Biofuels are liquid fuels produced from biomass materials and are used primarily for transportation1. The term biofuels most commonly refers to ethanol and biodiesel. In 2007, the United States consumed 6.8 billion gallons of ethanol and 491 million gallons of biodiesel. By comparison, 2007 consumption of motor gasoline and diesel (not inclusive of biofuels) was 139 billion gallons and 39 billion gallons, respectively.