Ethanol Quick Facts
- In 2005, the U.S. produced about 4 billion gallons of ethanol from corn grain, equaling approximately 2% of the 140 billion gallons of gasoline consumed.
- Ethanol is widely used as a fuel additive. The oxygen contained in ethanol improves gasoline combustibility.
- The Energy Policy Act of 2005 has established a renewable fuels standard which requires using 7.5 billion gallons of ethanol by 2012.
- E85 (85% ethanol and 15% gasoline blend) can be used as a substitute for gasoline in vehicles that have been modified to use E85.
- Energy content of E85 is 70% that of gasoline, so about 1.4 gallons of E85 are needed to displace one gallon of gasoline.
- Starch in corn grain is readily degraded into glucose sugar molecules that are fermented to ethanol. The complex structural carbohydrates in cellulosic biomass are more difficult to break down, and they yield a mix of glucose and other sugar molecules that are not as efficiently converted to ethanol.
- An acre of corn generates about 4.5 tons of grain; 66% (3 tons) is starch that can be converted to 400 gallons of ethanol. Ethanol yield could be increased to roughly 700 gallons per acre by using corn stover (stalks and leaves) in addition to corn grain.
- Potential energy crops include perennial grasses like switchgrass or woody crops such as fast growing poplar. For these crops, average annual yield per acre is about 5 dry tons of cellulosic biomass; at a current conversion rate of 65 gallons per dry ton, an acre generates about 325 of gallons of ethanol. Goals include increasing biomass yield to 10-15 dry tons per acre and ethanol yield to 80-100 gallons per dry ton of biomass.
