured using a pH meter ( PHB - 212 , OMEGA Engineering Inc. , Stamford, CT). Table 3 - 5 shows the pH data for each of these test materials. During the experiment, pH could not be measured using a pH meter because opening the cap would destroy the anaerobic environment . Therefore, pH was measured by a syringe and pH strips (Hydr ion ® pH 6.0 - 8.0, Micro Essential Laboratory Inc., Brooklyn, NY). Approximately 0.1 mL of liquid was removed from the bioreactor using a 1 mL syringe, and deposited on a pH strip. For each measurement, one of three bioreactors in each test set was selected as a representative and measured. Once the pH strip indicated the pH had fallen below 6, a 10 wt % sodium hydroxide (NaOH) solution was added to the bioreactors. According to a titration test conducted before the experiment, from pH 6 to pH 7, approximatel y 1 mL of 10 % wt NaOH solution was required for the 82.5 mL bioreactors. Appendix D shows the pH adjustment record throughout the experiment. The maximum amount of NaOH added to the sample was 2.5 ml, which equaled 3.03 g/L. This value was less than t he h alf maximal inhibitory concentration (IC 50 ) , 5.6 to 53 g/L, which reduces cumulative methane production by half [50]. Table 3 - 5 Initial pH of samples . p H Manure (5 wt % solid content) 7.79 Landfill leachate 7.21 Wastewater treatment residue 7.18 Anaerobic digester 7.25 Manure (5 wt % solid content) + landfill leachate 7.77 Manure (5 wt % solid content) + wastewater treatment residue 7.75 Manure (5 wt % solid content) + anaerobic digester 7.61 28 3.6 Estimated gas production The estimated gas production can be calculated with two methods: from COD values and CHN values. By using COD values in table 3 - 2, estimated gas production was calculated with the following equation , V gas : estimated gas production (mL) COD: COD values (g/L) COD reduction: percentage of COD reduction (%) V sample : volume of the sample (manure:75 mL, inoculum:7.5 mL) V methane /V total : the percentage of methane in total gas (%) Here, the COD reduction rate is assumed to be 30%. The volume of methane produced per 1 g COD at 35 C 1 atm, was assumed to be 0.395 L [51]. The percentage of methane in the total gas was assumed to be 60 %. Table 3 - 6 shows the estimated gas production. The estimated gas production was also calculated from CHN values in appendix A by the following equation. Here, the solid weight of 75 mL manure was 3.75 g (5 wt%), and the solid weights of the 7.5 mL inoculums were obtained from table B - 2 in appendix B. Carbon was assumed to produce either methane or carbon dioxide. The percentage of biodegradation of the manure and inoculums was assumed to be 30%. Table 3 - 6 shows the estimated gas production. 29 The differences in the estimated gas calculated from the COD values and CHN values are presumed to come from the relatively low COD values of the manure. The COD was measured with 2 ml of diluted liquid sample, for manure, it was diluted by 100 times. Therefore, lack of complete homogenization of the liquid manure may have caused the low COD value. Table 3 - 6 Estimated gas production. Estimated gas production (mL) From COD values From CHN values Manure (5 wt% solid content) 75 mL 425.1 1029.0 Landfill leachate 7.5 mL 1.5 1.8 Wastewater treatment residue 7.5 mL 34.0 24.2 Anaerobic digester 7.5 mL 72.3 53.6 Manure 75 mL + landfill leachate 7.5 mL 426.6 1030.8 Manure 75 mL + wastewater treatment residue 7.5 mL 459.1 1053.2 Manure 75 mL + anaerobic digester 7.5 mL 497.4 1082.5 30 CHAPTER 4 RESULTS AND DISCUSSION 4.1 Cumulative gas volume By following the gas measurement method in chapter 3.4, gas evolution, which produces primarily CO 2 and CH 4 , from each bioreactor , was measured and cumulative gas volume was calculated . Table 4 - 1 shows the average cumulative gas volume of three replicates o f each test sample at 90 days. Original data for each replicate are shown in appendix E. Figures 4 - 1, 4 - 2, and 4 - 3 show a comparison of the cumulative gas between test samples in different inoculums, which are landfill leachate, wastewater treatment residu e, and anaerobic digester. One of the blank samples with landfill leachate got broken accidentally after the measurement at 75 days, thus the average of two replicates was calculated for the blank of landfill leachate after 75 days. Judging from table 4 - 1 , and figures 4 - 1, 4 - 2, and 4 - 3, test samples with wastewater treatment residue and anaerobic digester show much higher gas production than landfill leachate. This is presumed due to the different microorganism activities in each inoculum . Cellulose sample s produced higher gas production than blanks in every inoculum . However, PET with additive samples did not show higher gas production than blank and n eat PET in any inoculum. Compared to the estimated gas productions in chapter 3 - 6, actual gas productions of the blank samples in every inoculums were higher. It is presumed that the COD reduction rate and percentage of biodegradation of the manure and inoculums were higher in the experiment than the 30 % assumed in the calculation. 31 Table 4 - 1 Average cumulative gas volume at 90 days. Average cumulative gas volume ( mL ) Landfill leachate Cellulose 1189.3 Neat PET 1017.0 PET with 1% additive 1025.8 PET with 5% additive 1071.2 Blank 1018.8 Wastewater treatment residue Cellulose 1448.0 Neat PET 1161.0 PET with 1% additive 1188.7 PET with 5% additive 1170.0 Blank 1176.3 Anaerobic digester Cellulose 1418.8 Neat PET 1273.2 PET with 1% additive 1251.7 PET with 5% additive 1227.2 Blank 1226.7 32 Figure 4 - 1 Cumulative gas of test samples with landfill leachate . Note: error bars show standard deviations. 33 Figure 4 - 2 Cumulative gas of test samples with wastewater treatment residue . Note: error bars show standard deviations. 34 Figure 4 - 3 Cumulative gas of test samples with anaerobic digester . Note: error bars show standard deviations. 4.2 Biodegradation extent To normalize the difference in gas evolution between the test samples and blank, the biodegradation extent was calculated with the following equation. 35 Here, C g : weight of produced gaseous carbon (g) C i : weight of carbon in test samples (g) Assuming that the produced gas contains only CO 2 and CH 4 , C g is calculated with the following equation, with correction for standard temperature and pressure (STP) by the incubator temperature (35 C) and atmospheric pressure at East Lansing (860ft, 0.96 atm). Here, C v : volume of produced gas ( mL ) From the data measured by CHN analyzer (Appendix A), C i is calculated with the following equation, For 0.55 g cellulose, C i =0.240 g, for 3.00 g neat PET, C i =1.878 g, for 3.00 g PET with 1% additive, C i =1.884 g, and for 3.00 g PET with 5% additive, C i =1.883 g, were obtained. From the above equations, the average biodegradation extent of each sample at 90 days was obtained and shown in table 4 - 2. Original biodegradation extent data are shown in appendix F. Cellulose showed a high biodegradation extent in each inoculum . However, P ET with additive did not show a high biodegradation in each inoculum . 