3&5 WNWH‘lllllllllllltlmWIHIIHHIUIUWWI quSIS '" nunuIMinimumMinimum:uI "‘ 3 1293 10602 7398 I T? CI" i'. i..- I. 9‘ .03: «3‘ 5‘ I 6 .v.;.l This is to certify that the dissertation entitled THE FEASIBILITY OF PRODUCING ETHANOL 'FROM POTATO PROCESSING WASTE presented by PAO-JUI DAVID HUANG has been accepted towards fulfillment of the requirements for 1 PhD degree in Food Sc ence ajor professor 01W 4/. Qu/ / Date May 25, 1982 MS U is an Affirmative Action/Equal Opportunity Institution 0-12771 '_' _'—_’-—h :ijggir‘b駥§L67 '5' MSU LIBRARIES .—;_. RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is refyrned after the date stamged below. 7% 031:9 SB lion JAN 0 61993 THE FEASIBILITY OF PRODUCING ETHANOL FROM POTATO PROCESSING WASTE By Pao—jui David Huang A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Food Science & Human Nutrition 1982 ABSTRACT THE FEASIBILITY 0F PRODUCING ETHANOL FROM POTATO PROCESSING WASTES BY Pao-jui David Huang The potato processing industry generates several hundred thousand pounds of potato waste each day. Since the United States has an energy crisis, and an excess of potato processing waste, there should be opportunities for an economical conversion of potato starch to ethanol which could supply a source of energy while lowering the cost of disposal. The amounts and compositional characteristics of solid waste streams from 9 different unit Operations in a small scale potato processing industry were examined. This study indicates an average of 36.7 percent (w/w) of total incoming raw material was lost in this small potato processing plant. The potato procesing waste (PPW ; 59.3 percent of total waste and approximately 76 percent of total starch) in the final hopper was used as the feedstock in the production of ethanol by fermentation. Thermostable commercial enzymes, TAKA-THERM and Diazyme L-lOO were used to convert starch and polysaccharides in waste to monosaccharides. The completely converted potato processing waste contained 13 to 16 percent fermentable sugar, and the final ethanol concentration of 7.8 to 9 percent (v/v) was produced by Red Star DADY (distiller's active dry yeast). The results from the batch system indicate that the continuous system should have potential as an efficient process of converting potato processing waste to ethanol. 0n continuous fermentation, 1.28 ml of pure anhydrous ethanol were produced per hour at optimum flow rate. The energy expenditure required to produce ethanol at the mini- scale continuous fermentation system used in this study did not give a positive energy balance. Scale-up of continuous fermentation might increase the productivity of ethanol production and save energy input. Operational parameters (such as flow rate, working volume of fermentor etc.) need to be further examined and Optimized simultaneously. to my father and mother 11 ACKNOWLEDGEMENTS I am sincerely grateful to Dr. Jerry N. Cash for his most valuable suggestions, never-ending patience, understanding and encouragement throughout the courses of my education at Michigan State University. As my major professor, he offered for both professional and personal growth. Grateful appreciation is also expressed to the other members of my guidance committee, Drs. J.I. Gray, D. R. Heldman, G.L. Hosfield, P.C. Markakis, and C.A. Reddy for their time, interest and helpful suggestions. I wish to thank Mr. Robert L. Ellis, President of Mid- America Pntato Co., for his full cooperation in allowing this research to be conducted on the company's premises. Appreciation must also be expressed to Ore-Ida Potato Co., and Superior Potato Chip Co. for their coorporation and assistance during the data collection phase. Acknowledgement is extended to the Michigan Potato Industry Commission for their partial financial support of this work. Special thanks go to Sterling Thompson, Daphne Chadbourne, John Larkin and my fellow colleagues for their assistance, support, and friendship throughout my graduate program. Finally, I am most grateful to my parents,sisters,and iii brother for their limitless support and encouragement during my graduate program. iv TABLE OF CONTENTS LIST OF TABLES - - - - — — — - - - _ LIST OF FIGURES - - - — - - - — - - - INTRODUCTION - - - - - - — _ - - - LITERATURE REVIEW A. B. C. Ethanol: Outlook for Production Ethanol Production Processes - - — - - (1) Chemical Synthesis - - - - _ - - (2) Fermentation Process - - — — — — Continuous Fermentation - - — — — - MATERIALS AND METHODS A. B. C. Potato Process Wastes Determination Potato Process Waste Hydrolysis Procedures- Fermentation (1) Yeast Strain Selection - - - - - (2) Batch Fermentation - - — - - _ (3) Continuous Fermentation - - — _ - Analytical Methods (1) Cell Number Determination (2) Sugar Determination — - - _ _ (3) Ethanol Determination — - _ _ - (4) Starch Content Determination (5) Moisture Content Determination - - (6) Ash - - - - - _ - - l - - PAGE vii viii 15 21 24 25 26 27 28 28 29 3O 30 31 RESULTS AND DISCUSSION A. Compositional Characteristics of Solid Streams - - B. Batch Fermentation C. Continuous Fermentation D. Energy Balance for Ethanol Production SUMMARY AND CONCLUSIONS APPENDICES - - - vi Waste 32 43 46 49 64 68 LIST OF TABLES Alcohol production cost components . . . . . . . Profile of waste from different potato processing operations . . . . . . . . . . . . . . . . . . . Ethanol production in 20 percent glucose media . Calculation of the amount of potato processing waste to yield 1 gallon ethanol . . . . . . . . . . . . Calculated steam energy requirement for liquefaction and saccharification . . . . . . . . . . . . . . Calculated total energy input prior to distillation vii Page 33 .43 51 55 59 LIST OF FIGURES Figure Page 1. Possible routes to petrochemicals from potato processing waste 0 O O I O O O O O O O O O O O O I O I O O 7 2. Fermentation of glucose to ethanol and C02 by yeasts . . . 12 3. Schematic diagram of sieve tray distillation of ethanol. 14 4. Scale-up sketch of the processing area . . . . . . . . . . 22 5. French fry plant flow chart and waste generation units . . 23 6. Moisture content of waste from individual processing units 0 O O O O O O O O I O O O O O O O I O O O O O O 35 7. Starch contents of waste from individual processing units 0 O O O O O O O O O O O O O O O O I O O O O O O 36 8. High performance liquid chromatogram of sugars from ground potato processing waste . . . . . . . . . . . . 39 9. High performance liquid chromatogram of potato processing waste after completion of liquefaction . . . . . . . . 41 10. High performance liquid chromatogram of potato processing waste after completion of saccharification . . . . . . 42 11. Batch cell growth curve with ethanol production and glucose consumption versus time . . . . . . . . . . . . 45 12. Ethanol production and glucose residue at different dilution rate . . . . . . . . . . . . . . . . . . . . . 48 13. Flow chart for anhydrous ethanol production from potato processing waste . . . . . . . . . . . . . . . . . . . . 50 viii INTRODUCTION The current U.S. effort to develop synthetic fuels and fuel extenders is a result of the Organization of Petroleum Exporting Countries (OPEC) dramatic increase in prices of crude oil on the world market over the past few years. The OPEC sales price in 1973 was $3.39 per barrel, which increased to an average of 3 31.59 per barrel at the end of 1980. In the United States, the net petroleum imports were 7.9 million barrels per day in 1979. Alcohol fuels, in the form of gasohol, provide an attractive method for reducing U.S. dependence on imported crude oil. Biomass in its various forms (municipal solid waste, crop residues, and woody materials) is the largest potential renewable source of materials for producing alcohols. The potato processing industries in Michigan generate several hundred thousand pounds of potato waste each day. Some of this waste is sold as low price cattle feed but a large percentage is disposed of via waste disposal firms or through municipal waste treatment systems which charge the companies for their service. The charge is usually based on BOD (Biological oxygen demand) levels, which in potato waste are vaqr high,so the cost of disposal is also high. Therefore, any procedure which could neutralize the disposal 2 charge would be advantageous and if the resultant product had some economic value, a large liability could be converted into an asset. Since the United States has a energy crisis, and an excess of potato processing waste, there should be Opportunities for an economical conversion of potato starch to ethyl alcohol which could supply a source of energy while lowering the cost of disposal. Opportunities for waste product utilization rely on defining the sources, amounts and composition of waste streams. Therefore, this research was designed to (I) determine the amounts and compositional characteristics of solid waste streams from individual unit Operations in a small-scale potato processing industry, (2) investigate the best source of fermentable substrate from different unit operations and use the most efficient enzyme conversion technique to hydrolyze potato processing waste, (3) demonstrate the production of ethanol by batch and continuous fermentation systems from potato processing waste, and (4) analyze the net energy balance for the production of ethanol from potato processing waste. LITERATURE REVIEW A. Ethanol: Outlook for Production In 1973 and early 1974, the Organization of Petroleum Exporting Countries(OPEC) dramatically increased its prices for oil. The OPEC sales price in 1973 was $3.39 per barrel, which increased to an average of $11.28 per barrel in 1974. Further price rises occurred throughout the decade but were largest in 1979 and 1980. In September 1980, the average OPEC sales price was $31.59 per barrel, and at the end of 1980, spot checks on gasoline prices in New York showed $40.00 per barrel. At the present time, OPEC still has not fully used its monopoly power (Jenkins, 1981). The increasing prices of petroleum in world markets and consuming countries' realization that they are at the mercy of the exporting nations prompted the search for alternate fuels that could reduce their petroleum imports. In the United States, 1979 energy consumption was 80 quadrillion Btu, 18.4 quadrillion Btu of which were imported. Of these imports, 16.9 quadrillion Btu were crude oil and refined petroleum products. This is equivalent to net petroleum imports of 7.9 million barrels per day in 1979. The alcohol fuels, ethanol and methanol, provide an alternative source of energy that has the potential to reduce the importation of liquid petroleum fuels. To date, most of the emphasis has been on ethanol made from grains, 4 sugar crops and waste biomass. The government estimates that between 80 and 100 million gallons of fuel-grade ethanol are currently being produced annually in the United States. The Department of Energy(DOE) has set goals for alcohol production of 920 million gallons per year by the end of 1982 and 1.8 billion gallons per year by the end of 1985. A major advantage of alcohol as a fuel is that it can be produced from agricultural crOps and is, therefore, renewable. Alcohol production on a large scale provides a means of utilizing available surplus crOps and stabilizing crOp prices.