Ethyl alcohol (or ethanol, grain alcohol, or C2H5OH) is a colorless, sweet-smelling substance. Ethanol production in the form of intoxicating beverages was one of humankind's earliest industrial achievements. Beyond being the key ingredient in alcoholic drinks, ethanol is a solvent and has a growing role as a renewable-source fuel for motor vehicles.
Ethanol can be made synthetically by catalytic reaction of ethylene (from natural gas) with steam. However, most ethanol is made by fermentation of plant material. In fermentation, single-celled yeast organisms consume simple sugars, excreting ethyl alcohol and carbon dioxide. Plants are composed of carbohydrates (compounds containing carbon, hydrogen, and oxygen), and the simple sugars (called monosaccharides) are building blocks for complex carbohydrates like starches, higher sugars, and cellulose. Fruits tend to be rich in sugar, and grains are rich in starch, while straw and wood are dominated by cellulose. Only the monosaccharide sugars are directly fermentable, so natural fermentation requires a sugarrich fruit (like grapes) for significant alcohol content. To make ethanol from other biomass sources, higher-order plant structures must be broken down to monosaccharides. Specialized enzymes or weak acids are used to break starch and cellulose into monosaccharides before fermentation. After fermentation, the resulting "beer" solution contains a small percentage of ethanol. Solids are filtered out for use as animal feed or fuel, and ethanol is separated from the remaining water by distillation and mole sieve techniques. Ethanol processes are well established for grain feed stocks, and research is improving ethanol yield and energy e.ciency. New processes and enzymes are being developed to enable commercial production from cellulosic materials such as grass, straw, and wood.
Fuel ethanol is denatured by blending it with 5 percent gasoline or solvent to render it undrinkable. The denatured product is then blended with petroleum-based gasoline as a high-octane fuel component. American gasoline contains up to 10 percent ethanol, especially in winter months and in areas with serious air pollution. e85 (gasoline with 85 percent ethanol) is used in specially adapted or "flex-fuel" vehicles. The 15 percent hydrocarbon content in e85 is tailored to optimize fuel volatility and inhibit corrosion.
In 2000 American ethanol production was 1.8 billion U.S. gallons with roughly equal amounts used for fuel and for all other purposes. About 7 percent was synthetic, and the rest was the result of fermentation. Of the fermentation ethanol, 90 percent used corn as a feedstock, with the dominant production in Corn Belt states (Illinois, Iowa, Nebraska, and Minnesota). Overall, the Great Plains states supplied 23 percent of American fermentation ethanol. Canadian ethanol production in 2000 was in excess of 160 million U.S. gallons, with 75 percent from Ontario corn and 5 percent from forest products. The remaining 29 percent came from wheat, the dominant grain crop in the Prairie Provinces. Raw grain is bulky and expensive to transport, so most ethanol production plants are located in areas of high grain production or along major transportation routes. In 2000 there were two ethanol production plants in the Prairie Provinces– at Lanigan, Saskatchewan, and Red Deer, Alberta–and nineteen such plants in the American Great Plains, with Nebraska, the leading state, with seven.
Concerns over air pollution, petroleum supply, and greenhouse gas emissions are leading to increased production of biologically based ethanol. Currently, this is raising demand for grain, a major product of fertile lands in the Great Plains region. Future growth of the fuel market and commercialization of cellulose-based ethanol processes are expected to create a demand for cellulosic crops such as switch grass, straw, and poplar wood. These crops grow well on less fertile lands, so their production would provide an alternative industry in Plains areas currently dominated by livestock.
M. David Checkel University of Alberta