36 Tab le 4 - 2 Biodegradation extent at 90 days. Difference to blank (mL) Biodegradation extent (%) Landfill leachate Cellulose 170.6 32.4 Neat PET - 1.7 0.0 PET with 1% additive 7.1 0.2 PET with 5% additive 52.4 1.3 Wastewater treatment residue Cellulose 271.7 51.6 Neat PET - 15.3 - 0.4 PET with 1% additive 12.3 0.3 PET with 5% additive - 6.3 - 0.2 Anaerobic digester Cellulose 192.2 36.5 Neat PET 46.5 1.1 PET with 1% additive 25.0 0.6 PET with 5% additive 0.5 0.0 4.3 Statistical analysis For the statistical analysis, t - tests ( =0.05) were conducted for the cumulative gas volume at 90 days. Tables 4 - 3, 4 - 4, and 4 - 5 show the matrix of the results of the t - test for each inoculum. Cellulose samples in every inoculum showed the t - test value less than 0.05 with other samples. In other words, the mean of cellulose samples data was significant ly different from other samples data. However, there is no value of less than 0.05 between blank, neat PET, PET with 1 % additive and PET with 5% additive in every inoculum. Therefore, there was no significant difference between these samples data. 37 Table 4 - 3 T - test results of cumulative gas volume with landfill leachate at 90 days. Neat PET PET with 1% additive PET with 5% additive Blank Cellulose 0.03 0.02 0.02 0.02 Neat PET 0.88 0.30 0.98 PET with 1% additive 0.28 0.88 PET with 5% additive 0.10 Note: T - tests values represent individual S tudent s T - test of pairs. Table 4 - 4 T - test results of cumulative gas volume with wastewater treatment residue at 90 days. Neat PET PET with 1% additive PET with 5% additive Blank Cellulose 0.00 0.00 0.00 0.00 Neat PET 0.39 0.83 0.54 PET with 1% additive 0.66 0.62 PET with 5% additive 0.87 Note: T - tests values represent individual S tudent s T - test of pairs. Table 4 - 5 T - test results of cumulative gas volume with anaerobic digester at 90 days. Neat PET PET with 1% additive PET with 5% additive Blank Cellulose 0.01 0.01 0.03 0.01 Neat PET 0.40 0.44 0.24 PET with 1% additive 0.67 0.51 PET with 5% additive 0.99 Note: T - tests values represent individual S tudent s T - test of pairs. 38 CHAPTER 5 CONCLUSIONS AND FUTURE WORK 5.1 Conclusion s In this study, the effect of a biodegradation promoting additive on PET in anaerobic digestion was investigated. The additive was kindly provided by ENSO Plastics , and three different PET sheets, which are neat PET, PET with 1 wt % additive, and 5 wt % additive, were made using the cast film extruder in the School of P ackaging lab. As the anaerobic microorganism seeds, three different inoculums were obtained from landfill leachate, wastewater treatment residue, and an anaerobic digester. A s bioreactors , 125 m L glass bottles with closures were prepared, and test samples, fresh cow manure, and inoculums were placed into the bioreactors. The bioreactors were kept in a The g as produ ced was constituted of CH 4 and CO 2 , and was measured for 90 days. Cellulose samples, prepared as positive controls, showed higher gas production than the other samples, and the cellulose biodegradation extent reached 32.4 %, 51.6 % and 36.5 % in each inoculum , respectively. PET with additive samples did not show h igher gas production than either blank or neat PET in landfill leachate, wastewater treatment residue and anaerobic digester inoculums. Statistical analysis of the gas production data showed that only cellulose was significant ly different than the other sa mples in landfill leachate, wastewater treatment and anaerobic digester inoculums ( =0.05). In conclusion, no significant difference was observed in PET with biodegradation promoting additive in this test environment. According to ENSO Plastics, the cloudi ness of the PET sheets made for this experiment indicate d insufficient dispersion of the additive: the company states that excellent dispersion is required to enhance biodegradation. 39 After the measurement at 90 days, the bioreactors were opened and test PET samples were collected and visually inspected with eyes and a microscope. Compared to the original samples, test PET samples still kept original shapes and no visual differences were observed. Due to the short experimental period, each bioreactor was still producing gas at 90 days, although the gas evolution rates were much smaller than at the peak time. Therefore, there is a possibility that the result would change in an experiment with longer time. The gas production of the cellulose samples was not steady compared to the blank samples, and was less than the blank at some points. The reason may be because the initial pH drop of the cellulose samples was much higher than for the blank samples, and low pH could inhibit the microorganism growth, or even reduce the microorganism population. Thus, lower microorganism activity resulted in lower gas production. One of the objectives of this research was to investigate the effect of different microorganism populations on biodegradation . Although gas product ion in the wastewater treatment residue and anaerobic digester inoculums was generally higher than in the landfill leachate inoculum, the differences for the PET samples were not statistically significant as for these samples the differences were relativel y small. 5.2 Recommendations This study, because of its limited nature, can provide only preliminary results and suggestion s for additional research. First, this study was conducted in one condition, which was mesophilic temperature (35 C) and relatively low solid content (5 wt % manure). Investigating different conditions, for instance thermophilic conditions (55 C) or high solid content (over 30 %) may have different results. Second, in this study, the effect of biodegradation was judg ed by only gas production, but further analytical approaches, for instance, differential scanning 40 calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) , and scanning electron microscop y (SEM) , may provide oth er insights to this study. Third, since low dispersion of the additive in the PET sheet may reduce the effect of the additive, running another experiment with PET sheets produced using a different type of extruder, which can disperse the additive more eff iciently , for instance, a twin screw extruder, or using a commercial size extruder, may produce different results. 41 APPENDICES 42 APPENDIX A: CHN composition of samples Table A - 1 CHN data of samples . Wt% C H N Cellulose 43.68 6.42 0.04 Neat PET 62.59 4.23 0.01 PET with 1% additive 62.80 4.24 0.02 PET with 5% additive 62.78 4.29 0.01 Manure 43.43 5.74 2.36 Landfill leach ate 8.27 0.69 0.28 Wastewater treatment residue 36.49 5.33 5.18 Anaerobic digester 41.87 5.45 3.64 Note: Data shows the average of three measurements. All samples were dried by oven before measurements to prevent error caused by moisture. 