(Christensen and Gerick, 1980) A major disadvantage of ethanol is its cost of production. A cost breakdown for alcohol production indicates that the grain feedstock accounts for the majority of the production cost. Table 1 shows a breakdown of the costs in percentages for alcohol production. In addition, the volatile nature of the grain commodities market significantly increases the risks to the economic viability of alcohol production. Once analyzed, these factors serve to cool entrepreneurial enthusiasm fo alcohol production ventures which could, in turn, worsen the fuel shortage condition in the future (Christensen and Gerick, 1980). This situation generates a good deal of interest in the potential for using a significantly less expensive material, such as agricultural wastes, as a feedstock for alcohol production. The quantities of potato processing wastes make them a potentially significant source of substrate for alcohol production. According to Talburt and Smith (1974), the potato processing industry in the United State generates about 1.3 x 1&9kg waste annually . A more TABLE 1. ALCOHOL PRODUCTION COST COMPONENTS (grain based plant) Percent Feedstock 65 Labor 3 Enzymes and Chemicals 10 Repairs and Maintenance 3 Insurance 1 Utilities 13 TOTAL 100 Excludes total captal and financing cost. (From Christensen and Gerick, 1980) recent estimate by the Michigan Potato Industry commission indicates that this figure may be as high as 3.6 x 109Kg per year. Lemmel et a1.(l978) indicates that during processing about half of the potato is lost in various forms of waste such as peel, trim, filterable particulates, and soluble fractions which are lost in the washing and blanching procedures. A investigation by Shirazi (1979) provides 6 results for a medium- scale processing plant for french fries. The results indicate that 162 tons or 324,000 lbs of raw potato waste are being generated per day. Since these wastes contain large amounts of starch, there should be opportunities for conversion to ethyl alcohol. According to Miller (1975), the theoretical yield of ethanol is 0.568 pounds per pound of starch, based on a theoretical glucose conversion of 1.094. In commercial operations, yields generally are 90 to 95% of theoretical which means the yield of ethanol is 0.51 to 0.54 pounds per pound of starch. Based on this conversion, a medium-scale processing plant for french fries can produce 38,637 lb ( appr. S870 gallons) ethanol per day. The utilization of these wastes for production of ethanol reduce waste treatment costs for the potato processing industry by a significant amount ( Christensen and Gerick, 1980) An estimated 130 million gallons of ethanol could be produced per annum by fermenting the potato wastes. Additionally, as shown in Figure 1, the glucose from potato process wastes could be used as the basic raw material for the manufacture of many chemicals- currently Obtained from petrochemical feedstocks ( DOE Newsletter, 1980). B. Ethanol Production Processes Ethanol is one of the most imrortant organic chemicals in industry. Ethanol is employed as a fuel, a solvent ,an mumm3 wcwmmmooum Oumuom Eouw mamuwausuouuom Ou mousom manammom .H muswwm 33.1.8 1222......323. Hearst non—Emboacguoboa lamina TI_>CH0E>XOLU>IJ nocafotazoacguoroa I 20.0 650361 «095 mucouomtam A _Otfl._0ml 3.350530“. 3:53.: A QWOHODLLJ , i - w 75820—4 ms. m>> , . mmmooi 9.an / oztzcoituuroa Illa—EEOERE 33323320an330< 35> / a3300< Ioutuxfii ozoo< Ail 0352303‘ «3303‘ alllllm.u< ozou< 6535 t 3cmxo£>5¢u~ albufroflatbam .Ocaaamuc _\o:o=u3:m Cognac ozofiiw n A o:o.>5m¥ 8 extractant and an antifreeze. Ethyl alcohol is produced in the United States by two major procedures, fermentation and chemical synthesis. At the beginning of the 20th century ethanol was produced on a large scale by fermentation . In recent years 70 percent of the ethanol made in the U.S. has been made by chemical synthesis, chiefly because of the cost Of sugar and starch (Eveleigh, 1981). Practically all beverage alcohol is still produced through the fermentation of cereal grains, molasses, and other materials with high starch and sugar content. Chemically, both alcohols are essentially the same and may be used interchangeably. (1) Chemical Synthesis Practically all synthetic alcohol is now produced from ethylene, which is Obtained from petroleum and natural gas. The original commercial synthetic process involved the reaction of ethylene with sulfuric acid and hydrolysis of the ethyl sulfate to ethyl alcohol. The direct catalytic hydration of ethylene with water is a later development and is increasingly used. Conversion yields of ethylene to ethanol Of up to 972 have been reported ( Miller, 1975). The chemical balance of the conversion of ethylene into ethyl alcohol showed in the following equation. Catalyst CH2=CH2 + H20 C2H50H Ethylene Ethanol (2) Fermentation Process The production of ethanol via fermentation is a well established process consisting of five basic steps: feedstock preparation, saccharification, fermentation, distillation, and dehydration. Feedstocks can be selected from among many plants that either produce simple sugars directly or produce starch and cellulose. The simple sugars from such plants as sugarcane, sugar beets, or sorghum can be obtained by crushing or pressing the material. The low sugar bagasse and pulp which remain after pressing can be leached with water to remove residual sugars. The fibrous cellulosic material theoretically could be treated chemically (acid hydrolysis) or enzymatically to yield more sugar . However, no commercially available process currently exists. The preparation of a starch-type material such as grain consists of transporting the material over a series of vibrating screens and magnets to remove any foreign material. The grain is then crushed or ground to a fine material, called meal, to increase the surface area available for further processing. Saccharification is the process by which the starch contained in the grain feedstock is converted into simple sugars which can be fermented into ethanol. The saccharification process consists of several steps including slurrying, precooking, cooking, and final 10 conversion. After the meal is slurried with water, alpha amylase is added to convert the starch contained in the grain into complex sugars called dextrins. Through proper temperature control, the starch contained in the grain cells is released in stages which allows the enzyme to act on virtually all of the starch. The stage—wise conversion prevents the excessive viscosity buildup in the slurry which would occur if all of the starch were released at once. When sufficient time has elapsed so that the majority of the starch originally contained in the grain is converted into dextrin, the mash is pumped to the saccharification tank. In this tank another enzyme, glucoamylase, is added to the mash which converts the complex sugars into simple fermentable sugars. Upon completion of this conversion step, the saccharification process is complete. The sugar solution produced in the saccharification process is converted to alcohol in the fermenters. Most of the ethanol formed in nature and produced by the fermentation industry comes from the anaerobic breakdown of glucose and other hexoses by yeast cells, notably of the Saccharomyces species. Gay-Lussac (1815) has shown that hexoses are converted into ethanol and 002 according to the following equation: Cal-11205 4- Yeast ——> 2C02 ‘I' 2 C2H50H 11 If complete conversion is attained, about 51 percent of the sugar is converted to ethanol and 49 percent to CO . Actual yields of ethanol generally fall short of predicted theoretical yields because about 5 percent of the sugar is used by the yeast to produce new cells and minor products such as glycerols, acetic acid, lactic acid, and fusel oils. Figure 2. summarizes the ethanol fermentation as carried out by yeasts (Gottschalk, 1978. It is apparent that yeasts employ the Embden-Meyerhof pathway for glucose degradation. Thus, 2 mol of pyruvate are formed from 1 mol of glucose and pyruvate is decarboxylated to acetaldehyde by pyruvate decarboxylase, which may be regarded as the key enzyme of ethanol fermentation. The acetaldehyde formed is then reduced to ethanol by alcohol dehydrogenase. In the whole pathway, there is no external H-acceptor like oxygen, so NADR2 -producing and NADHZ-consuming reactions have to be balanced out. Fermentation is strongly influenced by temperature because the yeast performs best in a specific temperature range. The rate of fermentation increases with temperatures in the range between 80 F(27 C) and 95 F(35 C), but at higher temperature the rate of fermentation gradually drops off, and ceases at temperatures above 109 F(43 C). The actual temperature effects vary with different yeast strains and typical operating conditions are generally closer to 80 F(27 C) than 95 F(35 C)(Priester,1980). Nagodawithana and 12 glucose 2 ATP 2 ADP fructose-1 ,6-diphosphate I 2 ethanOl 2 glyceraldehyde-3-p , ............................ a? >2NAD alcohol . C dehydrogenase; 2NADH2< : OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO ’ 2 1,3-diphosphoglycerate rillllIIIHVIIIIIVIIaIlfgIIIIIE €02 2 ADP 2 A T P a decarboxylaseE 2 pyruvate 2 ATP 2 acetaldehyde 2 3-phosphoglycerate 2 ADP 2 phospho-enolpyuvate 2 2-phos‘phoglycerate 2 H20 L Figure 2. Fermentation of glucose to ethanol & 002 by yeasts ( From Gottschalk, 1978) 13 Steinkraus (1976) have shown that alcohol dehydrogenase lost its activity in brewers' yeast under conditions of "rapid fermentation' at 30 C but retained its activity in cells under similar condition at 15 C. The fermentation reaction gives off energy as it proceeds (about 500 Btu per pound of ethanol produced) so the fermenter may need to be equipped with active cooling systems, such as cooling coils and external jackets, to circulate air or water for convective cooling (Priester, 1980). The beer stream leaving the fermenter contains 8 to 12 percent ethanol. Almost all of the water and essentially all impurities contained in this beer are removed from the ethanol in the distillation section. The alcohol-water solution exits from the top of the column and spent beer exits from the bottom. The distillation sieve tray column shown in Figure 3. is the most common single-vessel device for carrying out distillation. The liquid flows down the tower under the force of gravity while the vapor flows upward under the force of a slight pressure drop. The portion of the column above the feed is called the rectifying or enrichment section. The upper section serves primarily to remove the component with the lower vapor pressure (water) from the upflowing vapor, thereby enriching the ethanol concentration. The portion of the column below the feed, called the stripping section, serves primarily to remove or strip the ethanol from the