Fermentation Ethyl DWIGHT L. MILLER Northern Regional Research Center. U.S. Department of Agriculture, Peoria, Illinois 6160l>t Ethyl alcohol is produced in the United States by two major procedures, fermentation and chemical synthesis. Practically all current industrial ethyl alcohol is manufactured synthetically from petroleum and natural gas. All beverage alcohol is 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. It is technically feasible to produce fermentation alcohol from practically any raw material high in carbohydrates and from high cellulose materials such as wood, crop residues. and cultivated fiber crops. Competitive economics have determined the basic raw material. For decades, cereal grains, molasses, and other materials high in starch or sugars have been raw materials for the production of ethyl alcohol through fermentation. Costs for alcohol production based on corn and wheat versus production from ethylene are shown in Tables I-III. The effects of grain prices and ethylene prices on alcohol cost is also shown (Tables IV-VI). These costs have been calculated from previous studies to reflect the inflation rate of the past few years. It is shocking to note the substantial increases in costs which have occurred. The future prices of both grains and ethylene remain to be resolved. There are some predictions that ethylene prices will go to at least 15c/ Ib relatively soon and could increase to as much as 50.20/lb within the next five years. Corn has varied from about 51.00 per bushel to over 54.00. The current price is in the 52.50 to 53.00 per bushel range. The use of food and feed grains for the production of such industrial products as ethyl alcohol may be controversial, but that subject is outside the scope of this report. The United States can normally produce 30i Biotechnol. & Bioeng. Syrup. No.6. 30i-312 (19i6) 19i6 by John Wiley & Sons. Inc.
TABLE I Fermentative Conversion Cost of 190 0 and 200 0 Proof Ethyl from Corn (Exclusive of Cost of Corn) Cents/Gallon 190 0 Proof (2.82 gallons/bushel) Base conversion cost Depreciation ($1.95 million/year, 10 years, 17.7 million gallons) 44.2 11.0 55.2 By-product feed credit (6.8 pounds/ gallon alcohol at $loo/ton) Net 34.0 21.2 200 0 Proof (2.7 gallons/bushel) (1.048 gallons at 21.2 cents/ gallon) 22.2 Cost of dehydration Total cost (exclusive of corn, profit, packaging, and sales expenses) 25.4 TABLE II Fermentative Conversion Cost of 190 0 and 200 0 Proof Ethyl from Wheat (Exclusive of Cost of Wheat) Alcohe>l Cents/Gallon 190 0 Proof, (2.72 gallons/bushel) Base conversion cost Denrecietion ($1.95 million/year, 10 years, 17.2 million gallons) 45.1 11.4 56.5 By-product feed credit (6.5 pound/ gallon alcohol at $loo/ton) Net 24.0 200 0 Proof, (2.6 gallons/bushel) (1.048 gallons at 24.0 cents/gallon) 25.2 Cost of dehydration Total cost (exclusive of wheat, profit, packaging, and sales expenses) 28.4 308
TABLE III Conversion Cost of 190 0 and 200 0 Proof Ethyl from Ethylene (Exclusive of Cost of Ethylene) 190 0 Proof, Base conversion cost Depreciation ($4.0 million/year, 10 years, 50 million gallons) 18.9 8.0 Net 200 0 Proof, AJ.cohol AJ.cohol (1.048 gallons at 26.9 cents/ gallon) Cost of dehydration Total cost (exclusive of ethylene, profit, packaging, and sales expenses) 28.1 3.2 31.3 TABLE IV Effect of Corn Cost on Ethyl Cost (Basis: 2.7 gal 200 0 Bushel) Proof / orn cost/gallon. Cents Price D-J.she1 Corn Conyersion a Total Bese Cost b Dollars 1.50 55.5 25.4 80.:; 1.75 64.8 25.4 90.2 2.00 74.0 25.4 99.4 2.25 83.3 25.4 108.7 2.50 92.6 25.4 118.0 3.00 111.0 25.4 136.4 3.50 129.5 25.4 154.9 4.00 148.4 25.4 173.8 a By-product grains credited at S100/ton in conversion cost. b These costs do not include profits. packaging. and sales expenses. 309
