This book concentrates on biofuels and specifically on ethanol within the United States (US), though in the concluding chapter the author expands the discussion to include other agro-based fuels. The focus reflects current production realties. According to the Renewable Fuels Association, some 168 ethanol distilleries in the U.S. produced more than 9.2 million gallons of ethanol in 2008 (up from 6.5 million in 2007). Biodiesel production in the U.S., by comparison, was approximately 492 million gallons in 2007. In a global context, over 16 billion gallons of ethanol were produced world-wide in 2008 compared to approximately 1 billions gallons of biodiesel. Because of this, "biofuel" overwhelmingly means, and will continue to mean for some time, "ethanol" within not only the U.S. but throughout much of the world.