down-flowing liquid. l4 Condenser Noncondensible: OOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOO To EthanOI Dehydration or Storage Stillage Storage Steam Beer Column Rectll‘ying Column Figure 3. Schematic Diagram of Sieve Tray Distillation of Ethanol ( From Priestcr, l980 ) 15 The composition of the alcohol-water leaving the stripping column can vary widely, depending upon the design of the system. This stream typically ranges from 80 to 160 proof. The alcohol-water stream leaving the stripping column enters the rectification column where distillation continues to separate the ethanol from the water. An azeotrope between water and alcohol prevents the ethanol from being concentrated past 192 proof in a simple distillation system, and in practice, 190 proof is normally achieved. The 190 proof ethanol leaves from the top of the rectification column while the water leaves from the bottom. The final step in the production of absolute ethanol is the dehydration process which removes the remaining 5 percent water in the alcohol-water mixture. The most common method currently in use to produce anhydrous ethanol is ternary azeotropic distillation. In this process, another component, such as benzene, is added to the alcohol-water azeotrope to form a ternary azeotrope. Distillation of this minimum—boiling ternary azeotrope allows the anhydrous alcohol to separate from the water-benzene mixture and exit the bottom of the column. The water-benzene stream is then treated to recover the benzene. This system allows continuous recycling Of benzene and losses of this material usually do not exceed 0.05 percent, based on the volume Of the absolute ethanol produced. C. Continuous Fermentation l6 Monod (1949) altered the batch culture process by continually supplying Fresh nutrient medium to a well- stirred culture, while simultaneously withdrawing the spent broth containing cells and products. In a continuous microbial culture, growth can be maintained for prolonged periods. Furthermore, a steady state can be maintained such that the cell concentration, specific growth rate, and culture environment ( e.g. nutrient and product concentrations) do not change with time. As a consequence, continuous culture provides a unique tool for the continued production of cell mass and products under Optimal environmental conditions. The essential components are the constant-volume culture vessel, the medium-feeding device, which allows the medium feed rate to be controlled, and the sterile medium reservoir. In addition, it is usually desirable to control pH and temperature with a suitable controller, and aeration with a constant air flow rate. Several types of continuous fermentation systems exist but by far the most common is the chemostat. The nutrient medium is fed by a pump to the culture vessel where volume is maintained constnt. The medium is designed so that all but a single essential nutrient are available in excess of the amount required to synthesize a desired cell concentration. The single growth-limiting nutritent controls the size of the steady-state cell population. Chemostat Model ( Material Balance on Cells): 17 A material balance on the cell mass written around the fermentor is given by Equation 1. Cell IN - Cell Out + Cell Growth -Cell Death = Cell Achmulation _E_ _ _F_ _ _ dX Where Xpand X are the cell mass (g/l) in the feed and the fermentor respectively, F is the medium flow rate (l/hr), V is the fermentor volume (1), u and a are the specific growth and death rate (hfi) respectively,as shown by Equation 2, and t is time (hr). '"i at (2) Liz: Usually, with a singkr-stage chemostat, the feed stream is sterile and X -0. Also in most continuous cultures, the specific growth rate is much greater than the death rate (“5N1 ) so equation 1 may be simplified as shown in Equation 3. F —_‘1.)_(_ (3) As a consequence, at steady state, when dX/dt - O, .=_5. Thus the specific growth is determined by the flow rate of the medium divided by the culture volume. This ratio is defined as the dilution rate D F _u_ '"xx‘_ and at steady state the specific growth rate is equal to the dilution rate. 18 The continuous fermentation process has come a long way since its introduction. Many reviews (Herbert, et al., 1956; Holme, 1962; Malek and Ricica, 1969; Tempest, 1970) have appeared on the theoretical and applied aspects of this technique and some research has been done concerning prodction of ethanol by using continuous fermentation technique. The low fermentation rates sometimes obtained in continuous ethanol fermentations have been shown by numerous workers to be caused by a lack of oxygen ( Cysewski and Wilke, 1974 ). Andreasen and Stier (1953) have shown that adding an unsaturated lipid, ergosterol solubilized in the surfactant Tween 80, helps to eliminate the oxygen requirement. Cysewski and Wilke (1978) studied the optimum conditions of Sgecharomyces cerevisiae ATCC No.4126 for continuous fermentation. They indicated that optimum oxygen tension, sugar concentration and cell-mass concentration are 0.07 mm Hg, 10 Z, 12 g dry wt/liter, respectively. Bazua and Wilke (1978) studied the kinetics of a continuous fermentation with Sgcgharomyces cerevisiae ATCC No.4126 and found that continuous fermentation of ethanol is a kind of noncompetitive inhibition. Their results compared with Holzberg (1967) and Aiba et al. (1968) who found that the kinetic pattern of ethanol production cannot be extrapolated from one microorganism to another. Ethanol production by fermentation in continuous culture is limited by two factors : ethanol inhibition and a 19 low cell mass concentration. Cysewski and Wilke (1977) employed a cell recycle system to overcome the low cell- density limitation in a continuous operation and get a fourfold increase in ethanol productivity. In order to eliminate ethanol inhibition, Ramalingham and Finn (1977) employed Saccharomyces cerevisig§_12£: ellipsoideus, Strain 223 in the Vacuferm process which is to remove ethanol by conducting the fermentation under reduce pressure and distilling off the alcohol as it is formed, a three-fold higher sugar concentration can be fermented in only one- third of time needed in a conventional process. This saving in energy represents about 7 Z of the latent heat required for distilling the alcohol. Cysewski and Wilke (1978) combined vacuum and cell recycle Operations to obtain a final cell (Saccharomyces cerevisiae ATCC No.4126) density of 124 g dry wt/liter which produced an ethanol productivity of 82 g/liter hour or almost 12 times that obtained with simple continuous operations. Other techniques such as extractive fermentation, membrane extractive fermentation, and selective membrane fermentation are employed to eliminate ethanol inhibition. In extractive fermentation processes, ethanol is continuously removed from the fermentor beer by solvent extraction. A side stream of beer is tapped from the fermentor, the cells are removed and recycled, and the clear beer is contacted with a liquid extractant. The extractant 20 must be non-toxic to yeast, have a high affinity for ethanol, be selective for ethanol over water and should not form an emulsion with the fermentor broth. Dibutylphthalate and super critical carbon dioxide have been proposed as potential extractants, but have not been evaluated beyond laboratory scale ( Wilke and Mairorella, 1981). Membrane extractive fermentation is similar to extractive fermentation except that the extractant is separated from the fermentor broth by a permeable membrane. The extractant polyprOpylene glycol p-1200 has been identified as suitable for membrane extraction, having a distribution coefficient of 0.6 and being only slightly toxic to yeast (Wilke and Mairorella, 1981). Selective membrane fermentation is like that for membrane extractive fermentation, exc pt that no extractant is used. The membrane itself performs the separation, facilitating ethanol diffusion through the membrane while retarding water and other beer components. Selective ultrafiltration membrane capable of maintaining the fermentor ethanol concentration at less than 60 g/l while yielding a product concentration of 120 g/l have already been developed and membranes capable of maintaining beer concentration at below 20 g/l should be available soon ( Wilke and Mairorella, I981). MATERIALS AND METHODS (A) Potato Process Wastes Determination Data and sample collection were conducted at a small scale potato processing plant. The potato processors used either Russet Burbank or Kennebec potatoes, and their primary products were french fries of various sizes and cuts. The general scaled—up sketch of a french fry processing plant is displayed in Figure 4. For the small scale potato processing plant, the major units of solid waste are generated from 8 different units. These are, grading,cull potatoes,silt screened waste, peel loss, scrubber loss, trimming loss, sizer loss , dry handled waste, and miscellaneous which includes hydrosieve and centrifuge waste (see figure 5). The hydrosieve collects all large solid waste carried in liquid effluent streams, and the centrifuge collects all small particles in liquid effluent streams. Besides these 8 waste generating units, the final hopper which combines scrubber loss, trimming loss, sizer loss, and miscellaneous, was examined. Data collection occurred on four dates over a four-week period in mid—Autumn, 1980 at the small-scale plant. Processing operations with measurable amounts of solid waste were evaluated. At each processing operation the mass of potato waste was manually collected and measured for a given 21 22 AhcmmEoo huh nucsum moauofi ~¢.~ .eaos-n u:_u..-s.o no. Go... no—u _..I..._.‘: a—‘ -.-.a o——0n\‘_lv—u ——- sos.-..- .u<.:.—c_.x unusua. .nu Haul u. .. All. L.—.-.nr-o~ muu< mammmuuoum may mo :uuoxm maloamum .q unawam |.. .u nu , . WM”; 0:: .....E is ._ sea... A“ .I. . O l Av _ n> Ilv mEEEtF is A: Cmmuow umgmgmo AIIfiCD 0:0.