43 APPENDIX B: Solid content and organic content of manure and inoculums Table B - 1 Solid content and organic content of manure . Sample 1 2 3 Average Cup (g) 12.3427 12.9071 12.9694 Cup + wet manure (g) 21.0598 22.1419 20.3208 Wet manure (g) 8.7171 9.2348 7.3514 Cup + dried manure (g) 13.8810 14.4653 14.2466 Dried manure (g) 1.5383 1.5582 1.2772 Total solid content (%) 17.6 16.9 17.4 17.3 Cup + ash (g) 12.5397 13.1136 13.1375 Ash (g) 0.1970 0.2065 0.1681 Volatile solid content (%) 87.2 86.7 86.8 86.9 Note: To make 1L of 5 wt % solid manure, 289.3 g of manure and 710.7 g of water was mixed. In total, 4L of manure was made for the experiment. 44 Table B - 2 Solid contents of inoculums . Solid content Landfill leachate 0.47% Wastewater treatment residue 1.40% Anaerobic digester 2.70% Note: Data was measured by moisture analyzer ( AnD MX - 50 , A&D company ltd, Japan). 45 APPENDIX C: Temperature control capability of the oven Figure C - 1 Temperature record in oven. Note: Sampling time of a temperature recorder was set up at every 5 minutes . 33 34 35 36 37 0 4 8 12 16 20 24 Temperature in oven (ºC) Hours 46 APPENDIX D: pH adjustment of the bioreactors Table D - 1 Amount of added NaOH (10 wt %). Amount of added NaOH ( mL ) Day s Test samples Inoculum 8 10 20 Blank Landfill leachate 1.0 0.5 Wastewater treatment residue 1.0 Anaerobic digester 1.0 0.5 Cellulose Landfill leachate 1.0 1.0 0.5 Wastewater treatment residue 1.0 1.0 Anaerobic digester 1.0 1.0 0.5 Neat PET Landfill leachate 1.0 0.5 Wastewater treatment residue 1.0 Anaerobic digester 1.0 0.5 PET with 1 % additive Landfill leachate 1.0 0.5 Wastewater treatment residue 1.0 Anaerobic digester 1.0 0.5 PET with 5 % additive Landfill leachate 1.0 0.5 Wastewater treatment residue 1.0 Anaerobic digester 1.0 0.5 47 APPENDIX E: Original gas evolution data of each bioreactor Table E - 1 Blank (only manure) with landfill leachate . Note: Sample No.2 was accidentally broken after 75 days measurement. Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 24.0 24.5 25.0 24.0 24.5 25.0 24.5 25.0 24.0 0.4 5 18.5 23.5 17.5 42.5 48.0 42.5 44.3 48.0 42.5 2.6 8 15.5 21.0 21.0 58.0 69.0 63.5 63.5 69.0 58.0 4.5 10 9.0 8.5 17.0 67.0 77.5 80.5 75.0 80.5 67.0 5.8 12 11.0 9.0 15.0 78.0 86.5 95.5 86.7 95.5 78.0 7.1 15 17.0 14.5 15.0 95.0 101.0 110.5 102.2 110.5 95.0 6.4 20 40.0 99.0 30.0 135.0 200.0 140.5 158.5 200.0 135.0 29.4 29 168.5 150.0 212.0 303.5 350.0 352.5 335.3 352.5 303.5 22.5 33 72.0 67.5 82.0 375.5 417.5 434.5 409.2 434.5 375.5 24.8 36 78.0 29.5 48.5 453.5 447.0 483.0 461.2 483.0 447.0 15.7 39 80.5 19.0 32.5 534.0 466.0 515.5 505.2 534.0 466.0 28.7 43 100.5 42.0 28.0 634.5 508.0 543.5 562.0 634.5 508.0 53.3 47 88.5 113.5 20.5 723.0 621.5 564.0 636.2 723.0 564.0 65.7 50 47.5 74.0 10.0 770.5 695.5 574.0 680.0 770.5 574.0 81.0 55 60.5 97.0 15.5 831.0 792.5 589.5 737.7 831.0 589.5 105.9 59 55.5 68.5 28.0 886.5 861.0 617.5 788.3 886.5 617.5 121.2 64 32.0 32.0 64.0 918.5 893.0 681.5 831.0 918.5 681.5 106.2 68 22.0 28.5 86.0 940.5 921.5 767.5 876.5 940.5 767.5 77.5 75 36.0 59.0 138.5 976.5 980.5 906.0 954.3 980.5 906.0 34.2 84 26.0 - 65.0 1002.5 - 971.0 986.8 1002.5 971.0 15.8 90 21.0 - 43.0 1023.5 - 1014.0 1018.8 1023.5 1014.0 4.8 48 Table E - 2 Cellulose (0.55 g) with landfill leachate . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 24.0 23.5 25.5 24.0 23.5 25.5 24.3 25.5 23.5 0.8 5 31.0 30.5 29.5 55.0 54.0 55.0 54.7 55.0 54.0 0.5 8 23.5 24.5 22.0 78.5 78.5 77.0 78.0 78.5 77.0 0.7 10 20.0 28.0 21.0 98.5 106.5 98.0 101.0 106.5 98.0 3.9 12 64.0 0.0 47.5 162.5 106.5 145.5 138.2 162.5 106.5 23.4 15 31.0 53.0 26.0 193.5 159.5 171.5 174.8 193.5 159.5 14.1 20 24.0 50.0 30.5 217.5 209.5 202.0 209.7 217.5 202.0 6.3 29 218.0 220.0 198.0 435.5 429.5 400.0 421.7 435.5 400.0 15.5 33 127.0 65.0 113.0 562.5 494.5 513.0 523.3 562.5 494.5 28.7 36 87.5 25.0 100.0 650.0 519.5 613.0 594.2 650.0 519.5 54.9 39 98.5 22.5 78.5 748.5 542.0 691.5 660.7 748.5 542.0 87.1 43 66.5 31.0 46.5 815.0 573.0 738.0 708.7 815.0 573.0 100.9 47 53.5 46.0 31.5 868.5 619.0 769.5 752.3 868.5 619.0 102.6 50 42.0 64.5 13.5 910.5 683.5 783.0 792.3 910.5 683.5 92.9 55 39.0 129.0 26.0 949.5 812.5 809.0 857.0 949.5 809.0 65.4 59 32.0 57.0 48.5 981.5 869.5 857.5 902.8 981.5 857.5 55.8 64 12.0 28.5 16.0 993.5 898.0 873.5 921.7 993.5 873.5 51.8 68 9.5 33.5 9.0 1003.0 931.5 882.5 939.0 1003.0 882.5 49.5 75 28.5 153.0 76.0 1031.5 1084.5 958.5 1024.8 1084.5 958.5 51.7 84 42.0 73.0 205.0 1073.5 1157.5 1163.5 1131.5 1163.5 1073.5 41.1 90 62.5 46.0 65.0 1136.0 1203.5 1228.5 1189.3 1228.5 1136.0 39.1 49 Table E - 3 Neat PET (3.00 g) with landfill leachate . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 25.0 26.5 29.0 25.0 26.5 29.0 26.8 29.0 25.0 1.6 5 18.0 17.0 19.0 43.0 43.5 48.0 44.8 48.0 43.0 2.2 8 15.0 15.5 14.0 58.0 59.0 62.0 59.7 62.0 58.0 1.7 10 8.0 10.0 7.0 66.0 69.0 69.0 68.0 69.0 66.0 1.4 12 7.5 9.0 12.5 73.5 78.0 81.5 77.7 81.5 73.5 3.3 15 17.0 13.0 21.0 90.5 91.0 102.5 94.7 102.5 90.5 5.5 20 49.0 44.0 141.5 139.5 135.0 244.0 172.8 244.0 135.0 50.4 29 189.5 201.0 145.0 329.0 336.0 389.0 351.3 389.0 329.0 26.8 33 75.0 89.5 82.0 404.0 425.5 471.0 433.5 471.0 404.0 27.9 36 67.0 71.0 33.5 471.0 496.5 504.5 490.7 504.5 471.0 14.3 39 38.0 42.5 30.5 509.0 539.0 535.0 527.7 539.0 509.0 13.3 43 53.5 47.5 33.0 562.5 586.5 568.0 572.3 586.5 562.5 10.3 47 40.0 33.0 31.5 602.5 619.5 599.5 607.2 619.5 599.5 8.8 50 37.0 26.5 26.5 639.5 646.0 626.0 637.2 646.0 626.0 8.3 55 106.0 115.0 35.0 745.5 761.0 661.0 722.5 761.0 661.0 43.9 59 96.0 85.0 33.0 841.5 846.0 694.0 793.8 846.0 694.0 70.6 64 62.5 25.0 10.5 904.0 871.0 704.5 826.5 904.0 704.5 87.3 68 40.5 14.0 9.5 944.5 885.0 714.0 847.8 944.5 714.0 97.7 75 50.5 34.5 45.0 995.0 919.5 759.0 891.2 995.0 759.0 98.4 84 37.0 77.0 51.5 1032.0 996.5 810.5 946.3 1032.0 810.5 97.1 90 26.5 62.5 123.0 1058.5 1059.0 933.5 1017.0 1059.0 933.5 59.0 50 Table E - 4 PET with 1 % additive (3.00 g) with landfill leachate . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 27.0 28.0 28.5 27.0 28.0 28.5 27.8 28.5 27.0 0.6 5 19.0 18.0 20.0 46.0 46.0 48.5 46.8 48.5 46.0 1.2 8 15.0 14.5 21.0 61.0 60.5 69.5 63.7 69.5 60.5 4.1 10 11.0 7.0 12.0 72.0 67.5 81.5 73.7 81.5 67.5 5.8 12 10.0 8.5 10.0 82.0 76.0 91.5 83.2 91.5 76.0 6.4 15 14.0 14.0 10.5 96.0 90.0 102.0 96.0 102.0 90.0 4.9 20 46.0 54.5 38.5 142.0 144.5 140.5 142.3 144.5 140.5 1.6 29 179.5 186.0 202.0 321.5 330.5 342.5 331.5 342.5 321.5 8.6 33 112.0 115.0 77.0 433.5 445.5 419.5 432.8 445.5 419.5 10.6 36 103.0 127.5 76.5 536.5 573.0 496.0 535.2 573.0 496.0 31.4 39 45.5 99.0 48.0 582.0 672.0 544.0 599.3 672.0 544.0 53.7 43 36.0 100.5 80.0 618.0 772.5 624.0 671.5 772.5 618.0 71.5 47 23.0 78.0 102.0 641.0 850.5 726.0 739.2 850.5 641.0 86.0 50 13.5 43.0 61.5 654.5 893.5 787.5 778.5 893.5 654.5 97.8 55 14.0 44.5 70.0 668.5 938.0 857.5 821.3 938.0 668.5 113.0 59 29.5 42.0 55.0 698.0 980.0 912.5 863.5 980.0 698.0 120.2 64 45.5 22.5 24.0 743.5 1002.5 936.5 894.2 1002.5 743.5 109.9 68 54.0 15.0 12.0 797.5 1017.5 948.5 921.2 1017.5 797.5 91.9 75 98.0 34.0 23.0 895.5 1051.5 971.5 972.8 1051.5 895.5 63.7 84 55.0 22.0 17.0 950.5 1073.5 988.5 1004.2 1073.5 950.5 51.4 90 34.0 16.0 15.0 984.5 1089.5 1003.5 1025.8 1089.5 984.5 45.7 5 1 Table E - 5 PET with 5 % additive (3.00 g) with landfill leachate . