Potential U.S. Supply.In 2005, 14.3% of the U.S. corn harvest wasprocessed to produce 1.481010liters of ethanol (20, 21),energetically equivalent to 1.72% of U.S. gasoline usage (22).Soybean oil extracted from 1.5% of the U.S. soybean harvestproduced 2.56108liters of biodiesel (20, 23), which was 0.09%of U.S. diesel usage (22). Devoting all 2005 U.S. corn andsoybean production to ethanol and biodiesel would have offset12% and 6.0% of U.S. gasoline and diesel demand, respectively.However, because of the fossil energy required to produceethanol and biodiesel, this change would provide a net energygain equivalent to just 2.4% and 2.9% of U.S. gasoline and dieselconsumption, respectively. Reaching these maximal rates ofbiofuel supply from corn and soybeans is unlikely because thesecrops are major contributors to human food supplies throughlivestock feed and direct consumption (e.g., high-fructose cornsyrup and soybean oil, both major sources of human caloricintake).