“me AIIOwNuOQ 3mm 24 period of time. The average of two trials was used. On each data collection date, flow measurements (average of two trials) and samples (for composition analysis) were collected at each Operation. Samples were analyzed for total solids, moisture content, and starch content. Compositional data were expressed on the basis of percentage (w/w) of total incoming raw material solids and percentage of total waste. (B) Potato Process Waste Hydrolysis Procedures The composition Of wastes from 8 individual operation units was examined. The starch content and moisture content were used to determine the best substrate source for enzyme hydrolysis and yeast fermentation. The system is designed to atmospheric batch liquefaction and saccharification potato process waste as follow: (1) Finely Ground PPW. PPW was ground by a comminuting machine ( The W. J. Filzpatrick Company, Chicago, USA) using a U.S. number 8 screen (12 to 16 mesh). (2) The ground mash was then adjusted to a pH of 6.0 to 6.5 with a 10 Z lime slurry. (3) Liquefaction: A 0.35 percent TAKA-THERM alpha amylose enzyme (percentage of dry starch content in total batch) was added, with continuous agitation, the temperature was raised to 90 25 C ’194 F)and held 90 minutes until liquefaction was complete. Complete liquefaction was judged by determining the reducing sugar content of the mash by using HPLC to determine the sugar content. An alternative test was use of an iodine solution to test the filtered mash. A light yellow to light red color indicated complete liquefaction. (4) Saccharification: The batch was cooled to 57 to 60 C (135-140 F) and the mash was adjusted to pH 4.210.2 with dilute hydrochloric acid. A 0.3 percent DIAZYME L-100 glucoamylose enzyme (percent of total dry starch) was added with continuous vigorous agitation of the batch. The glucose concentration of the mash was evaluated by using HPLC to determine when complete saccharification was attained TAKA-THERM and DIAZYME L-100 are registered trademarks of enzymes produced by Miles Laboratories, Inc., P.O. Box 932, Elkhart, IN. 46515. (C) Fermentation (1) Yeast Strain Selection: The first item in the fermentation was determination of yeast strains suitable for ethanol production. Two commercial yeasts, Diamond V Mills Saccharomyces cerevisigg and Red Star distiller's active dry yeast (DADY) Saccharomyces cerevisigg_were evaluated for their potential to produce ethanol. A 20% glucose in YPD (yeast extract, 26 peptone, dextrose) media (The medium is made by 3 g malt extract, 3 g yeast extract, 5 g peptone, 200 g in 1 liter water, and pH adjusted to 5.0 to 5.5.) was innoculated with each strain of yeast at the rate of 1 ml of yeast containing culture media (106- 107 cell/m1) per 50 m1 of fresh media. The innoculated media were placed in 125 ml flasks and incubated at 30 C with constant agitation for 48 hours. Ethanol concentration in the media was determined by gas chromatography. Glucose content of media was evaluated by HPLC. (2) Batch Fermentation The batch experiments were performed in 1 liter and 6 liter fermentor vessels, respectively. The 1 liter fermentor vessel employed a Bio-Flo Model C30 minifermentor with electronic temperature control a working volume of 550 ml was used in this portion of the experiment.. The fermentor was sterilized and inoculated with 1.5 g Red Star DADY ( manufactured by Universal Foods Corp., Milwaukee, WI). After inoculation, aeration was employed for 30 minutes through the built-in mechanical air pump. The temperature was maintained constantly at 30 C. Magnetic stirrers were used for mixing, and a sampling was made through a sampling valve every two hours during the 24 hour interval. The sample was immediately examined for viable cell numbers, hexose residue and ethanol concentration. Ethanol 27 concentration was determined by gas chromatography. Glucose content was evaluated by HPLC. Viable cell number was determined by a standard plate count method. The six liter fermentor used a working volume of 5 liter. The fermentor was inoculated with 13.6 g Red Star DADY and aerated for 30 minutes. A constant 30 C temperature was maintained and mechanical stirring was used for mixing. After 24 hours the hexose residue and ethanol concenrtration were examined. (3) Continuous Fermentation These experiments were carried out in BIOFLO-C3O Bench Top chemostat minifermentor (New Brunswick Scientific Co., Inc.) having a working volume Of 420 ml. Sterile hydrolyzed potato processed waste medium was transferred to the culture vessel by means of a variable speed peristaltic metering pump. TO every 1000 ml of sterile medium 4 ml of ergosterol stock solution was added as indicated by Andreasen and Stier (1953). The medium reservoir, the fermentor, and the piping were sterilized in an autoclave at 120 C for 15 minutes. The process was allowed to proceed batchwise for approximately 10 hours at which time, the ethanol concentration was approximately 6 Z (V/V) and cells were in their stationary phase. When these criteria were met, the fermentor was connected to a feed reservoir to start continuous fermentation. Sterile potato process waste 28 medium was supplied constantly at the designated flow rate of 25 ml/hr. Sampling was made after 3 retension time periods, and continuing sampling 1 to 2 retension periods by every 4 hours to confirm whether or not steady state had been achieved. If the glucose residue and ethanol concentration did not change after two or three samplings, steady state was assumed. At the steady state, the sample was taken through a series of dilutions and platings to determine the viable cell number. The above procedure was carried out after decreasing the flow rate to 15 ml/hour and then increasing it to 50 ml/hour. (D) Analytical Methods: The analytical methods for obtaining viable cell number, glucose and ethanol concentration, starch content, moisture content and ash were as follows: (1) The viable cell number was determined by the standard plate count method of Marth (1978). One ml of sample was serially diluted in 99 ml of sterile distilled water, before pouring onto plates of acidified potato dextrose agar (APDA). P‘ates were incubated at room temperature and yeast colonies counted after 72 hours. (2) Glucose, fructose, and maltose were determined by HPLC methods. The sample was centrifuged at 3000 RPM for 5 minutes. A 2 ml aliquot of supernatant juice was then mixed with a 2 m1 aliquot of methanol and centrifuged at 3000 RPM 29 for 10 minutes. The supernatant juice was run through a sample preparation filter, which removes particles 0.5 um or greater. The filtrate was passed through a C18 Sep Pak (Water Associates) before injecting 10u1 to 20 ul of sample into the HPLC. Standand glucose, fructose and maltose solutions were injected before or after each run to obtain a calibration curve that correlated peak heights versus concentrations. A Water Associates liquid chromatograph equipped with a M45 pump, a U6K injector, and a differential refractometer was used. The detector signal was recorded on a Beckman Instruments 10" recorder. The column used was a 3.9 mm i.d. x 30 cm column packed with uBondapak/carbohydrate packing. The mobile phase was acetonitrile - water (75:25). Operating conditions were: flow rate of 1.7 ml/min.; dectector sensitivity Of 8 X, and chart speed Of 0.5 inch/ min. (3) Ethanol concentration was measured with a Hewlett Packard Model 5840 A gas chromatograph equipped with microprocessor control and integrator. Operating condition 8 were as follows: Column --2 mm i.d., 0.64 cm 0.D. and 1.83 m long glass column packed with Porapak 0, 100/120 mesh were used. Injector temperature --160 C Flame ionization detector temperature -- 180 C. Carrier gas-- Nitrogen at a flow rate of 40 ml/min. 30 Combustion gases -- hydrogen and air Sample injection-- One ul Standard ethanol solutions were injected before and after each run to Obtain a calibration curve that correlated areas versus concentrations. (4) Starch Content Determination The starch content was determined by polarimetric method developed by Dim1Tr (1964). A sample about 8 g of ground potato was weighed into a test tube. Sample preparation proceeded as outlined by Dimler, with the stannic chloride pentahydrate solution used in place Of uranyl acetate solution. The optical rotation of the prepared sample solution was determined using a Perkin-Elmer Model 141 polarimeter. The starch content of the sample was calculated using the equation: I starch, dry basis - a x 106 1 x [ajD x w x (100 - ZHZO) where: a = Observed angular rotation l a length of the Optical cell, dm (0)0 - specific rotation of starch ( for potatoes, 203.0) w - sample weight, g 2 H20 - moisture content, determined in section (5) (5) Moisture Content (Total Solids) Determination Moisture content was determined using the method described in AOAC (14.002) (1975). Two samples of product were obtained at each sampling point and duplicate assay 31 were run on each sample. (6) Ash The dried sample from the moisture determination were place in a muffle at 525 C (AOAC 1975) and left until a white ash was obtained, approximately 24 hours. The ash content was calculated as: Z ash, dry basis = Mass of ash X 100 Z Mass of solids prior to ashing RESULTS AND DISCUSSION Table 2. shows the percentage of waste in different operation lines, the total waste percentage of each and percent starch content of total wastes. An average of 36.66 percent (w/w) of the total incoming raw material was lost in the various processing Operations with the greatest amount of waste (34 percent of total) coming from the peeling loss. Sizer loss was 20.3 percent,trimming loss was 16 percent, and miscellaneous, which includes hydrosieve and centrifuge losses, 16 percent. The final hopper (which includes scrubber,trimming,sizer and miscellaneous) contained 59.3 percent of the total waste and 76 percent of all available starch. The peeling, sizer, and trimming contained 70.3 percent of total waste. These results are similar to those reported by Leite and Uebersax (1979) who have identified peeling, trimming and cutting as the processing operations resulting in the most significant losses. The 36.66 percent mass loss of the raw potato differs from a recent NSF report (Heldman 1979) , indicating a mass loss of 60 percent Of the raw potatoes. Data show mass losses with a range of 28 to 56 percent occurring over the sampling period at the small plant. The highest trial of 56 percent mass losses is very close to the Shirazi(1979) and Heldman(1979) investigation. The 36.66 percent loss seems to imply an improvement in Operation and efficiency since the Heldman IQ .Luumum HmuOu «O N 00 can mumms 00000 «O N m.mm mocamucoo £0053 macauumum mmonu nmmsauca pounce annaw 0:90 3 IIIIIIIIIIIIIIII IIII IIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIII IIIIIIIIII II IIIIIIIIIIIIIIIIIIIIIIIIIIII 3 00.0 0.000 00.00 00000 A owsmwuucoo 00.0 0.00 00.0 0 0>00000000 000000000000: 00.0 0.00 00.0 0000 00000 000000 00.0 0.00 00.0 0000 00005000 000000 00.0 0.0 00.0 0000 00000000 00.0 0.0 00.0 0000: 00000: 000 00.0 0.00 00.00 0000 0000 00.0 ~.o 00.0 00003 vocmmuum 00.0 0.0 00.0 0000 .0000 .0000000 000m: Hmuoe 00 00003 00009 Oumuom 30x wcwsoucu mafia: c00um0000 ucmucou nuumum ucmupmm mo acouumm Hmuoe mo assumed mcoHumummo wcammmqum Oumuom ucmummmfla 5000 00003 00 000moum .N 00200 34 (1979) investigation. Figure 6 shows the moisture content of waste from individual processing units. The highest moisture content is in scrubber loss which contains about 89 percent water. The other individual processing unit waste streams had moisture contents ranging from 78.68 percent to 86.56 percent. The variation between 4 week sample trials was very small, all less than 6 percent. These results coincide with those of Schwimmer and Burr (1967), who reported on the proximate analysis of potatoes and found the average water content to be 77.5 percent. The higher moisture content in each Operation unit is due to processing water or steam . Figure 7 shows the starch content of waste from individual processing units. The peel loss had a relatively low starch content, averaging only 18.76 percent (dry basis), with ranges between 8.25 percent to 33.67 percent during the 4 week sampling period. The peel also had a relatively high average ash content-- 16 percent (dry basis)-- a very minor amount of reducing sugars, with the remainder of the peel solids being complex carbohydrates. The trimming loss had the highest average starch content-- 61.07 percent--ranging from 87.59 percent to 45.33 percent. The scrubber loss had the largest variation -- from 58.71 to 11.11, but this is probably due to the large variation in moisture content associated with this operation. Through the entire period of analysis the final hopper had a starch 35 000cm wcwmmououm Hmsuw>0vcu Eoum 00003 no ucmucou ousumwoz .0 ouawwm cameo: 0.00 0.0.. one... .00.. 