Grasses reign among biofuel crops

Ethanol and biodiesel made from a diverse mix of native grassland perennials can provide a net energy gain, greater greenhouse gas reductions, and less agricultural pollution than biofuels made from corn grains or soybeans, according to a recent study (Science 2006, 314, 1598). The report found that native grasses used to make biofuels are carbon-negative, because the carbon they hold in the soil is greater than the carbon released when the plants are grown and harvested and when the grass-based biofuel is refined and burned. Compared with gasoline, corn ethanol and soybean diesel lower greenhouse gas emissions by 12% and 41%, respectively, but they still are net carbon dioxide sources. The report, by economists and scientists at the University of Minnesota, found that a mix of native grasses provides more biomass than other biofuel sources even in poor soil with no energy inputs and without displacing food production or destroying bird and animal habitats. However, the intense energy input used to create ethanol from corn grain leads to a much higher yield of fuel per acre from corn than from prairie grasses.