September 22, 2008 12:00 PM PDT
The question of how much biomass is available to offset petroleum fuel is a subject of intense research. An important Department of Energy-funded report, nicknamed the "billion-ton study," estimated that the United States has enough biomass to make about 30 percent of the country's liquid fuels by 2030. Optimists say that underestimates the positive impact of genetically optimized energy crops.
Cellulosic ethanol is better for the environment than corn ethanol, but naysayers still warn about the impact of biofuels on land use, water, and ecosystems.
Photo by National Renewable Energy Laboratories
Caption by
Martin LaMonica
