Petroleum alternatives include renewable fuels such as biodiesel, derived primarily from soybeans, and ethanol, distilled mostly from corn grain. In the first comprehensive analysis of the energy gains and environmental impact of both fuels, University of Minnesota researchers determined biodiesel to be the better choice. Ethanol from corn grain produces 25 percent more energy than all the energy people invested in it, whereas biodiesel from soybeans returns 93 percent more. Compared with fossil fuels, ethanol produces 12 percent fewer greenhouse gas emissions, whereas biodiesel produces 41 percent fewer. Soybeans also generate significantly less nitrogen, phosphorus and pesticide pollution. Dedicating all current U.S. corn and soybean production to biofuels, however, would meet only 12 percent of gasoline demand and 6 percent of diesel demand. Prairie grass may provide larger biofuel supplies with greater environmental benefits, the scientists reported online July 10 via the Proceedings of the National Academy of Sciences USA.