0:35 0030.. 3,200.30: asp-.0 :50. can.» 2:882... Conantom .Ooe mocootom :30 O O 0 0 0 w 0 0 0‘0 0’0 «0.00 00.00 00:00 0...: 00.00 00.00 00.00 00.3. 00.00. 3 3 an 3 on 3 2 on :— ..>< minnow x 36 000:: wcammououm HmsvflravcH Eouu 00003 no 00800000 nuuwum . h muswam 0c 3,300.0»... 4 00.. 000.. 000.. 0.003 0.0.0.. . .0. 000...." 00.88:... 0000000.... .00.. 00:00.00 :00 00.0000 on.- ...: a i =4“; AOJQ 00.004 .0. t . ”Wazw . 9.3% .. h...” 0 0 .: 00.00% 3.00 0.3m b 00 w r :60 .000 H 0R0. .00 .us. Codub .‘h..fi 00.00 00.00 00.00 0.0..0 00.00 00.0. 00.: “5.5“ Nh.O¢ Op 2 CV 00¢ ("HQ ‘19 ) "01033 x .0>< 37 content of 56.26 percent (dry basis) and the smallest range of variation in starch content. From determining the quantity and composition of waste streams (Table 2 and Figure 6 & 7), it was found that the final hopper contained 59.3 percent of the total waste, representing 76 percent of total starch,had a small range of variation of starch content (i.e. about 7 percent) and the moisture content was very consistent. Even though the peel loss contained the greatest share of waste (34 percent), it's starch content was very low (only about 13.7 percent of available starch), and it also contained a high concentration of lye (NaOH) which made it unfit for yeast fermentation without secondary treatment to neutralize the alkaline material. From these reasons, the final hopper contained the most appropriate feed stock for ethanol fermentation. The potato processing waste system was designed to include atmospheric batch liquefaction and saccharification steps based on modifications of corn batch hydrolysis procedures (Weber and Waller, 1980) and commercial technical information (Miles Laboratories and Novo Industrials). As the final hopper sample went through the feedstock preparation step, all sample particles were below 12-16 mesh in size. The sugar composition of ground potato samples were determined by HPLC. The ground potato processing waste was centrifuged, the supernatant mixed with methanol, and 38 then filtered. Twenty microliter samples were injected. Figure 8 shows the HPLC chromatogram sugars from ground potato processing waste. The chromatogram shows that the sample contains monosaccharides, disaccharides , and some oligosaccharides. Some of these sugars come from the potato itself while other sugars may be due to bacteria or microorganisms hydrolyzing the starch or oligosaccharides. Each batch liquefaction was performed with about 2900 g of ground potato waste in a 7 liter volume tank. TAKA- THERM, a liquid bactria alpha-amylase of Bacillus licheniformis var. origin, was the major enzyme used in the liquefaction step. The enzyme demonstrates exceptional thermostability, unlike malt amylase, and it can liquefy mashes at temperatures above 90 C(l94 F). The enzyme breaks down gelatinized starch to dextrins and small amounts of lower molecular weight carbohydrates. Both amylose and amylopectin are broken down in a random manner, resulting in a rapid reduction of solution viscosity. Since enzyme catalyzed reaction rates depend upon pH, temperature, ionic strength and other conditions of the envirnoment,. general technical information was supplied by Miles Laboratories and optimized by trying several trial runs. The reasons liquefaction at high temperature was chosen were (1) the catalytic conversion of starch into dextrins would proceed at a higher rate, and (2) to eliminate or inhibit microorganism in the feedstock which could utilize and 39 muwwsm mo Emuwoumeouso canvaa mocmsuomuom swam um ouswam :39”! j 0000a”) 00003 wawmmmuoum Oumuom vasouu Eoum fl“ 00.052 q a a o. 0 _ 0 . 0 u 0 — 0 000310“ .00.02.3.7332230 32:. 0:000 0.0:;000000xxonveom: 080.00 .5828 5.0 0.0m 30.0. .a on 0.08.5 Z 40 hence reduce the substrate available for yeast fermentation. The completion of liquefaction was identified by the iodine test. Figure 9 shows a chromatogram from a 10 microliter sample injection. The quantity of monosaccharides, disaccharides, trisaccharides and high molecular saccharides were all higher than in Figure 8. When liquefaction was complete, the batch mixture was cooled to 57 C -- 60 C and adjusted to pH 4.2 10.2, which are the optimum conditons for Diazyme L-IOO to convert complex sugar into simple fermentable sugars. Diazyme L-lOO is a liquid glucoamylase derived from a selected strain of Aspergillus niger var. Diazyme L-lOO is capable of hydrolyzing both a-D-l,6-g1ucosidic branchpoints and the predominating a-D-1,4-g1ucosidic linkages of starch. The enzyme is capable of achieving a complete breakdown of starch into simple fermentable sugar. Upon completion of converting dextrin into simple fermentable sugar, the saccharification process is complete. Figure 10 shows the HPLC chromatogram after completing saccharification. Samples were diluted 8 times and 10 ul injected. Monosaccharides were the only sugar present in the sample. This implies that all oligosaccharides were hydrolyzed by TAKA-THERM and DIAZYME L-lOO to monosaccharides. Most of the ethanol produced by the fermentation industry uses Saccharomyces species as the fermenting organism. The different strains of one specie have variable 41 0001601000003 0000000003.. mo 0030.30.00 00000 00003 wcw000uoum 000000 mo E0uw000sou£0 000000 0000Euomu0m nwax .m 000wam .000020302-...22330 0.2... 0:00: 0.000000000oxx0000002 .5828 h... .20— 080.00 0.0m 30.0. 0.0800 ..°3"l9-‘: . :32: . 2 2 0 - 0 - 0 _ 0 . osousw-—-=: asolnozliw ‘C 42 000H050000H0 £003 00000owmwu0noo0m mo 00000H0500 u00m0 00003 w00000uoum 00000» mo E0uwo00souno 000000 00:0Euomu0m swam .oa 0usmwm 00.055. 0 ~ . . . - o - 0 — 0 — 0 - 33°{Ul Amuumhto.0ilo._...co.000 000:0. 0.30... 0.0...0xzoneuuxxanpcom: 080.00 .5828 5... 0.0m 000.0. .x0 0.5.3.200 0.0800 43 fermenting capabilities due to their distinct levels of alcohol tolerance (Gary, 1941; Ingram, 1955; Ranganathan and Bhat, 1958) and glucose tolerance (Gray, 1945). In this study, the selection of a yeast organism for use in the fermentation of potato process waste depended on the availability of the yeast organism and its activity. Table 3 shows the results obtained with two commercial yeasts employed in the study, Saccharomyces cerevisiae from Diamond V Mills and Red Star DADY from Universal Foods. Equal amount of ethanol were produced by both organisms when innoculated into 20% glucose medium. Weber and Waller (1980) reported that the diamond V Mills yeast strain (Saccharomyces cerevisiae) is not significantly different from the high ethanol tolerance yeasts acquired from the American Type Culture Collection or the Research Center at Table 3. Ethanol Production in 20 percent Glucose Media Initial Final Ethanol Strain Glucose Glucose Concentration Concentration 2 Concentration 2 (v/v percent) Diamond V. 20 0.1 10.3 Red Star DADY 20 0.1 10.5 44 Peoria in terms of performance under conditions encountered with a grain processing system. Samples of yeast can be obtained from Diamond V Mills in bulk and from Red Star DADY in bulk or small 7 gram packages. Because of the ease of use the smaller package from Red Star DADY was selected for potato waste fermentation. Figure 11 shows cell growth , ethanol production, and glucose consumption versus time for the batch experiments in a 1 liter fermentor vessel ( working volume 550 ml). The initial hydrolyzed potato processing waste contained 12.96 Z fermentable sugar ,as glucose. After 24 hours, the fermentable sugar was almost completely comsumed and 7.8 percent (V/V) ethanol produced. The Red Star DADY yielded 93 percent efficiency of glucose utilization (conversion of glucose to its theoretical ethanol content) based on only the yeast using the glucose in the fermentor and producing 7.8 percent(V/V) ethanol. Figure 11 also shows batch fermentation kinetics of the Red Star DADY. The specific growth rate during the exponential growth phase was calculated using the curve based on viable cell counts. Under the conditions used in the experiment the specific growth rate was 0.06/hour. A productivity of about 2.05 gram Ethanol/liter-hour was calculated by dividing the weight of ethanol in one liter of supernate by the corresponding fermentation time. The specific growth rate could be increased by increasing aeration time, but 4S (gm/6w) uondumsuoa esoonls or ON on O? on on on on on Dev Orr our Oflr V (A/A %) :uawoo IOUBlHEJ or I mafia msmuo> cowuaeawcoo umooaao was coauuavoum Hocmn0m £0H3 u>0=o nuaouu Haoo £00mm .HH ouswww Amazon. 08.... A a «a on 3 S 3 a. I I d «Inn 10 .oz :00 03.0; 0 0:00:00 .ocmcum x co.0a8:mcoo 0.00030 k or a 4:9 v' cu c: or (10”) 'ON “93 alqu 46 productivity was decreased. This is due to a shift in yeast metabolism to aerobic rather than anaerobic at high oxygen tension. Less ethanol was produced with a corresponding increase in cell mass or cell number. It has been suggested that high alcohol content and fast fermentation rate are not compatible (Chen,l981). An increase in initial yeast concentration was essential to higher ethanol productivity (Chen,l981) The scale-up batch fermentation was performed in a 6 liter fermentor(working volume 4900 ml). The initial fermentable sugar concentration was 162. The yeast concentration and aeration time were similar to those used with the 1 liter fermentor. After 24 hours, the fermentable sugar was almost completely consumed and 9 Z (V/V) ethanol was produced with 90 Z efficiency of glucose utilization. The higher ethanol yield was due to the higher initial glucose concentraton in the hydrolyzed potato mash. Continuous fermentations of 13 2 glucose in hydrOlyzed potato processing waste were started in a batch mode to allow cell concentration to increase and reach the highest ethanol production yield and to avoid ”washout" of the cells. The process was allowed to proceed batchwise for approximately 10 hours at which time the ethanol content was 6 percent, V/V, and the viable cell number 6.8 x 107 cells/ml. The fermentor was connected to a feed reservoir tank to start continuous fermentation. Initially, it was 47 difficult to maintain the viable cell number at the desired level and the residual glucose concentration gradually increased, even at low dilution rates. The decline in performance was thought to be due to a nutritional deficiency (Ramalingham, 1977). Since the hydrolyzed potato processing waste medium was sterilized in the autoclave, oxygen in the medium may have been removed, thereby causing an oxygen deficiency in medium. Andreasen and Stier (1954) suggested that the oxygen requirement can be subsquently omitted by the addition of a sterol and fatty acid supplement. The continuous fermentation operated steadily after 0.4 percent ergosterol stock solution was added to sterilized medium. This resulted in a dramatic rise in yeast concentration and a corresponding drop in residual sugar. The dilution rate (D) is defined as F/V, where F is medium flow rate( liter/hr.) and V is culture volume in liters, i.e., D-F/V. Specific growth rate (u) also equals F/V at steady state of single-stage chemostate. Therefore, D-F/V-u. A theoretical Optimum flow rate of 25 ml/hour was based on the specific growth rate of Red Star DADY (0.06/hour) times the working volume (420 ml) of the fermentor. Two. additional flow rates (15 ml/hour and SO ml/hour), based on double the theoretical optimum flow rate and almost half the theoretical Optimum flow rate were also em 1oyed. Results are shown in Figure 12. While ethanol 48 (Ila/6w) anpgsau asooms) or ON on 0' on 00 Oh cm 00 Dow Orr our our untamed omousao can cofiuusvoum Hocmnum .NH ouswam amuse coausafia unuuoumwa 0a F2. 