310 MILLER TABLE V Effect of Wheat Cost on Ethyl Cost (Basis: 2.6 gal 200 0 Bushel) Proof / Wheat Aloohol Cost/Galloe. Ceets PriceIBushe1 Wheat Conversicna Total Base Cost b Dollars 2.00 77.0 28.4 10;.4 2.50 96.; 28.4 124.7 ;.00 11;.; 28.4 14;.9 ;.;0 1;4.6 28.4 16;.0 4.00 1;4.0 28.4 182.4 4.;0 17;.0 28.4 201.4 ;.00 192.; 28.4 220.9 a By-product grains credited at SIOO/ton in conversion cost. b These costs do not include profits. packaging. and sales expenses. more grains for the foreseeable future than its domestic and current export requirements. Obviously. there is a use for this grain if we fed the world with an unlimited donation program. How this can be done under current economic procedures is outside this work. Except in times of real national emergency. there appears to be little chance in the near future that fermentation ethyl alcohol can be produced at a cost competitive with gasoline for motor fuel use. However. a potential market is the approximately 300 million gallons per year of industrial alcohol now used in the United States annually. This market permits a higher price than current motor fuel prices based on petroleum. There will undoubtedly soon be increased production of fermentation ethyl alcohol to meet the industrial alcohol demand as well as to meet the beverage alcohol demand. Practically all fermentation alcohol now produced in the United States is consumed by the beverage industry. Current technology and economics would indicate that if cereal grains are available for the production of ethyl alcohol it would be more profitable to take this route than to use the sugars derived from cellulose. Based on corn at $2.00 per bushel (56 lb. 14% moisture). sugars derived from cellulose must have a relatively low raw material value in order to compete. A major favorable factor for cereal grains
TABLE VI Effect of Ethylene Cost on Ethyl Cost 190 0 Proof, Ethylene, Cents/Pound., m 5.0 6.0 7.0 8.0 9.0 10.0 ll.o 12.0 13.0 14.0 15.0 ;;;:; Cost/Gallon, Cents s: m..., Z >..., Ethylene 20.0 24.0 28.0 32.0 36.0 40.0 44.0 48.0 52.0 56.0 60.0 0 Z Conversion ~ ~ ~ ~ ~ ~ ~ ~ 26.9 26.9 ~,-,..., Total manufacturing cost/..,.. gallon (exclusive of profit, -< packaging, and sales r expenses) 46.9 50.9 54.9 58.9 62.9 66.9 70.9 74.9 78.9 82.9 86.9 r > 200 0 Proof! Ethylene 21.0 25.2 29.3 33.5 37.6 41.8 45.9 50.1 54.2 58.4 62.5 Conversion.&l 31.3 31.3 31.3 31.3 31.3.&l 31.3.&l 31.3 31.3 Total manufacturing cost/ gallon (exclusive of profit, packaging, and sales expenses) 52.3 56.5 60.6 64.8 68.9 73.1 77.2 81.4 85.5 89.7 93.8 () 0 ::r: 0 r w
312 MILLER is the large credit for the by-products. The approximately 6.8 lb of byproduct feed per gallon of alcohol with its average value of approximately 5.0cjlb helps to defray part of the conversion costs. The conversion of cellulose to sugars and fermentation of the sugars to ethanol is similar to the use of cereal grains. The sugar concentration in the wood hydrolyzate fermentation, under present techniques, would normally be lower or about one-half that of cereal grain mash which is about 12%. Capital investment and processing costs per unit of production would thus be higher. If a significant credit could be obtained from the lignin and nonfermentable materials from the wood hydrolyzate, the economics of the process would be greatly improved. Continued research and development on the conversion of cellulose to sugars, and their recovery and use, is certainly justified. The process development of more efficient processes is also an important part of the overall investigation. Enzymatic conversion and new process techniques as reported by Natick scientists and University of California engineers (Wilke and co-workers) deserve scientific support.