ETHYL ALCOHOL PRODUCTION FOR FUEL: ENERGY BALANCE.

A net energy analysis model is used to assess the energy balance of fuel ethanol production. The model is based on corn as the feedstock and includes energy inputs for: (a) producing corn on the farm; (b) transporting corn from the farm to the alcohol plant; and (c) the commercial production process. It is assumed that the commercial process produces at least 3.9 x 10/sup 6/ L (1.0 x 10/sup 6/ gal) of ethanol per year. The major products of the production process are ethanol and distillers dry grain and solubles (DDGS). Carbon dioxide released during the fermentation process is not assigned an energy value. Three energy accounting procedures are used in this study. The first one is in terms of total energy inputs and outputs. From this method, alcohol production yields 4600 kJ/L (16,000 Btu/gal) and 2400 kJ/L (8700 Btu/gal) more energy than required to produce it using dryland corn and irrigated corn, respectively. The second method examines the total premium energy inputs and outputs of the boundary, where premium energy is defined as any energy source that is versatile in both its uses and portability, e.g., natural gas, alcohol or petroleum energy sources. This analysis shows that itmore » takes 4900 kJ/L (17,500 Btu/gal) and 7,100 kJ/L (25,400 Btu/gal) more premium energy to manufacture alcohol than the premium energy yielde. The third method assumes that, of the energy inputs on the farm, off-farm transportation and the alcohol plant, 35%, 0%, and 85%, respectively, could, conceivably, be replaced by non-premium sources of energy. With this analysis, ethanol is a net premium energy producer; 15,200 kJ/L (54,400 Btu/gal) and 13,800 kJ/L (49,400 Btu/gal) more premium fuel is produced than is required for dryland corn and irrigated corn, respectively. This results in a net premium fuel gain of 2.8 for dryland corn, and 2.4 for irrigated corn.« less