32.. cozazo «v.0 no.0 mnoé. q d 03.0.00: omooiu Ff“. J1 14. . 80.003095 .ocmfim or UOHGHPO-ld IOUBQIH (“/A)% 49 production was not significantly different at dilution rates of 0.035/hr and 0.06/hr, it was significantly decreased at a dilution rate at 0.12/hr. The low ethanol production obtained and high residue sugar content at the dilution rate of 0.12/hr may be due to the rapid dilution rate resulting in cell washout and decreased production. An advantage which the continuous fermentation has over the batch fermentation is that there is no turnaround time. If ethanol productivity with a minifermentor is compared with batch or continuous fermentation; it must be assumed that the turnaround time for the batch fermentation is 10 hours. Since this situation ethanol productivity would be 1.6 times less than by the continuous fermentation method. Energy Balance for Ethanol Production One of the most controversial aspects of ethanol production is the energy expenditure required to convert the raw material to ethanol. The production of ethanol from potato processing waste (PPW) requires energy for: grinding (feedstock preparation), enzymatic liquefaction, enzymatic saccharification and fermentation. Energy is also expended during the distillation of the ethanol. Figure 13 shows the production flow chart for anhydrous ethanol production from PPW. Table 4 illustrates the amount of potato processing waste which theoretically yields 1 gallon of ethanol based 50 PPW Feedstock l Feedstock Preparation (Grindln9,Adlust pH) 1 Liquefaction (Add TAKA-THERM Enzyme) (Cooking to 90'C. 90 mlns.) l Saccharification (Cool to 57'c-so’c Adjust pH to 4.2) (Add Dlazyme L-100) 1 Cool Medium to 30'C / \ Batch Fermentation Continuous Fermentation \ / Distillation (Stripping Column,Rectltlcatlon Column) 1 Dehydration (Ternary Azeotroplc Distlllatlon) l 200 Proof Ethanol Figure 13. Flow Chart for Anhydrous Ethanol Production from Potato Processing Waste 51 on batch fermentation data. As illustrated, 141.76 lbs of potato processing waste could produce 1 gallon of ethanol. Table 4. Calculation of the amount of PPW to yield 1 gal. ethanol l.The unit volume of beer in fermentor x 1 wet matter- wet matter/unit volume. Ex. 550 ml beer x 80% wet matter-440 ml wet matter/unit volume. 2.Wet matter x percent of ethanol content in wet matter- ml ethanol/unit volume of fermentor. Ex. 440 m1 wet matter x 7.8% ethanol content- 34.32 ml of ethanol/unit volume of fermentor. 3.0ne gallon ethanol - 3785.4 m1 ethanol 4.Unit volume of fermentor x ratio of total volume ethanol to unit volume of ethanol - total volume beer/gal ethanol Ex. 550 ml beer x 3785.4 m1 8 60663.46 ml/gal ethanol 34.32 ml 5.Tota1 volume beer x beer specific gravity- total weight of beer(gram). Ex. 60663.46 ml x 1.06 - 64303.26(grams)-141.76 lbs/gal ethanol The energy utilized in ethanol production is in the form of steam and electricity. In terms of actual energy expenditure for ethanol production, assumed the efficiency conversion to steam is 70 percent if either propane or coal are used to produce energy. The fermentation vessel employed for this example was a 35 cm-diameter, 100 cm- length vertical cylinder with a cover made of half 52 centimeter thick pyrex glass. The fermentor weighed 33 pounds and the volume was 25 gallon. Each processing step's energy requirements are illustrated as follows: (1) Grinding: An electric motor comminuting machine was used to grind PPW. The 220 volt motor drew, 19.6 amps for 30 minutes to mill 141.76 lbs PPW to 12 to 16 mesh. The formula used to calculate the BTU content of electrical usuage is as follows: (Volts x Amp x hours) x 3.414 - BTU's (1) The total energy input for grinding was 7360.58 BTU.(Appendix II) (2) Enzyme Liquefaction: In the enzyme liquefaction step, steam was used to heat the PPW substrate from 20 C (68 F) to 90 C (194 F) and keep it at 90 C for 90 minutes. The total energy input to raise substrate temperature from 68 F(Tref) to 194 F(fi;) which is sensible heat was calculated from the relationship: 0w - Mw pr (TL - Tref) (2) 0f - Mf Cpf (TL - Tref) (3) The specific heat (Cpf) for the pyrex glass container was taken from Holman (1976). The specific heat (pr) for PPW was determined from a relationship presented by Charm (1971): pr - 0.5 X}: + 0.3 Kg +1.0 Km (4) where the value of 0.5, 0.3 and 1.0 are specific heats of 53 fat, solids and water present in the product, respectively. The total sensible heat (QT) equal to the sum of sensible heat for the substrate (Qw) plus sensible heat for the container (Qf) was calculated as follows: QT - Qw + QE (5) The thermal energy input to keep the fermentor at 194 F for 90 minutes was equal to the thermal energy losses from the surface of the fermentor vessel due to convection and radiation . The convective heat transfer from the vessel surface which included the vertical cylinder and the top horizonal plates can be estimated by: CC - hc A (Tsh - Tm) (6) where hc is a convective heat transfer coefficient to be determined from the following correlations: hc - NuI K (7) L NuL- C (GrLPrL) (8) GrL = g B (Tsh - T0,) L3 (9) v2 The temperatures in equation (9) are for air near the exterior surface of the vessel and at the mean value for the vessel surface (Tsh) and the surrounding air (T0° ). The characteristic dimension L for use with the vertical cylinder is the height, and is 0.9 d (diameter) for the circular horizonal plate (Holman 1976). The constant C and m used in equation (8) were taken from Holman (1976) and 54 are for an isothermal vertical cylinder and the upper surface Of a heated plate. The constant K in equation (7) represents the thermal conductivity Of air at atmospheric pressure. The thermal energy losses from the fermentor vessel surface due to radiation were estimated from: Or - hr A (Tsh- Ta) (10) with hr = 0.0069 6 (9/100)3 (11) These espressions apply when the fermentor vessel is small in comparison to the room in which the hydrolysis and fermentation Operations are carried out (Earle, 1966). The emissivity value (2.) for pyrex glass in equation (11) was taken from Holman (1976). The total thermal energy input for enzyme liquefaction is shown in Table 5 with results expressed as total sensible heat (QT): convective heat losses (Qc) and radiative heat losses (0r). All calculations are shown in Appendix II. (3) Saccharification: After complete liquefaction, the slurry batch was cooled to 60 C (140 F) and kept at this temperature for 90 minutes to allow glucoamylase hydrolysis. The heat removed prior to saccharification equals the total sensible heat at liquefaction minus the total sensible heat at saccharification or 6958 BTU. The thermal energy input to keep the fermentor at 60 C (140 F) for 90 minutes was equal to the thermal energy 55 Table 5. Calculated Steam Energy Requirement for liquefaction and Saccharification 1002 Efficiency Energy 70% Efficiency Energy Expenditure BTU/gal Expenditure BTU/gal Liquefaction Sensible heat 16234.29 23191.84 Conductive heat losses 1919.29 2741.84 Radiative heat losses 3256.00 4651.00 Saccharification Conductive heat losses 896.47 1280.67 Radiative heat losses 1611.10 2301.57 Total 23917.15 34166.92 56 losses from the surface Of the fermentor vessel due to convection and radiation. Equations (6) to (9) were used tO calculate the convective heat losses and equations (10) and (11) were used to calculate the radiative heat losses. Values for the constants, Kinematic viscosity (v), thermal conductivity (K) and Prandle number (Pr) of equation (7) to (9) were taken from Holman (1976) for air at atmospheric pressure and a temperature of 330 Kelvin (60 C). A fermentor vessel surface temperature (Tsh) of 60 C (140 F) was employed. The total energy input for saccharification is shown in Table 5 with results expressed as convective heat losses and radiative heat losses. All calculations are shown in Appendix II. (4) Batch Fermentation After saccharification, the fermentor was cooled from 60 C to 30 C. The total thermal energy removed in this process was about 6957 BTU. The batch fermentation was conducted at 30 C for 24 hours. The fermentor was equipped with a solid-state thermistor temperature regulator and a magnetically-controlled multi-blade impeller both Of which drew electricity. The total electrical energy usuage expressed as BTUs was calculated using equation (1). The fermentor was assumed to have a 220 volt motor which drew 1 amp for the 24 hour period. The total electrical energy input was therefore 18015.88 BTU (Appendix II). 57 (5) Continuous fermentation The energy consumed in continuous fermentation was measured during experiments with a chemostat minifermentator. The minifermentator has a working volume Of 420 ml. The minifermentor was equipped with a solid- state thermistor temperature regulator, a magnetically- controlled multi-blade impeller, and a variable speed peristaltic metering pump, all of which drew electricity. Assuming the system reached steady state, the Optimum flow rate was 25 ml/hour and the ethanol concentration in the product was 6.3 percent V/V. The fermentor had a 110 volt motor which drew an average of 0.09 amp per hour. The electrical energy usuage expressed as BTUs was calculated using equation (1). The electrical energy input per hour was 33.8 BTU. Based on the given flow rate and ethanol concentration, 1.28 ml of pure anhydrous ethanol would be produced per hour. (6) Distillation Distillation was not conducted in this experiment. Geiger et al (1980) designed and built a distillation column which was Operated in the Beef and Cattle Research Center, MSU. The ten tray (10 ft.) column could generate 8000 gallon ethanol per year. Based on their results, 32,076 BTU/gal are expended in obtaining a 65 volume I ethanol from a 9 volume 2 fermentation beer (Appendix I). TO Obtain 95 volume 2 anhydrous ethanol, the total 56,578.4 BTU/gal are 58 required. (7) Ethanol Combustion Heat 1 gallon ethanol = 231 inch ethanol = 3785.39 cm ethanola 2987.81 gram ethanol. 