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 28.5 30.0 28.5 28.5 30.0 28.5 29.0 30.0 28.5 0.7 5 17.0 20.0 18.0 45.5 50.0 46.5 47.3 50.0 45.5 1.9 8 17.5 16.5 15.0 63.0 66.5 61.5 63.7 66.5 61.5 2.1 10 8.5 9.0 12.0 71.5 75.5 73.5 73.5 75.5 71.5 1.6 12 8.0 7.0 11.5 79.5 82.5 85.0 82.3 85.0 79.5 2.2 15 16.0 16.0 15.0 95.5 98.5 100.0 98.0 100.0 95.5 1.9 20 50.0 54.0 47.0 145.5 152.5 147.0 148.3 152.5 145.5 3.0 29 186.0 179.0 210.0 331.5 331.5 357.0 340.0 357.0 331.5 12.0 33 122.0 111.5 91.5 453.5 443.0 448.5 448.3 453.5 443.0 4.3 36 119.0 77.5 43.0 572.5 520.5 491.5 528.2 572.5 491.5 33.5 39 93.0 83.0 32.5 665.5 603.5 524.0 597.7 665.5 524.0 57.9 43 87.5 100.0 96.5 753.0 703.5 620.5 692.3 753.0 620.5 54.7 47 66.0 81.0 119.5 819.0 784.5 740.0 781.2 819.0 740.0 32.3 50 43.5 52.5 78.0 862.5 837.0 818.0 839.2 862.5 818.0 18.2 55 48.0 52.5 71.0 910.5 889.5 889.0 896.3 910.5 889.0 10.0 59 51.0 51.5 50.0 961.5 941.0 939.0 947.2 961.5 939.0 10.2 64 27.5 27.0 21.0 989.0 968.0 960.0 972.3 989.0 960.0 12.2 68 18.0 18.0 12.0 1007.0 986.0 972.0 988.3 1007.0 972.0 14.4 75 35.0 35.0 21.0 1042.0 1021.0 993.0 1018.7 1042.0 993.0 20.1 84 39.0 25.5 31.0 1081.0 1046.5 1024.0 1050.5 1081.0 1024.0 23.4 90 23.0 16.0 23.0 1104.0 1062.5 1047.0 1071.2 1104.0 1047.0 24.1 52 Table E - 6 Blank (only manure) with wastewater treatment residue . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 33.5 36.5 30.5 33.5 36.5 30.5 33.5 36.5 30.5 2.4 5 39.0 34.0 39.5 72.5 70.5 70.0 71.0 72.5 70.0 1.1 8 48.0 45.0 47.0 120.5 115.5 117.0 117.7 120.5 115.5 2.1 10 41.5 37.0 33.0 162.0 152.5 150.0 154.8 162.0 150.0 5.2 12 59.5 57.5 41.0 221.5 210.0 191.0 207.5 221.5 191.0 12.6 15 79.0 70.0 80.0 300.5 280.0 271.0 283.8 300.5 271.0 12.3 20 114.5 129.0 118.5 415.0 409.0 389.5 404.5 415.0 389.5 10.9 29 209.0 250.0 253.0 624.0 659.0 642.5 641.8 659.0 624.0 14.3 33 95.0 111.5 122.5 719.0 770.5 765.0 751.5 770.5 719.0 23.1 36 59.0 60.5 66.5 778.0 831.0 831.5 813.5 831.5 778.0 25.1 39 58.0 58.5 62.5 836.0 889.5 894.0 873.2 894.0 836.0 26.3 43 58.0 62.0 62.5 894.0 951.5 956.5 934.0 956.5 894.0 28.4 47 51.5 45.5 47.5 945.5 997.0 1004.0 982.2 1004.0 945.5 26.1 50 29.5 28.0 27.0 975.0 1025.0 1031.0 1010.3 1031.0 975.0 25.1 55 34.0 30.5 22.0 1009.0 1055.5 1053.0 1039.2 1055.5 1009.0 21.4 59 40.0 39.5 47.0 1049.0 1095.0 1100.0 1081.3 1100.0 1049.0 23.0 64 20.0 17.5 18.0 1069.0 1112.5 1118.0 1099.8 1118.0 1069.0 21.9 68 11.0 11.0 10.5 1080.0 1123.5 1128.5 1110.7 1128.5 1080.0 21.8 75 34.5 23.5 24.5 1114.5 1147.0 1153.0 1138.2 1153.0 1114.5 16.9 84 24.5 20.0 20.5 1139.0 1167.0 1173.5 1159.8 1173.5 1139.0 15.0 90 17.0 17.0 15.5 1156.0 1184.0 1189.0 1176.3 1189.0 1156.0 14.5 53 Table E - 7 Cellulose (0.55 g) with wastewater treatment residue . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 39.5 40.0 40.5 39.5 40.0 40.5 40.0 40.5 39.5 0.4 5 60.0 54.5 55.0 99.5 94.5 95.5 96.5 99.5 94.5 2.2 8 34.0 34.0 33.5 133.5 128.5 129.0 130.3 133.5 128.5 2.2 10 45.0 43.0 39.5 178.5 171.5 168.5 172.8 178.5 168.5 4.2 12 24.0 24.0 27.5 202.5 195.5 196.0 198.0 202.5 195.5 3.2 15 44.0 46.0 45.0 246.5 241.5 241.0 243.0 246.5 241.0 2.5 20 188.0 179.5 186.5 434.5 421.0 427.5 427.7 434.5 421.0 5.5 29 120.0 222.5 167.5 554.5 643.5 595.0 597.7 643.5 554.5 36.4 33 90.0 77.0 125.0 644.5 720.5 720.0 695.0 720.5 644.5 35.7 36 106.0 46.0 50.5 750.5 766.5 770.5 762.5 770.5 750.5 8.6 39 51.5 40.5 38.0 802.0 807.0 808.5 805.8 808.5 802.0 2.8 43 41.0 56.5 138.0 843.0 863.5 946.5 884.3 946.5 843.0 44.7 47 191.5 46.5 42.5 1034.5 910.0 989.0 977.8 1034.5 910.0 51.4 50 92.5 28.5 23.0 1127.0 938.5 1012.0 1025.8 1127.0 938.5 77.6 55 92.5 62.0 24.0 1219.5 1000.5 1036.0 1085.3 1219.5 1000.5 96.0 59 78.5 116.0 37.5 1298.0 1116.5 1073.5 1162.7 1298.0 1073.5 97.3 64 35.0 70.5 25.5 1333.0 1187.0 1099.0 1206.3 1333.0 1099.0 96.5 68 24.0 85.0 12.5 1357.0 1272.0 1111.5 1246.8 1357.0 1111.5 101.8 75 45.0 125.5 54.0 1402.0 1397.5 1165.5 1321.7 1402.0 1165.5 110.4 84 33.0 48.0 164.5 1435.0 1445.5 1330.0 1403.5 1445.5 1330.0 52.1 90 24.5 28.0 81.0 1459.5 1473.5 1411.0 1448.0 1473.5 1411.0 26.8 54 Table E - 8 Neat PET (3.00 g) with wastewater treatment residue . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 35.5 38.5 39.0 35.5 38.5 39.0 37.7 39.0 35.5 1.5 5 38.5 36.5 43.0 74.0 75.0 82.0 77.0 82.0 74.0 3.6 8 46.0 53.0 53.5 120.0 128.0 135.5 127.8 135.5 120.0 6.3 10 24.0 36.0 35.0 144.0 164.0 170.5 159.5 170.5 144.0 11.3 12 46.0 60.0 53.0 190.0 224.0 223.5 212.5 224.0 190.0 15.9 15 76.5 75.0 47.0 266.5 299.0 270.5 278.7 299.0 266.5 14.5 20 122.0 100.0 120.5 388.5 399.0 391.0 392.8 399.0 388.5 4.5 29 216.0 229.0 256.5 604.5 628.0 647.5 626.7 647.5 604.5 17.6 33 75.0 111.5 99.0 679.5 739.5 746.5 721.8 746.5 679.5 30.1 36 48.0 60.5 55.5 727.5 800.0 802.0 776.5 802.0 727.5 34.7 39 53.5 53.0 47.5 781.0 853.0 849.5 827.8 853.0 781.0 33.1 43 72.0 55.5 52.0 853.0 908.5 901.5 887.7 908.5 853.0 24.7 47 68.5 38.5 40.0 921.5 947.0 941.5 936.7 947.0 921.5 11.0 50 43.5 26.0 25.5 965.0 973.0 967.0 968.3 973.0 965.0 3.4 55 50.5 27.5 28.0 1015.5 1000.5 995.0 1003.7 1015.5 995.0 8.7 59 53.5 38.0 36.0 1069.0 1038.5 1031.0 1046.2 1069.0 1031.0 16.4 64 26.0 15.0 15.0 1095.0 1053.5 1046.0 1064.8 1095.0 1046.0 21.5 68 21.0 13.5 14.0 1116.0 1067.0 1060.0 1081.0 1116.0 1060.0 24.9 75 41.5 27.5 46.0 1157.5 1094.5 1106.0 1119.3 1157.5 1094.5 27.4 84 27.0 20.0 27.5 1184.5 1114.5 1133.5 1144.2 1184.5 1114.5 29.6 90 16.5 18.0 16.0 1201.0 1132.5 1149.5 1161.0 1201.0 1132.5 29.1 55 Table E - 9 PET with 1 % additive (3.00 g) with wastewater treatment residue . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 35.0 44.0 35.5 35.0 44.0 35.5 38.2 44.0 35.0 4.1 5 41.0 41.0 39.5 76.0 85.0 75.0 78.7 85.0 75.0 4.5 8 54.5 54.0 51.5 130.5 139.0 126.5 132.0 139.0 126.5 5.2 10 44.5 51.5 42.5 175.0 190.5 169.0 178.2 190.5 169.0 9.1 12 64.5 65.0 68.0 239.5 255.5 237.0 244.0 255.5 237.0 8.2 15 75.0 67.0 61.0 314.5 322.5 298.0 311.7 322.5 298.0 10.2 20 114.0 154.0 156.0 428.5 476.5 454.0 453.0 476.5 428.5 19.6 29 223.5 240.0 248.0 652.0 716.5 702.0 690.2 716.5 652.0 27.6 33 92.5 80.5 88.0 744.5 797.0 790.0 777.2 797.0 744.5 23.3 36 63.0 52.0 53.5 807.5 849.0 843.5 833.3 849.0 807.5 18.4 39 56.5 48.0 43.5 864.0 897.0 887.0 882.7 897.0 864.0 13.8 43 62.5 57.0 49.5 926.5 954.0 936.5 939.0 954.0 926.5 11.4 47 47.5 45.5 41.0 974.0 999.5 977.5 983.7 999.5 974.0 11.3 50 30.5 28.5 27.0 1004.5 1028.0 1004.5 1012.3 1028.0 1004.5 11.1 55 32.5 13.5 30.0 1037.0 1041.5 1034.5 1037.7 1041.5 1034.5 2.9 59 39.0 49.0 37.0 1076.0 1090.5 1071.5 1079.3 1090.5 1071.5 8.1 64 20.0 19.0 18.0 1096.0 1109.5 1089.5 1098.3 1109.5 1089.5 8.3 68 12.0 9.0 9.5 1108.0 1118.5 1099.0 1108.5 1118.5 1099.0 8.0 75 23.5 45.5 28.0 1131.5 1164.0 1127.0 1140.8 1164.0 1127.0 16.5 84 20.0 38.0 24.0 1151.5 1202.0 1151.0 1168.2 1202.0 1151.0 23.9 90 14.5 27.0 20.0 1166.0 1229.0 1171.0 1188.7 1229.0 1166.0 28.6 56 Table E - 10 PET with 5 % additive (3.00 g) with wastewater treatment residue . