Researchers at the University of Minnesota say a comparative analysis of the life cycles of two popular fuel additives shows that biodiesel has a much higher net energy benefit than ethanol, but neither can do much to meet growing U.S. energy demand. The study (Proc. Natl. Acad. Sci. USA 2006, 103, 11206) concludes that both corn-grain-derived ethanol and soybean-based biodiesel produce more energy than is needed to grow the crops; however, the amount of energy each returns differs greatly. Biodiesel returns 93% more energy than is used to produce it, whereas ethanol currently provides only 25% more energy, according to the study. The researchers caution that neither biofuel can come close to meeting the growing demand for alternatives to petroleum. Converting all current U.S. corn and soybean production to biofuels would satisfy only 12% of gasoline demand and 6% of diesel usage. Meanwhile, global population growth and increasingly affluent societies will increase demand for corn and soybeans for food. The study points to nonfood plants such as prairie grasses and woody plants, which can grow on marginal lands with minimal input of fertilizers and pesticides, as well as agricultural and forestry wastes, as the best hope for biomass-based energy.