2987.81 gram ethanol/46 gram/mole = 64.95 mole 327.6 kcal/mole x 64.95 mole - 21278.42 Kcal a 89028928.23 joule =84,378.6 BTU/gal ethanol. (8) EnergyWBalance (3) Batch Fermentation PPW processing and fermentation required 49,294 BTU to make one gallon of anhydrous ethanol (Table 6). This is not the primary energy actually consumed by processing. In terms Of primary energy expenditure ( BTU's in the propane or coal is 70 percent efficiency of conversion to steam), the actual energy expenditure is approximately 59,543 BTU's per gallon of anhydrous ethanol equivalent (Table 6). This number seems very high when compared with grain processing and fermentation. According to Geiger et al.(1980), the total energy expended per gallon of anhydrous ethanol equivalent is 25,000 BTU (calculated energy expenditure) when corn is used as the raw material. The primary reason PPW requires higher BTU values is that it contains almost 4 times more moisture than corn. Therefore, a greater total mass is required to produce an equivalent amount Of ethanol. Consequently, a greater total sensible heat is required in the liquefaction step. The liquefaction, accounting for 51 Z 59 Table 6. Calculated Total Energy Input Prior to Distillation Activity Type 1002 Efficiency Energy 702 Efficiency Energy Expenditure BTU/gal Expenditure BTU/gal Grinding 7360.58 7360.58 Liquefaction 24409.58 30584.68 Saccharification 2507.57 3582.24 Fermentation(Batch) 18015.88 18015.88 Total 49293.61 59543.38 60 of the total energy expenditure prior to distillation, required the largest energy expenditure. To Obtain one gallon of anhydrous ethanol one needs 141.76 pounds PPW while for corn only 19 to 22 pounds are required (Geiger 1980). Grinding, liquefaction, saccharification and fermentation requires more energy to achieve complete processing with the higher mass of PPW. The total primary energy expenditure to produce a gallon Of anhydrous equivalent ethanol from PPW at a small scale ethanol research center based on our estimates is the sum Of the BTU/gal used during processing and fermentation, 59,543 BTU, plus the primary energy expenditure for distillation, 56,578.4 BTU/gal anhydrous ethanol, or a total of 116,121.4 BTU/gal anhydrous ethanol. Krockta (1980) indicated that between 76,000 and 125,000 BTU are required to produce each gallon Of ethanol from potatoes. Our value appears reasonable when compared with the estimate. One gallon Of 100 volume 1 anhydrous ethanol contains 84,378.6 BTU Of usable energy as a fuel (Section 7), while 116,121.4 BTU energy input is required to produce one gallon 95 volume 2 ethanol from PPW. It is evident that the energy required to make ethanol from PPW is higher than the energy obtainable from ethanol combustion. In other words, the energy expenditure required to produce ethanol at the small- scale ethanol production is inefficient. The total energy consumption for processing and fermentation from PPW uses 61 about 70 percent of the obtainable energy from ethanol combustion. The large amount Of energy removed prior to saccharification and fermentation, totaling about 14,000 BTU, illustrates the need for an energy recovery system or heat exchanger to recover the heat from one Operation to another. Proper insulation for the fermentation vessel will substantially reduce the heat losses through convection and radiation during liquefaction, saccharification and fermentation. (b) Continuous Fermentation Based on the continuous fermentation results, the minifermentor reached steady state. It produced 1.28 ml Of pure anhydrous ethanol per hour. The 1.28 ml anhydrous ethanol could produce 28.5 BTU combustion heat. The energy requirement of running the continuous fermentation in minifermentor at steady state per hour was 33.8 BTU. TO produce one gallon anhydrous ethanol about 100,000 BTU would be required; this does not include the enzyme hydrolysis pretreatment and distillation energy expenditures for PPW. It is Obvious that the energy expenditure required to produce ethanol at the mini-scale continuous fermentation system is inefficient. The ethanol productivity Of continuous fermentation could be increased through raising the yeast concentration in the fermentor (Rosario et al., 1979). In addition, scale-up of the continuous fermentation might increase the productivity Of ethanol production and 62 save energy input. A.mu1titude Of Operational parameters need be further examined and Optimized simultaneously. In general, a continuous fermentation system is more efficient (ethanol produced/unit of energy expended) than a batch system. This was not evident in the given case. However, this may have been due to the small scale Of the continuous system. The results from the batch system indicate that the continuous system should have potential as an efficient process of converting PPW to ethanol. (c) Distillation The distillation of 95 volume 2 ethanol from PPW mash uses about 67 percent Of the obtainable energy from ethanol combustion. The feasibility Of small scale fermentation ethanol production is highly dependent on the efficency of the distillation process. Geiger et a1. (1980) reported that production of 95 volume 2 ethanol overheads product from one large column would require 42,971.0 BTU/gal anhydrous ethanol. This value includes a 23 percent loss of heat to the atmosphere and no energy recovery systems in the process. S.E.R.I. (1980) estimated that 39,560 BTU/gal anhydrous ethanol was required tO distill a 95 volume 2 overhead product in a 25 million gallon per year plant using nO energy recovery system. Raphael Katzen (1979) estimated a 50 million gallon per year plant, with an extensive energy recovery system, would utilize 18,140 BTU/gal anhydrous ethanol to distill to 100 volume 2 ethanol product. This is 63 a 54 percent saving over the S.E.R.I. value Of 39,560 BTU/gal anhydrous ethanol but it must be emphasized that the Raphael Katzen value is the result Of a calculation based on a plant Of sophisticated design. It is evident that increasing the efficiency of the distillation column, insulating all hot surfaces and using heat exchangers for recovery Of heat from hot existing streams should save a great deal Of energy for ethanol distillation or production. In addition, new technologies such as solvent or membrane extraction for separating ethanol from water solutions may soon significantly lower the energy input required for producing ethanol by fermenting PPW. Also, it was found that the potato processing A eration produced a great deal Of waste processing energy which can supply the alcohol production process with energy, thereby saving an additional energy input for ethanol production (Christensen and Gerick 1980). SUMMARY AND CONCLUSIONS This study indicated that an average of 36.7 percent (w/w) of total incoming raw material is lost as waste in a small scale potato processing plant (which processes 5 - 6 hundred thousand pounds potato each day). The scrubber loss (89 percent moisture content and starch of 11-58 percent d.b.), trimming loss (79 percent moisture content and starch of 61 percent d.b.), sizer loss (82 percent moisture content and starch of 58 percent d.b.) and miscellanelous (86 percent moisture content) constituted the final hopper constituents. The peel loss, which contained the greatest share Of waste (34 percent of total waste; 83 percent moisture content and starch Of 18.7 percent d.b) was not included in the final hopper due tO its high concentration of lye (NaOH), which made it unfit for yeast fermentation. The potato processing waste (PPW) from the final hopper, representing 59.3 percent Of total waste and 76 percent of total starch , was used as feedstock for the production of ethanol by fermentation. Thermostable commercial enzymes, TARA-THERM and Diazyme L-100 were used to convert starch and polysaccharides in waste tO monosaccharides. The high temperature system ( 90 C in liquefaction and 60 C in saccharification ) was employed in enzyme hydrolysis steps to achieve a high rate of starch tO sugar and to eliminate microorganisms in the 64 65 feedstock which saved processing time and increased the substrate available for yeast fermentation. The completely converted potato processing waste contained 13 to 16 percent fermentable sugar, and the final ethanol concentration Of 7.8 to 9 percent (v/v) was produced by Red Star DADY (distiller's active dry yeast). In terms Of ethanol production from potato processing waste, 1 gallon of anhydrous ethanol required 141.76 lbs of PPW based on batch fermentation data. The total primary energy expenditure to produce a gallon Of anhydrous equivalent ethanol from PPW in a small-scale ethanol research center based on these estimates is the sum of the BTU/gal used during processing and fermentation, 59543 BTU, plus the primary energy expenditure for distillation, 56,578.4 BTU/gal anhydrous ethanol, for a total of 116,121.4 BTU/gal anhydrous ethanol. This is a rather inefficient process in light of fact ethanol that contains only 84,378.6 BTU/gal. Extensive energy recovery systems, insulation and increased capacity could potentially reduce the primary energy input per gallon of ethanol. With the continuous fermentation, 1.28 ml of pure anhydrous ethanol were produced per hour at Optimum flow rate. The 1.28 ml anhydrous ethanol will produce 28.5 BTU combustion heat. The energy requirement Of running the continuous fermentation in minifermentor at steady state was 33.8 BTU/hour; this does not include the enzyme hydrolysis 66 pretreatment and distillation energy expenditures for PPW. The energy expenditure required to produce ethanol at the mini-scale continuous fermentation system used in this study did not give a positive energy balance. Scale-up of the continuous fermentation might increase the productivity Of ethanol production and save energy input. Operational parameters (such as flow rate, fermentor working volume etc.) need to be further examined and optimized simultaneously. Without question, the availability Of conventional fuels will continue to decrease in the future. It is possible that ethanol could assist in making up that deficit. The production Of alcohol from waste material appears to provide the necessary economic stability that is needed to gain investor interest. A singificantly amount of ethanol could be produced from PPW which could supply a source of energy while lowering the cost of disposal. Future Research Needs: (1) The peeling Operation generated the greatest amount Of waste which contained high percentage cellulosic materials. Methods of utilizing the peel slurry waste and efficiently converting cellulosic material to ethanol should be investigated. (2) Research should be done to improve the microbiologial systems of existing hydrolysis and fermentation processes, especially the emerging technology in (3) (4) (5) 67 genetic engineering Of microorganisms which incorporate hydrolysis gene in bacteria and yeast to produce one- step hydrolysis and fermentation process. Investigate the feasibility of recovering heat prior to saccharification and fermentation from one Operation to another by using heat exchanger. Improve distillation processes by changing the Operating parameters of the system or adding liquid/liquid extraction, membrane separation, and liquid- and vapor- phase adsorption processes in fermentation and distillation system. Determine the possibility of combining potato processing waste with waste products from fruits such as apples and grapes, and waste product from dairy products such as cheese whey for ethanol production. APPENDICES 68 MODE I. Beer Stripping r_--—9 65'Vol z Ethanol + Water l (Mode ll Feed) Fermentation I Beer l0 wt 2 Solid§*"17 l 9 vol % Ethanol 1 j ------- :580ttoms Product (Recycle to Hashing Operation) MODE III. Ethanol Rectifying. .F——————7 95 vol % Ethanol + Water 85 vol % Ethanol-————-> + Water 80 vol % Ethanol + Water F——————> (Recycle to Mode 11 feed) Appendix I Modes of Operation for Small-Scale Distillation Column. 