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 36.5 38.0 36.5 36.5 38.0 36.5 37.0 38.0 36.5 0.7 5 37.0 38.5 38.0 73.5 76.5 74.5 74.8 76.5 73.5 1.2 8 49.5 43.0 50.5 123.0 119.5 125.0 122.5 125.0 119.5 2.3 10 43.5 40.0 39.5 166.5 159.5 164.5 163.5 166.5 159.5 2.9 12 61.0 60.0 61.0 227.5 219.5 225.5 224.2 227.5 219.5 3.4 15 70.0 75.0 71.0 297.5 294.5 296.5 296.2 297.5 294.5 1.2 20 141.0 120.5 132.0 438.5 415.0 428.5 427.3 438.5 415.0 9.6 29 275.0 265.0 263.0 713.5 680.0 691.5 695.0 713.5 680.0 13.9 33 82.0 111.0 95.5 795.5 791.0 787.0 791.2 795.5 787.0 3.5 36 48.0 71.0 60.5 843.5 862.0 847.5 851.0 862.0 843.5 7.9 39 40.0 62.5 55.5 883.5 924.5 903.0 903.7 924.5 883.5 16.7 43 39.0 66.0 56.5 922.5 990.5 959.5 957.5 990.5 922.5 27.8 47 30.0 48.5 44.5 952.5 1039.0 1004.0 998.5 1039.0 952.5 35.5 50 18.5 28.5 22.0 971.0 1067.5 1026.0 1021.5 1067.5 971.0 39.5 55 22.0 31.5 29.5 993.0 1099.0 1055.5 1049.2 1099.0 993.0 43.5 59 31.0 39.0 36.5 1024.0 1138.0 1092.0 1084.7 1138.0 1024.0 46.8 64 12.0 18.0 17.5 1036.0 1156.0 1109.5 1100.5 1156.0 1036.0 49.4 68 6.0 10.0 11.5 1042.0 1166.0 1121.0 1109.7 1166.0 1042.0 51.3 75 22.5 22.0 21.0 1064.5 1188.0 1142.0 1131.5 1188.0 1064.5 51.0 84 23.5 18.5 21.5 1088.0 1206.5 1163.5 1152.7 1206.5 1088.0 49.0 90 18.0 14.0 20.0 1106.0 1220.5 1183.5 1170.0 1220.5 1106.0 47.7 57 Table E - 11 Blank (only manure) with anaerobic digester . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 35.0 36.5 34.0 35.0 36.5 34.0 35.2 36.5 34.0 1.0 5 28.0 26.5 27.0 63.0 63.0 61.0 62.3 63.0 61.0 0.9 8 23.0 29.5 25.0 86.0 92.5 86.0 88.2 92.5 86.0 3.1 10 18.5 15.0 14.0 104.5 107.5 100.0 104.0 107.5 100.0 3.1 12 20.0 21.0 20.0 124.5 128.5 120.0 124.3 128.5 120.0 3.5 15 24.0 27.5 26.0 148.5 156.0 146.0 150.2 156.0 146.0 4.2 20 50.0 39.0 40.5 198.5 195.0 186.5 193.3 198.5 186.5 5.0 29 219.5 261.5 211.5 418.0 456.5 398.0 424.2 456.5 398.0 24.3 33 141.5 124.5 152.5 559.5 581.0 550.5 563.7 581.0 550.5 12.8 36 131.5 124.0 178.5 691.0 705.0 729.0 708.3 729.0 691.0 15.7 39 57.0 85.0 131.5 748.0 790.0 860.5 799.5 860.5 748.0 46.4 43 53.5 56.0 101.5 801.5 846.0 962.0 869.8 962.0 801.5 67.7 47 42.0 62.0 68.5 843.5 908.0 1030.5 927.3 1030.5 843.5 77.6 50 30.5 50.5 37.0 874.0 958.5 1067.5 966.7 1067.5 874.0 79.2 55 52.0 58.5 41.5 926.0 1017.0 1109.0 1017.3 1109.0 926.0 74.7 59 59.0 51.0 42.0 985.0 1068.0 1151.0 1068.0 1151.0 985.0 67.8 64 37.0 29.0 23.0 1022.0 1097.0 1174.0 1097.7 1174.0 1022.0 62.1 68 30.0 22.5 16.0 1052.0 1119.5 1190.0 1120.5 1190.0 1052.0 56.3 75 50.0 40.5 27.0 1102.0 1160.0 1217.0 1159.7 1217.0 1102.0 46.9 84 44.5 33.5 34.5 1146.5 1193.5 1251.5 1197.2 1251.5 1146.5 42.9 90 32.0 26.5 30.0 1178.5 1220.0 1281.5 1226.7 1281.5 1178.5 42.3 58 Table E - 12 Cellulose (0.55 g) with anaerobic digester . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 37.0 36.0 40.5 37.0 36.0 40.5 37.8 40.5 36.0 1.9 5 38.5 43.0 41.0 75.5 79.0 81.5 78.7 81.5 75.5 2.5 8 44.0 39.5 45.0 119.5 118.5 126.5 121.5 126.5 118.5 3.6 10 39.0 62.5 34.0 158.5 181.0 160.5 166.7 181.0 158.5 10.2 12 13.0 13.0 38.0 171.5 194.0 198.5 188.0 198.5 171.5 11.8 15 48.0 18.5 39.5 219.5 212.5 238.0 223.3 238.0 212.5 10.8 20 35.0 19.0 23.0 254.5 231.5 261.0 249.0 261.0 231.5 12.7 29 190.0 247.0 254.0 444.5 478.5 515.0 479.3 515.0 444.5 28.8 33 122.0 125.0 94.0 566.5 603.5 609.0 593.0 609.0 566.5 18.9 36 55.0 46.5 54.5 621.5 650.0 663.5 645.0 663.5 621.5 17.5 39 43.5 44.5 51.5 665.0 694.5 715.0 691.5 715.0 665.0 20.5 43 130.0 94.0 145.0 795.0 788.5 860.0 814.5 860.0 788.5 32.3 47 181.0 175.0 170.5 976.0 963.5 1030.5 990.0 1030.5 963.5 29.1 50 88.5 134.0 100.0 1064.5 1097.5 1130.5 1097.5 1130.5 1064.5 26.9 55 85.0 141.5 88.0 1149.5 1239.0 1218.5 1202.3 1239.0 1149.5 38.3 59 61.0 58.0 69.0 1210.5 1297.0 1287.5 1265.0 1297.0 1210.5 38.7 64 20.5 23.5 29.0 1231.0 1320.5 1316.5 1289.3 1320.5 1231.0 41.3 68 13.5 16.5 28.0 1244.5 1337.0 1344.5 1308.7 1344.5 1244.5 45.5 75 43.5 48.5 43.5 1288.0 1385.5 1388.0 1353.8 1388.0 1288.0 46.6 84 44.0 36.0 38.5 1332.0 1421.5 1426.5 1393.3 1426.5 1332.0 43.4 90 32.0 20.0 24.5 1364.0 1441.5 1451.0 1418.8 1451.0 1364.0 39.0 59 Table E - 13 Neat PET (3.00 g) with anaerobic digester . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 37.0 37.5 35.5 37.0 37.5 35.5 36.7 37.5 35.5 0.8 5 30.0 33.0 31.5 67.0 70.5 67.0 68.2 70.5 67.0 1.6 8 25.0 23.0 25.0 92.0 93.5 92.0 92.5 93.5 92.0 0.7 10 16.0 15.0 13.0 108.0 108.5 105.0 107.2 108.5 105.0 1.5 12 18.5 21.5 17.5 126.5 130.0 122.5 126.3 130.0 122.5 3.1 15 22.0 25.5 25.0 148.5 155.5 147.5 150.5 155.5 147.5 3.6 20 38.5 45.0 45.5 187.0 200.5 193.0 193.5 200.5 187.0 5.5 29 220.5 216.0 219.0 407.5 416.5 412.0 412.0 416.5 407.5 3.7 33 188.0 166.0 188.0 595.5 582.5 600.0 592.7 600.0 582.5 7.4 36 173.0 167.0 160.5 768.5 749.5 760.5 759.5 768.5 749.5 7.8 39 103.0 131.0 90.5 871.5 880.5 851.0 867.7 880.5 851.0 12.3 43 69.5 83.5 84.0 941.0 964.0 935.0 946.7 964.0 935.0 12.5 47 54.5 61.0 66.5 995.5 1025.0 1001.5 1007.3 1025.0 995.5 12.7 50 30.5 36.5 38.5 1026.0 1061.5 1040.0 1042.5 1061.5 1026.0 14.6 55 32.5 38.0 41.0 1058.5 1099.5 1081.0 1079.7 1099.5 1058.5 16.8 59 38.5 42.0 49.0 1097.0 1141.5 1130.0 1122.8 1141.5 1097.0 18.9 64 22.5 24.5 26.0 1119.5 1166.0 1156.0 1147.2 1166.0 1119.5 20.0 68 21.0 17.0 16.5 1140.5 1183.0 1172.5 1165.3 1183.0 1140.5 18.1 75 70.0 26.0 34.0 1210.5 1209.0 1206.5 1208.7 1210.5 1206.5 1.6 84 58.0 23.5 31.5 1268.5 1232.5 1238.0 1246.3 1268.5 1232.5 15.8 90 36.0 22.5 22.0 1304.5 1255.0 1260.0 1273.2 1304.5 1255.0 22.2 60 Table E - 14 PET with 1 % additive (3.00 g) with anaerobic digester . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 43.0 46.5 40.5 43.0 46.5 40.5 43.3 46.5 40.5 2.5 5 28.5 30.0 30.0 71.5 76.5 70.5 72.8 76.5 70.5 2.6 8 24.5 28.0 26.5 96.0 104.5 97.0 99.2 104.5 96.0 3.8 10 17.0 18.0 17.5 113.0 122.5 114.5 116.7 122.5 113.0 4.2 12 20.0 26.5 20.0 133.0 149.0 134.5 138.8 149.0 133.0 7.2 15 26.0 37.0 26.0 159.0 186.0 160.5 168.5 186.0 159.0 12.4 20 36.0 52.5 44.0 195.0 238.5 204.5 212.7 238.5 195.0 18.7 29 212.5 196.5 188.0 407.5 435.0 392.5 411.7 435.0 392.5 17.6 33 126.0 166.0 170.0 533.5 601.0 562.5 565.7 601.0 533.5 27.6 36 154.0 141.5 175.0 687.5 742.5 737.5 722.5 742.5 687.5 24.8 39 159.0 57.0 93.0 846.5 799.5 830.5 825.5 846.5 799.5 19.5 43 95.0 58.0 97.5 941.5 857.5 928.0 909.0 941.5 857.5 36.8 47 70.0 47.5 71.0 1011.5 905.0 999.0 971.8 1011.5 905.0 47.5 50 41.5 33.5 39.5 1053.0 938.5 1038.5 1010.0 1053.0 938.5 50.9 55 39.0 43.0 42.0 1092.0 981.5 1080.5 1051.3 1092.0 981.5 49.6 59 39.5 49.5 45.0 1131.5 1031.0 1125.5 1096.0 1131.5 1031.0 46.0 64 23.0 28.5 24.0 1154.5 1059.5 1149.5 1121.2 1154.5 1059.5 43.7 68 15.0 23.0 11.5 1169.5 1082.5 1161.0 1137.7 1169.5 1082.5 39.2 75 30.0 31.5 57.0 1199.5 1114.0 1218.0 1177.2 1218.0 1114.0 45.3 84 31.0 65.0 29.5 1230.5 1179.0 1247.5 1219.0 1247.5 1179.0 29.1 90 32.5 40.0 25.5 1263.0 1219.0 1273.0 1251.7 1273.0 1219.0 23.5 61 Table E - 15 PET with 5 % additive (3.00 g) with anaerobic digester . Measured gas volume ( mL ) Cumulative gas volume ( mL ) Day 1 2 3 1 2 3 Average Max Min Standard deviation 3 35.5 39.5 46.5 35.5 39.5 46.5 40.5 46.5 35.5 4.5 5 30.0 29.5 32.0 65.5 69.0 78.5 71.0 78.5 65.5 5.5 8 21.0 24.0 21.0 86.5 93.0 99.5 93.0 99.5 86.5 5.3 10 12.0 12.0 11.0 98.5 105.0 110.5 104.7 110.5 98.5 4.9 12 21.0 19.0 19.0 119.5 124.0 129.5 124.3 129.5 119.5 4.1 15 27.0 23.0 26.0 146.5 147.0 155.5 149.7 155.5 146.5 4.1 20 44.0 49.5 51.5 190.5 196.5 207.0 198.0 207.0 190.5 6.8 29 225.5 232.5 235.5 416.0 429.0 442.5 429.2 442.5 416.0 10.8 33 134.5 129.0 173.5 550.5 558.0 616.0 574.8 616.0 550.5 29.3 36 141.5 82.5 158.0 692.0 640.5 774.0 702.2 774.0 640.5 55.0 39 134.0 73.0 77.0 826.0 713.5 851.0 796.8 851.0 713.5 59.8 43 101.0 99.5 85.5 927.0 813.0 936.5 892.2 936.5 813.0 56.1 47 79.5 67.0 61.5 1006.5 880.0 998.0 961.5 1006.5 880.0 57.7 50 47.0 37.5 39.0 1053.5 917.5 1037.0 1002.7 1053.5 917.5 60.6 55 50.0 32.0 45.5 1103.5 949.5 1082.5 1045.2 1103.5 949.5 68.2 59 49.5 41.0 50.5 1153.0 990.5 1133.0 1092.2 1153.0 990.5 72.4 64 26.0 25.5 23.0 1179.0 1016.0 1156.0 1117.0 1179.0 1016.0 72.0 68 18.0 20.5 13.5 1197.0 1036.5 1169.5 1134.3 1197.0 1036.5 70.1 75 35.0 34.0 27.5 1232.0 1070.5 1197.0 1166.5 1232.0 1070.5 69.4 84 35.0 36.0 35.0 1267.0 1106.5 1232.0 1201.8 1267.0 1106.5 68.9 90 29.0 20.0 27.0 1296.0 1126.5 1259.0 1227.2 1296.0 1126.5 72.8 62 APPENDIX F: Original biodegradation extent data of each bioreactor Table F - 1 Cellulose (0.55 g) with landfill leachate . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 - 0.1 - 0.2 0.2 0.0 0.2 - 0.2 0.2 5 2.0 1.8 2.0 2.0 2.0 1.8 0.1 8 2.8 2.8 2.6 2.8 2.8 2.6 0.1 10 4.5 6.0 4.4 4.9 6.0 4.4 0.7 12 14.4 3.8 11.2 9.8 14.4 3.8 4.4 15 17.3 10.9 13.2 13.8 17.3 10.9 2.7 20 11.2 9.7 8.3 9.7 11.2 8.3 1.2 29 19.0 17.9 12.3 16.4 19.0 12.3 2.9 33 29.1 16.2 19.7 21.7 29.1 16.2 5.4 36 35.8 11.1 28.8 25.2 35.8 11.1 10.4 39 46.2 7.0 35.4 29.5 46.2 7.0 16.5 43 48.0 2.1 33.4 27.8 48.0 2.1 19.2 47 44.1 - 3.3 25.3 22.0 44.1 - 3.3 19.5 50 43.7 0.7 19.5 21.3 43.7 0.7 17.6 55 40.2 14.2 13.5 22.6 40.2 13.5 12.4 59 36.7 15.4 13.1 21.7 36.7 13.1 10.6 64 30.8 12.7 8.1 17.2 30.8 8.1 9.8 68 24.0 10.4 1.1 11.9 24.0 1.1 9.4 75 14.6 24.7 0.8 13.4 24.7 0.8 9.8 84 16.5 32.4 33.5 27.5 33.5 16.5 7.8 90 22.2 35.1 39.8 32.4 39.8 22.2 7.4 63 Table F - 2 Neat PET (3.00 g) with landfill leachate . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.0 0.0 0.1 0.1 0.1 0.0 0.0 5 0.0 0.0 0.1 0.0 0.1 0.0 0.1 8 - 0.1 - 0.1 0.0 - 0.1 0.0 - 0.1 0.0 10 - 0.2 - 0.1 - 0.1 - 0.2 - 0.1 - 0.2 0.0 12 - 0.3 - 0.2 - 0.1 - 0.2 - 0.1 - 0.3 0.1 15 - 0.3 - 0.3 0.0 - 0.2 0.0 - 0.3 0.1 20 - 0.5 - 0.6 2.1 0.3 2.1 - 0.6 1.2 29 - 0.2 0.0 1.3 0.4 1.3 - 0.2 0.7 33 - 0.1 0.4 1.5 0.6 1.5 - 0.1 0.7 36 0.2 0.9 1.1 0.7 1.1 0.2 0.3 39 0.1 0.8 0.7 0.5 0.8 0.1 0.3 43 0.0 0.6 0.1 0.3 0.6 0.0 0.2 47 - 0.8 - 0.4 - 0.9 - 0.7 - 0.4 - 0.9 0.2 50 - 1.0 - 0.8 - 1.3 - 1.0 - 0.8 - 1.3 0.2 55 0.2 0.6 - 1.9 - 0.4 0.6 - 1.9 1.1 59 1.3 1.4 - 2.3 0.1 1.4 - 2.3 1.7 64 1.8 1.0 - 3.1 - 0.1 1.8 - 3.1 2.1 68 1.7 0.2 - 3.9 - 0.7 1.7 - 3.9 2.4 75 1.0 - 0.8 - 4.7 - 1.5 1.0 - 4.7 2.4 84 1.1 0.2 - 4.3 - 1.0 1.1 - 4.3 2.4 90 1.0 1.0 - 2.1 0.0 1.0 - 2.1 1.4 64 Table F - 3 PET with 1 % additive (3.00 g) with landfill leachate . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.1 0.1 0.1 0.1 0.1 0.1 0.0 5 0.0 0.0 0.1 0.1 0.1 0.0 0.0 8 - 0.1 - 0.1 0.1 0.0 0.1 - 0.1 0.1 10 - 0.1 - 0.2 0.2 0.0 0.2 - 0.2 0.1 12 - 0.1 - 0.3 0.1 - 0.1 0.1 - 0.3 0.2 15 - 0.1 - 0.3 0.0 - 0.1 0.0 - 0.3 0.1 20 - 0.4 - 0.3 - 0.4 - 0.4 - 0.3 - 0.4 0.0 29 - 0.3 - 0.1 0.2 - 0.1 0.2 - 0.3 0.2 33 0.6 0.9 0.3 0.6 0.9 0.3 0.3 36 1.8 2.7 0.8 1.8 2.7 0.8 0.8 39 1.9 4.0 0.9 2.3 4.0 0.9 1.3 43 1.4 5.1 1.5 2.6 5.1 1.4 1.7 47 0.1 5.2 2.2 2.5 5.2 0.1 2.1 50 - 0.6 5.2 2.6 2.4 5.2 - 0.6 2.4 55 - 1.7 4.8 2.9 2.0 4.8 - 1.7 2.7 59 - 2.2 4.6 3.0 1.8 4.6 - 2.2 2.9 64 - 2.1 4.1 2.6 1.5 4.1 - 2.1 2.7 68 - 1.9 3.4 1.7 1.1 3.4 - 1.9 2.2 75 - 1.4 2.4 0.4 0.4 2.4 - 1.4 1.5 84 - 0.9 2.1 0.0 0.4 2.1 - 0.9 1.2 90 - 0.8 1.7 - 0.4 0.2 1.7 - 0.8 1.1 65 Table F - 4 PET with 5 % additive (3.00 g) with landfill leachate . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.1 0.1 0.1 0.1 0.1 0.1 0.0 5 0.0 0.1 0.1 0.1 0.1 0.0 0.0 8 0.0 0.1 0.0 0.0 0.1 0.0 0.1 10 - 0.1 0.0 0.0 0.0 0.0 - 0.1 0.0 12 - 0.2 - 0.1 0.0 - 0.1 0.0 - 0.2 0.1 15 - 0.2 - 0.1 - 0.1 - 0.1 - 0.1 - 0.2 0.0 20 - 0.3 - 0.1 - 0.3 - 0.2 - 0.1 - 0.3 0.1 29 - 0.1 - 0.1 0.5 0.1 0.5 - 0.1 0.3 33 1.1 0.8 1.0 0.9 1.1 0.8 0.1 36 2.7 1.4 0.7 1.6 2.7 0.7 0.8 39 3.9 2.4 0.5 2.2 3.9 0.5 1.4 43 4.6 3.4 1.4 3.2 4.6 1.4 1.3 47 4.4 3.6 2.5 3.5 4.4 2.5 0.8 50 4.4 3.8 3.3 3.9 4.4 3.3 0.4 55 4.2 3.7 3.7 3.8 4.2 3.7 0.2 59 4.2 3.7 3.6 3.8 4.2 3.6 0.2 64 3.8 3.3 3.1 3.4 3.8 3.1 0.3 68 3.2 2.7 2.3 2.7 3.2 2.3 0.3 75 2.1 1.6 0.9 1.6 2.1 0.9 0.5 84 2.3 1.4 0.9 1.5 2.3 0.9 0.6 90 2.1 1.1 0.7 1.3 2.1 0.7 0.6 66 Table F - 5 Cellulose (0.55 g) with wastewater treatment residue . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 1.1 1.2 1.3 1.2 1.3 1.1 0.1 5 5.4 4.5 4.6 4.8 5.4 4.5 0.4 8 3.0 2.1 2.2 2.4 3.0 2.1 0.4 10 4.5 3.2 2.6 3.4 4.5 2.6 0.8 12 - 0.9 - 2.3 - 2.2 - 1.8 - 0.9 - 2.3 0.6 15 - 7.1 - 8.0 - 8.1 - 7.7 - 7.1 - 8.1 0.5 20 5.7 3.1 4.4 4.4 5.7 3.1 1.0 29 - 16.6 0.3 - 8.9 - 8.4 0.3 - 16.6 6.9 33 - 20.3 - 5.9 - 6.0 - 10.7 - 5.9 - 20.3 6.8 36 - 12.0 - 8.9 - 8.2 - 9.7 - 8.2 - 12.0 1.6 39 - 13.5 - 12.6 - 12.3 - 12.8 - 12.3 - 13.5 0.5 43 - 17.3 - 13.4 2.4 - 9.4 2.4 - 17.3 8.5 47 9.9 - 13.7 1.3 - 0.8 9.9 - 13.7 9.8 50 22.1 - 13.6 0.3 2.9 22.1 - 13.6 14.7 55 34.2 - 7.3 - 0.6 8.8 34.2 - 7.3 18.2 59 41.1 6.7 - 1.5 15.4 41.1 - 1.5 18.5 64 44.2 16.5 - 0.2 20.2 44.2 - 0.2 18.3 68 46.7 30.6 0.2 25.8 46.7 0.2 19.3 75 50.1 49.2 5.2 34.8 50.1 5.2 21.0 84 52.2 54.2 32.3 46.2 54.2 32.3 9.9 90 53.7 56.4 44.5 51.6 56.4 44.5 5.1 67 Table F - 6 Neat PET (3.00 g) with wastewater treatment residue . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.0 0.1 0.1 0.1 0.1 0.0 0.0 5 0.1 0.1 0.3 0.1 0.3 0.1 0.1 8 0.1 0.3 0.4 0.2 0.4 0.1 0.2 10 - 0.3 0.2 0.4 0.1 0.4 - 0.3 0.3 12 - 0.4 0.4 0.4 0.1 0.4 - 0.4 0.4 15 - 0.4 0.4 - 0.3 - 0.1 0.4 - 0.4 0.4 20 - 0.4 - 0.1 - 0.3 - 0.3 - 0.1 - 0.4 0.1 29 - 0.9 - 0.3 0.1 - 0.4 0.1 - 0.9 0.4 33 - 1.7 - 0.3 - 0.1 - 0.7 - 0.1 - 1.7 0.7 36 - 2.1 - 0.3 - 0.3 - 0.9 - 0.3 - 2.1 0.8 39 - 2.2 - 0.5 - 0.6 - 1.1 - 0.5 - 2.2 0.8 43 - 2.0 - 0.6 - 0.8 - 1.1 - 0.6 - 2.0 0.6 47 - 1.5 - 0.9 - 1.0 - 1.1 - 0.9 - 1.5 0.3 50 - 1.1 - 0.9 - 1.1 - 1.0 - 0.9 - 1.1 0.1 55 - 0.6 - 0.9 - 1.1 - 0.9 - 0.6 - 1.1 0.2 59 - 0.3 - 1.0 - 1.2 - 0.9 - 0.3 - 1.2 0.4 64 - 0.1 - 1.1 - 1.3 - 0.8 - 0.1 - 1.3 0.5 68 0.1 - 1.1 - 1.2 - 0.7 0.1 - 1.2 0.6 75 0.5 - 1.1 - 0.8 - 0.5 0.5 - 1.1 0.7 84 0.6 - 1.1 - 0.6 - 0.4 0.6 - 1.1 0.7 90 0.6 - 1.1 - 0.7 - 0.4 0.6 - 1.1 0.7 68 Table F - 7 PET w ith 1 % additive (3.00 g) with wastewater treatment residue . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.0 0.3 0.0 0.1 0.3 0.0 0.1 5 0.1 0.3 0.1 0.2 0.3 0.1 0.1 8 0.3 0.5 0.2 0.3 0.5 0.2 0.1 10 0.5 0.9 0.3 0.6 0.9 0.3 0.2 12 0.8 1.2 0.7 0.9 1.2 0.7 0.2 15 0.7 0.9 0.3 0.7 0.9 0.3 0.2 20 0.6 1.7 1.2 1.2 1.7 0.6 0.5 29 0.2 1.8 1.5 1.2 1.8 0.2 0.7 33 - 0.2 1.1 0.9 0.6 1.1 - 0.2 0.6 36 - 0.1 0.9 0.7 0.5 0.9 - 0.1 0.4 39 - 0.2 0.6 0.3 0.2 0.6 - 0.2 0.3 43 - 0.2 0.5 0.1 0.1 0.5 - 0.2 0.3 47 - 0.2 0.4 - 0.1 0.0 0.4 - 0.2 0.3 50 - 0.1 0.4 - 0.1 0.0 0.4 - 0.1 0.3 55 - 0.1 0.1 - 0.1 0.0 0.1 - 0.1 0.1 59 - 0.1 0.2 - 0.2 0.0 0.2 - 0.2 0.2 64 - 0.1 0.2 - 0.3 0.0 0.2 - 0.3 0.2 68 - 0.1 0.2 - 0.3 - 0.1 0.2 - 0.3 0.2 75 - 0.2 0.6 - 0.3 0.1 0.6 - 0.3 0.4 84 - 0.2 1.0 - 0.2 0.2 1.0 - 0.2 0.6 90 - 0.3 1.3 - 0.1 0.3 1.3 - 0.3 0.7 69 Table F - 8 PET with 5 % additive (3.00 g) with wastewater treatment residue . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.1 0.1 0.1 0.1 0.1 0.1 0.0 5 0.1 0.1 0.1 0.1 0.1 0.1 0.0 8 0.1 0.0 0.2 0.1 0.2 0.0 0.1 10 0.3 0.1 0.2 0.2 0.3 0.1 0.1 12 0.5 0.3 0.4 0.4 0.5 0.3 0.1 15 0.3 0.3 0.3 0.3 0.3 0.3 0.0 20 0.8 0.3 0.6 0.6 0.8 0.3 0.2 29 1.7 0.9 1.2 1.3 1.7 0.9 0.3 33 1.1 1.0 0.9 1.0 1.1 0.9 0.1 36 0.7 1.2 0.8 0.9 1.2 0.7 0.2 39 0.3 1.2 0.7 0.7 1.2 0.3 0.4 43 - 0.3 1.4 0.6 0.6 1.4 - 0.3 0.7 47 - 0.7 1.4 0.5 0.4 1.4 - 0.7 0.9 50 - 1.0 1.4 0.4 0.3 1.4 - 1.0 1.0 55 - 1.1 1.4 0.4 0.2 1.4 - 1.1 1.1 59 - 1.4 1.4 0.3 0.1 1.4 - 1.4 1.1 64 - 1.5 1.4 0.2 0.0 1.4 - 1.5 1.2 68 - 1.7 1.3 0.3 0.0 1.3 - 1.7 1.2 75 - 1.8 1.2 0.1 - 0.2 1.2 - 1.8 1.2 84 - 1.7 1.1 0.1 - 0.2 1.1 - 1.7 1.2 90 - 1.7 1.1 0.2 - 0.2 1.1 - 1.7 1.2 70 Table F - 9 Cellulose (0.55 g) with anaerobic digester . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.3 0.2 1.0 0.5 1.0 0.2 0.4 5 2.5 3.2 3.6 3.1 3.6 2.5 0.5 8 5.9 5.8 7.3 6.3 7.3 5.8 0.7 10 10.3 14.6 10.7 11.9 14.6 10.3 1.9 12 9.0 13.2 14.1 12.1 14.1 9.0 2.2 15 13.2 11.8 16.7 13.9 16.7 11.8 2.0 20 11.6 7.2 12.8 10.6 12.8 7.2 2.4 29 3.9 10.3 17.2 10.5 17.2 3.9 5.5 33 0.5 7.6 8.6 5.6 8.6 0.5 3.6 36 - 16.5 - 11.1 - 8.5 - 12.0 - 8.5 - 16.5 3.3 39 - 25.5 - 19.9 - 16.0 - 20.5 - 16.0 - 25.5 3.9 43 - 14.2 - 15.4 - 1.9 - 10.5 - 1.9 - 15.4 6.1 47 9.2 6.9 19.6 11.9 19.6 6.9 5.5 50 18.6 24.8 31.1 24.8 31.1 18.6 5.1 55 25.1 42.1 38.2 35.1 42.1 25.1 7.3 59 27.0 43.5 41.7 37.4 43.5 27.0 7.3 64 25.3 42.3 41.5 36.4 42.3 25.3 7.8 68 23.5 41.1 42.5 35.7 42.5 23.5 8.6 75 24.4 42.9 43.3 36.8 43.3 24.4 8.8 84 25.6 42.6 43.5 37.2 43.5 25.6 8.2 90 26.1 40.8 42.6 36.5 42.6 26.1 7.4 71 Table F - 10 Neat PET (3.00 g) with anaerobic digester . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.0 0.1 0.0 0.0 0.1 0.0 0.0 5 0.1 0.2 0.1 0.1 0.2 0.1 0.0 8 0.1 0.1 0.1 0.1 0.1 0.1 0.0 10 0.1 0.1 0.0 0.1 0.1 0.0 0.0 12 0.1 0.1 0.0 0.0 0.1 0.0 0.1 15 0.0 0.1 - 0.1 0.0 0.1 - 0.1 0.1 20 - 0.2 0.2 0.0 0.0 0.2 - 0.2 0.1 29 - 0.4 - 0.2 - 0.3 - 0.3 - 0.2 - 0.4 0.1 33 0.8 0.5 0.9 0.7 0.9 0.5 0.2 36 1.5 1.0 1.3 1.2 1.5 1.0 0.2 39 1.7 2.0 1.3 1.7 2.0 1.3 0.3 43 1.7 2.3 1.6 1.9 2.3 1.6 0.3 47 1.7 2.4 1.8 1.9 2.4 1.7 0.3 50 1.4 2.3 1.8 1.8 2.3 1.4 0.4 55 1.0 2.0 1.5 1.5 2.0 1.0 0.4 59 0.7 1.8 1.5 1.3 1.8 0.7 0.5 64 0.5 1.7 1.4 1.2 1.7 0.5 0.5 68 0.5 1.5 1.3 1.1 1.5 0.5 0.4 75 1.2 1.2 1.1 1.2 1.2 1.1 0.0 84 1.7 0.9 1.0 1.2 1.7 0.9 0.4 90 1.9 0.7 0.8 1.1 1.9 0.7 0.5 72 Table F - 11 PET with 1 % additive (3.00 g) with anaerobic digester . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.2 0.3 0.1 0.2 0.3 0.1 0.1 5 0.2 0.3 0.2 0.3 0.3 0.2 0.1 8 0.2 0.4 0.2 0.3 0.4 0.2 0.1 10 0.2 0.4 0.3 0.3 0.4 0.2 0.1 12 0.2 0.6 0.2 0.4 0.6 0.2 0.2 15 0.2 0.9 0.3 0.4 0.9 0.2 0.3 20 0.0 1.1 0.3 0.5 1.1 0.0 0.5 29 - 0.4 0.3 - 0.8 - 0.3 0.3 - 0.8 0.4 33 - 0.7 0.9 0.0 0.0 0.9 - 0.7 0.7 36 - 0.5 0.8 0.7 0.3 0.8 - 0.5 0.6 39 1.1 0.0 0.8 0.6 1.1 0.0 0.5 43 1.7 - 0.3 1.4 0.9 1.7 - 0.3 0.9 47 2.0 - 0.5 1.7 1.1 2.0 - 0.5 1.2 50 2.1 - 0.7 1.7 1.0 2.1 - 0.7 1.2 55 1.8 - 0.9 1.5 0.8 1.8 - 0.9 1.2 59 1.5 - 0.9 1.4 0.7 1.5 - 0.9 1.1 64 1.4 - 0.9 1.3 0.6 1.4 - 0.9 1.1 68 1.2 - 0.9 1.0 0.4 1.2 - 0.9 0.9 75 1.0 - 1.1 1.4 0.4 1.4 - 1.1 1.1 84 0.8 - 0.4 1.2 0.5 1.2 - 0.4 0.7 90 0.9 - 0.2 1.1 0.6 1.1 - 0.2 0.6 73 Table F - 12 PET with 5 % additive (3.00 g) with anaerobic digester . Biodegradation extent (%) Day 1 2 3 Average Max Min Standard deviation 3 0.0 0.1 0.3 0.1 0.3 0.0 0.1 5 0.1 0.2 0.4 0.2 0.4 0.1 0.1 8 0.0 0.1 0.3 0.1 0.3 0.0 0.1 10 - 0.1 0.0 0.2 0.0 0.2 - 0.1 0.1 12 - 0.1 0.0 0.1 0.0 0.1 - 0.1 0.1 15 - 0.1 - 0.1 0.1 0.0 0.1 - 0.1 0.1 20 - 0.1 0.1 0.3 0.1 0.3 - 0.1 0.2 29 - 0.2 0.1 0.4 0.1 0.4 - 0.2 0.3 33 - 0.3 - 0.1 1.3 0.3 1.3 - 0.3 0.7 36 - 0.4 - 1.6 1.6 - 0.1 1.6 - 1.6 1.3 39 0.6 - 2.1 1.2 - 0.1 1.2 - 2.1 1.4 43 1.4 - 1.4 1.6 0.5 1.6 - 1.4 1.4 47 1.9 - 1.1 1.7 0.8 1.9 - 1.1 1.4 50 2.1 - 1.2 1.7 0.9 2.1 - 1.2 1.5 55 2.1 - 1.6 1.6 0.7 2.1 - 1.6 1.7 59 2.1 - 1.9 1.6 0.6 2.1 - 1.9 1.8 64 2.0 - 2.0 1.4 0.5 2.0 - 2.0 1.7 68 1.9 - 2.0 1.2 0.3 1.9 - 2.0 1.7 75 1.8 - 2.2 0.9 0.2 1.8 - 2.2 1.7 84 1.7 - 2.2 0.8 0.1 1.7 - 2.2 1.7 90 1.7 - 2.4 0.8 0.0 1.7 - 2.4 1.8 74 BIBLIOGRAPHY 75 BIBLIOGRAPHY [1] EPA , " Municipal Solid Waste Generation, Recycling, and Disposal in the United States Tables and Figures for 201 2 U.S . " Accessed Apr 2 2 , 2015. http://www.epa.gov/solidwaste/nonhaz/municipal/msw99.htm [2] Hoornweg, Daniel, and Perinaz Bhada - Tata , "What a waste: a global review of solid waste management." 2012. Accessed Apr 2 2 , 2015. http://siteresources.worldbank.org/INTURBANDEVELOPMENT/Resources/336387 - 1334852610766/What_a_Waste2012_Final.pdf [3] European Environment Agency (EEA) , "Managing Municipal Solid Waste - a Review of Achievements in 32 European Countries." Accessed Apr 2 2 , 2015. http://www.eea.europa.eu/publications/managing - municipal - solid - waste [4] PlasticsEurope , "Plastics the Facts 2012 An Analysis of European Plastics Production, Deman d and Waste Data for 2011." Accessed Apr 2 2 , 2015. http://www.plasticseurope.org/documents/document/20121120170458 - final_plasticsthefacts_nov2012_en_web_resolution.pdf [5] NAPCOR , "Postconsumer PET Container Recycling Activity in 2013." Accessed Apr 2 2 , 2015. http://www.napcor.com/pdf/NAPCOR_2013RateReport - FINAL.pdf [6] EPBP , "How to Keep a Sustainable PET Recycling Industry in Europe." Accessed Apr 2 2 , 2015. http://www.epbp.org/ [7] The Council for PET Bottle Recycling , "Recycling Rate of PET Bottles." Accessed Apr 2 2 , 2015. http://www.petbottle - rec.gr.jp/english/actual2.html [8] Selke, Susan E. M., John D. Culter, and Ruben J. Hernandez , Properties, Processing, Applications, and Regulations . 