69 Appendix II. Thermal Energy Input Calculation for Processing and Fermentation of PPW (l) Grinding (220 volt X l9.6 amp X 0.5 hours) X 3.4l4 BTU/hr —w = 7360.58 BTU (2) Enzyme Liquifaction PPW Specific Heat Calculation: pr = 0.5 XF + 0.3 X5 + l.0 XM PPW contain negligible fat, 20% solid, 80% water pr = 0.3 BTU/lb.F X 0.2 + l.0 BTU/lb.F X 0.8 = 0.86 BTU/lb.F Total Sensible Heat (Qt) Calculation Qw = Mw pr (TL - Tref) (l4l.76 lb) (0.86 BTU/lb.F) (1940F - 68°F) 1536l.ll BTU Qf = Mf Cpf (TL - Tref) = (33 16) (0.21 BTU/lb.F) (l94°F - 68°F) = 873.l8 BTU Qt = Qw + of 1536l.ll BTU + 873.l8 BTU l6234.29 BTU Convective Heat Losses (8) Vertical Cylinder GrL = g B (Tsh -I.Ll L3 2 U where = Kinematic viscosity for air = 20.76 X 10‘5 GrL = (9,8 m/Sz) (1/293 K") (363°K - 2930K) (im)3 (20.76 x10"6 m2/5)2 Gr = 5.43 x 109 7O NuL = C (GrL . prL)m where C = 0.02l, PrL = 0.697, m = 2/5 NuL = 0.021 (5.43 x 109 x 0.697)2/5 1.42 x 102 where K = 0.03003 for air at 3630K hc = 142 x 102 x 0.03003 = 4.26 (W/mz . C) 1 ch = hc A (Tsh - Tco ) where A = n dL = n (0.35 m x 1 m) = 1.099 m2 ch = (4.26 w/m2 . 00) (1.099 m2) (9000 - 20°C) 327.72 w lllB.5 BTU/hr = l677.78 BTU/9O mins. (0) Top Horizontal Plate Grd = 49 s (Tsh - 1..) (0.90) 3 .,2 (9.3 m/Sz) (1/293 K“) (363°K - 2930K) (0.9 x 0.35m)3 (20.76 x 10"6 mé/S)2 1.698 x 108 NUd = C (Grd . Prd)m "here C = 0-15 . Prd = 0.697, m = 1/3 Nud = 0.15 (l.698 x 108 x 0.69711/3 73.6 hC = where th = QCd = where QCd = 0c Nud K (0.9 'd) K = 0.03003 for air at 3630K 73.6 x 0.03003 = 7.02 (w/m2 - 00) 0.9 x 0.35 th ‘ A (TSh - Tm ) A = n (0/2)2 = n (0.35 m/2)2 = 0.096 m2 (7.02 w/m2 - 0C) ( 0.096 m?) (9000 - 2000) 47.17 H 161.0 BTU /hr = 241.5 BTU/90 mins. = QCV + ch = 1677.78 BTU + 241.5 BTU = 1919.29 BTU Radiative Heat Losses (3) hr = where hr Qr where Dr Sacch 0.0069€.(0/100)3 e = 0.94 e = (654 OR + 528 °R)/2 = 591°R 0.069 (0.94) (591/100)3 1.34 (BTU/hr ft? 0F) hr - A (Tsh -'ra) A 1rdL +1r(d/2)2 12.86 (ft?) (1.34 BTU/hr - ft? - 0F) (12.86 ft2) (1940F - 68°F) 2171 BTU/hr 3256 BTU/90 mins. arification Convective Heat Losses (a) GrL Vertical Cylinder = g Bush-1..)L3 U2 (b) where = Kinematic viscosity for air = 18.8 X 10"6 m2/S GrL = (9.8 m/SZ) (1/2930K“) (3330K - 2930K) (1m)3 :6 2 *2 (18.8 X 10 m /S) = 3.785 x 109 NuL = C (GEL . prL)m where C = 0.021, PrL = 0.7025, m = 2/5 NuL = 0.021 (3.785 x 109 x 0.7025)2/5 123.6 hC = NUL . K L where K = 0.0281 for air at 3330K hc = 123.6 x 0.0281 = 3.47 (w/m2 . C) T ch = be A (Tsh - T0° ) where A = fl dL = 1.099 m2 0cv = (3.47 w/m2 . 00) (1.099 m2) (60°C - 20°C) = 152 w = 521.2 BTU/hr = 781.8 BTU/90 mins. Top Horizontal Plate Grd = g 8 (Tsh - TqL) (0.9d)3 U = (9.8 m/SZ) (1/2930x“) (333°K - 2930K) (0.9 x 0.35 m)3 (8.8 x 10‘6.m2/5)2 = 1.18 x 108 73 Nud = 0 (0rd - 9rd)m where C = 0.15 , m = 1/3, Prd = 0.7025 Nud = 0.15 (1.18 x 108 x 0.7025)l/3 = 65.4 hcd = Nud ' K (0.98) where K = 0.0281 for air at 3330K = 5.83 11 C‘ U) hcd 0.0281 x 0.35 ch = hcd - A (Tsh - Ten) where A = K (‘12)2 = 0.0961112 ch = (5.83 181112 - 0C) (0.096 m?) (60°C - 20°C) = 22.39 N = 76 BTU/hr = 114.67 BTU/90 mins. QC = ch + ch = 781.8 BTU + 114.67 BTU = 896.47 BTU Radiative Heat Losses (4) hr = 0.0069 E(9/1oo)3 where = 0.94 e = (600 °R + 528 °R)/2 = 564°R hr = 0.069 (0.94) (564/100)3 = 1.16 (BTU/hr - ft? °F) 0r=hr°A(Tsh-Toe) where A = 12.86 ft? 0r = (1.16 BTU/hr - ft? - 0F) (12.68 ft?) (140°F - 68°F) = 1074.06 BTU/hr 1611.1 BTU/90 mins. Batch Fermentation The total electrical usuage was calculated as follows: (220 volt X 1 amp X 24 hr) X 3.414 BTU/hr ' watt = 18015.88 BTU BIBLIOGRAPHY BIBLIOGRAPHY Aiba, S., Shoda, M., and Nagatani, M. 1968. Kinetics of product inhibition in alcohol fermentation. Biotechnol. Bioeng., V01. 10. Pp. 845-867. Aiba, S., and Shoda, M. 1959. J. Ferment. Technol. Jpn., 47,790. Andreasen, A. A., and Stier, T. J. B. 1954. Anaerobic nutrition of Saccharomyces cerevisiae. J. Cell. Comp. Physiol., 43,271. AOAC. 1975. "Methods of Analysis of the Association of Official Analytical Chemists," 12th Edition.. Washington, D.C. Bazua, C. 0., and Wilke, C. R. 1977. Ethanol effects on the kinetics of a continuous fermentation with Saccharomyces cereevisiae. Biotechnology and Bioengineering Symposium NO. 7, 105-118. Charm, S. E. 1971. The Fundamentals of Food Engineering, 2nd Edition. AVI Publ. co., Westport, CN. Chen, S. L. 1981. Optimization Of batch alcohol fermentation of glucose syrup substrate. Biotechnol. and Bioeng. Vol XXIII. Pp. 1827-1836. Christensen, 0. R., and Gerick, J. A. 1981. Alcohol production from food processing wastes. J. Food Processing, Vol. 42. Pp. 86. Cysewski, G. R., and Wilke, C. R. 1976. Utilization of cellulosic materials through enzymatic hydrolysis I. Fermentation of hydrolysate to ethanol and single cell protein. Biotechnol. Bioeng., 18, Pp. 1297. Cysewski, G. R., and Wilke, C. R. 1977. Rapid ethanol fermentation using vacuum and cell recycle. Biotechnol. Bioeng., 19, Pp. 1125. Cysewski, G. R., and Wilke, C. R. 1978. Process design and economic studies of alternative fermentation methods for the production Of ethanol. Biotechnology and Bioengineering. V01. XX Pp. 1421-1444. Dimler, R. J. 1964. Determination Of optical rotation, for determination of concentration and starch content in corn. Methods Carbohydrate Chem. 4, 133-139. DOE newsletter. 1980. "Alcohol Fuels Process R/D Newsletter." Produced for the United States Department Of Energy by the Solar Energy Research Institute. Winter 1980. Earle, R. L. 1966. "Unit Operations in Food Processing." Pergamon Press, New York. Eveleigh, D. E. 1981. The microbiological production of industrial chemical. Science, Vol. 216. Pp. 155-178. Geiger, J. W. 1980. Design, Operation and Construction of a Distillation Column for a Small-Scale Fermentation Ethanol Plant. Ph.D. dissertation. Michigan State University. Gottschalk, 6., and Starr, M. P. (Editor). 1978. "Bacterial Metabolism.” Springer-Verlag New York Inc., New York. Gray, W. D. 1941. Studies on the alcohol tolerance of yeast. J. Bacteriology. 42:561. Gray, W. D. 1945. The sugar tolerance of four strains of distiller's yeast. J. Bacteriology. 49:445. Heldman, D. R. (Ed.) 1979. Food losses and wastes in the domestic food chain of the United States. Final Report for NSF Project DAR 76-80693. Herbert, 0., Elsworth, R., and Telling, R. C. 1956. The continuous culture of bacteria: A theoretical and experimental study. J. Gen. Microbiol. 14:601-622. Holman, J. P. 1976. "Heat Transfer," 4th Edition. McGraw-Hi11 Book Co., New York. Holme, T. 1962. Biological aspects Of continuous cultivation of microorganisms. In Advances in Applied Microbiology, V01. 4, Academic Press, New York, Pp. 101-116. Holzberg, 1., Finn, R., and Steinkraus, K. 1967. A Kinetic study Of the alcohol fermentation Of grape juice. Biotechnol. Bioeng. V01. 9. Pp. 413-427. Ingram, M. 1955. An Introduction to the Biology Of Yeasts, Sir Isaac Pitman and Sons, London. Jenkins, 0. M. 1981. Gasohol: Outlook for production. American Association of Cereal Chemist. November, 1981. Josalyn, M. A. 1970. "Methods in Food Analysis." Academic Press, New York and London. Krochta, J. M. 1980. Energy analysis for ethanol from biomass- 1980 update. Proceeding Of biomass Alcohol for California: A Potential for the 1980's. University Of California, Davis. Leite, E. F., and Uebersax, M. A. 1979. Losses during the processing of potato products. In “Food Losses and Wastes in the Domestic Food Chain of the United States,” Final Report for NSF:DAR 76-80693. Lemmel, S. A., Heimsch, R. C., and Edwards, L. L. 1978. Optimizing the continuous production Of Candida utilis and Saccharomycopsis fibuliger on potato processing wastewater. Applied and Environment Microbiology, Feb. 1979, Pp. 227-332. Malek, 1., and Ricica, J. 1969. Continuous cultivation Of microorganisms. Folia microbio. 14:254-278. Marth, E. H. 1978. “Standard Methods for the Examination of Dairy Products“, American Public Health Association. Washington, DC. Miller, D. L. 1975. Ethanol Fermentation and Potential. Biotechnology Bioengineering Symposium NO. 5, 345-352. Monod, J. 1949. The growth of bacterial cultures. Ann. Rev. Microbiol. 3:371. Nagodawithana, T. A., and Steinkraus, K. H. 1976. Influence Of the rate Of ethanol production and accumulation on the viability of Saccharomyces cerevisiae in rapid fermentation. Applied and Environmental Microbiology, V01. 31, Pp. 158-162. Priester, Jr. L. E. 1980. Basic ethanol production. Alcohol fuel information booklet for producers. Alcohol Fuel Council -- Governor's Division of Energy Resources, Columbia, South Carolina. Ramalingham, A., and Finn, R. K. 1977. The vacuferm process: A new approach to fermentation alcohol. Biotechnol. and Bioeng. V01. XIX Pp. 583-589. Ranganthan, 8., and Bhat. J. 1958. Ethanol tolerance Of some yeasts. J. Ind. Inst. Sci. 40:105. Raphael Katzen Associates. 1979. Grain motor fuel technical and economic assessment study. U.S. Department of Energy. Rosario, E. J., and Lee, K. J., and Rogers P. L. 1979. Kinetics Of alcohol fermentation at high yeast levels. Biotechnol. Bioeng. Vol. 21. Pp. 1477-1482. S.E.R.I. 1980. Fuel from forms: a guide to small scale ethanol production. Dept. of Energy, Washington, DC. 20545 SP - 451-519. Schwimmer, S., and Burr, H. K. 1967. “Structure and Chemical Composition of the Potato Tuber,“ in “Potato Processing“ Talburt and Smith (Editor) AVI Publ. Co., Westport, CN. Shirzai, A. 1979. Water conservation and pollution reduction during potato processing. M.S. thesis, Michigan State University. Talburt, W. F., and Smith, 0. (Editors). 1975. “Potato Processing.“ AVI Publ. Co., Westport, CN. Tempest, D. W. 1970. The continuous culture of microorganisms. lzTheory Of chemostat. In J. R. Norris and D. W. Ribbons (Eds.), Methods in Microbiology, Vol. 2, Academic Press, New York, Pp. 259-276. Weber, G. M., 1980. Evaluation Of yeast strains suitable for ethanol production. M.S. thesis, Michigan State University. Wilke, C. R., and mairorella, B. 1981. High productivity anaerobic fermentation with dense cell culture. Advance in Biotechnology, Vol. 1 Pp. 539-545. HICHIGRN 13122 STATE UNIV. 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