2004. [9] Chemical & Engineering News , "Coca - Cola's Biobased Bottles." Accessed Apr 02 , 2015. https://pubs.acs.org/cen/news/87/i21/8721notw9.html [10] Chemistryworld , "Coca - Cola Collaborates on Bio - PET Project." Accessed Apr 02 , 2015. http://www.rsc.org/chemistryworld/2012/06/coca - cola - collaborates - bio - pet - project [11] Passport . G lobal beverage packaging: refreshing packaging developments for sus tained growth. Jun e 2014 . [12] ASTM D883 - 12 , " Standard Terminology Relating to Plastics . " ASTM International , 20 12 . www.astm.org. 76 [13] Leejarkpai, Thanawadee, Unchalee Suwanmanee, Yosita Rudeekit, and Thumrongrut Mungcharoen. "Biodegradable kinetics of plastics under controlled composting conditions." Waste management 31, no. 6 (2011): 1153 - 1161. [14] Kijchavengkul, Thitisilp, and Rafael Auras. "Compostability of polymers." Polymer international 57, no. 6 (2008): 793 - 804. [15] Themelis , Nickolas J., and Priscilla A. Ulloa. "Methane generation in landfills." Renewable Energy 32, no. 7 (2007): 1243 - 1257. [16] Yagi, Hisaaki, Fumi Ninomiya, Masahiro Funabashi, and Masao Kunioka. "Mesophilic anaerobic biodegradation test and analysis of eubacteri a and archaea involved in anaerobic biodegradation of four specified biodegradable polyesters." Polymer Degradation and Stability 110 (2014): 278 - 283. [17] Yagi, Hisaaki, Fumi Ninomiya, Masahiro Funabashi, and Masao Kunioka. "Thermophilic anaerobic biodegradat ion test and analysis of eubacteria involved in anaerobic biodegradation of four specified biodegradable polyesters." Polymer Degradation and Stability 98, no. 6 (2013): 1182 - 1187. [18] Yagi, Hisaaki, Fumi Ninomiya, Masahiro Funabashi, and Masao Kunioka. "Anaer obic biodegradation of poly (lactic acid) film in anaerobic sludge." Journal of Polymers and the Environment 20, no. 3 (2012): 673 - 680. [19] Hubackova, Jitka, Marie Dvorackova, Petr Svoboda, Pavel Mokrejs, Jan Kupec, Iva Pozarova, Pavol Alexy, Peter Bugaj , Michal Machovsky, and Marek Koutny. "Influence of various starch types on PCL/starch blends anaerobic biodegradation." Polymer Testing 32, no. 6 (2013): 1011 - 1019. [20] "Biodegradation of was te PET based copolyesters in thermophilic anaerobic sludge." Polymer Degradation and Stability 111 (2015): 176 - 184. [21] Yam, Kit L., ed. "Landfills." The Wiley encyclopedia of packaging technology . John Wiley & Sons, 20 09 . [22] Energy Information Administration , "Documentation for Emissions of Greenhouse Gases in the United States 2006." Accessed Apr 06 , 2015. http://www.eia.gov/oiaf/1605/ggrpt/documentation/pdf/0638(2006).pdf [23] Zimring, Carl A., and William L. Rathje, eds. "Landfills, Modern." Encyclopedia of consumption and waste: the social science of garbage . Vol. 1. Sage, 2012. [24] Kumar, Sunil, Chart Chiemchaisri, and Ackmez Mudhoo. "Bioreactor landfill technology in municipal solid waste treatment: An overview." Critical reviews in biotechnology 31, no. 1 (2011): 77 - 97. [25] Freudenrich, Ph.D. "How Landfills Work." HowStuffWorks . Accessed Apr 06 , 2015. http://science.howstuffworks.com/environmental/green - science/landfill.htm 77 [26] Themelis, Nickolas J., and Young Hwan Kim. "Material and energy balances in a large - scale aer obic bioconversion cell." Waste management & research 20, no. 3 (2002): 234 - 242. [27] Ebnesajjad, Sina, ed. "Biodegradable Polymers and Polymer Blends." Handbook of biopolymers and biodegradable plastics: properties, processing and applications . William Andrew , 2012. [28] IHS P ressroom , "Consumer Pressure and Legislation Increasing Demand for Biodegradable Plastics by Nearly 15 Percent Annually During 2012 to 2017 in North America, Europe and Asia, Says IHS Study ." Accessed Apr 06 , 2015. http://press.ihs.com/press - release/bio - plastics/consumer - pressure - and - legislation - increasing - demand - biodegradable - plasti c [29] Ammala, Anne, Stuart Bateman, Katherine Dean, Eustathios Petinakis, Parveen Sangwan, Susan Wong, Qiang Yuan, Long Yu, Colin Patrick, and K. H. Leong. "An overview of degradable and biodegradable polyolefins." Progress in Polymer Science 36, no. 8 (2011): 1015 - 1049. [30] EPI , "TDPA®: Totally Degradable Plastic Additive Accessed Apr 14 , 2015. http://www.epi - global.com/en/about - tdpa.php [31] Wells Plastics Limited , "Why Reverte®?" Accessed Apr 14 , 2015. http://www.reverteplastics.com/eng/reverte.php [32] Add - X Biotech , " AddiFlex ® " Accessed Apr 14 , 2015. http://www.add - xbiotech.com/products.aspx [33] Symphony Environmental , " D 2 w Oxo - biodegradable Plastic " Accessed Apr 14 , 2015. http://www.symphonyenvironmental.com/d2w [34] P - Life Japan Inc , "P - Life" Accessed Apr 14 , 2015. http://www012.upp.so - net.ne.jp/p - lifeasia/html/gijyutuen.htm [35] Jakubowicz, Ignacy, Nazdaneh Yarahmadi, and Veronica Arthurson. "Kinetics of abiotic and bioti c degradability of low - density polyethylene containing prodegradant additives and its effect on the growth of microbial communities." Polymer Degradation and Stability 96, no. 5 (2011): 919 - 928. [36] Scoponi, Marco, Fiorella Pradella, and Vittorio Carassiti. "P hotodegradable polyolefins. Photo - oxidation mechanisms of innovative polyolefin copolymers containing double bonds." Coordination chemistry reviews 125, no. 1 (1993): 219 - 230. [37] EcoLogic , "HOW ECO - Accessed Apr 14 , 2015. http://www.ecologic - llc.com/product/how - it - works [38] BioTec Environmental , "About EcoPure®: An Organic Plastic Biodegradation Additive." Accessed Apr 14 , 2015. http://www.goecopure.com/about - us 78 [39] TekPak Solutions , " Omnidegradable Packaging " Accessed Apr 14 , 2015. http://www.tekpaksolutions.com/discovery.php [40] ENSO Plastics, "Why ENSO Biodegradable Plastics." http://www.ensoplastics.com/Products/Products.html [41] Lake, John Allen, and Samuel David Adams. CHEMICAL ADDITIVES TO MAKE POLYMERIC MATERIALS BIODE GRADABLE. BIO - TEC ENVIRONMENTAL LLC, assignee. Patent 2008 / 0103232. May 1 2008 [42] ASTM , 20 07 , " Standard Test Method for Determining the Anaerobic Biodegradation of Plastic Materials in the Presence of Municipal Sewage Sludge . " ASTM International , 20 0 7. www.astm.org . [43] ASTM D5511 12 , 20 12 , " Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials under High - Solids Anaerobic - Digestion Conditions . " ASTM International , 20 12. www.astm.org . [44] ASTM D5526 12 , 20 12 , " Standard Test Method for Determining Anaerobic . " ASTM International , 20 12. www.astm.org . [45] ASTM D7475 11 , 20 11 , " Standard Test Method for Determining the Aerobic Degradation and Anaerobic Biodegradation of Plastic Materials under Accelerated . " ASTM International , 20 11. www.astm.org . [46] ISO 13975:2012 , " Plastics -- Determination of the ultimate anaerobic biodegradation of plastic materials in controlled slurry digestion systems -- Method by measurement of biogas production . " International Organization for Standardization , 20 1 2 . www.iso.org/ [47] ISO 14853:2005 , " Plastics -- Determination of the ultimate anaerobic biodegradation of plastic materials in an aqueous system -- Method by measurement of biogas production . " International Organization for Standardization , 20 05. www.iso.org/ [48] ISO 15985:2014 , " Plastics -- Determination of the ultimate anaerobic biodegradation under high - solids anaerobic - digestion conditions -- Method by analysis of released biogas . " International Organization for Standardization , 20 14. www.iso.org/ [49] Fernández, J., M. Pérez, and L. I. Romero. "Kinetics of mesophilic anaerobic digestion of the organic fraction of municipal solid waste: influence of initial total solid concentration." Bioresource technology 101, no. 16 (2010): 6322 - 6328. [50] Chen, Ye, Jay J. Cheng, and Kurt S. Creamer. "Inhibition of anaerobic digestion process: a review." Bioresource technology 99, no. 10 (2008): 4044 - 4064. 79 [51] Shin, Hang - Sik, Kyu - Seon Yoo, and Jae K. Park. "Removal of polychlorinated phenols in sequential anaerobic aerobic biofilm reactors packed with tire chips." Water environment research 71, no. 3 (1999): 363 - 367.