Cornell ecologist David Pimentel and Berkeley professor of civil and environmental engineering Tad W. Patzek have published a study that shows that, for corn, 29 percent more fossil energy is used in ethanol production, than the energy yielded by the ethanol output. In the Cornell web summary Pimental is quoted as saying: “There is just no energy benefit to using plant biomass for liquid fuel. These strategies are not sustainable.” See: http://www.news.cornell.edu/stories/July05/ethanol.toocostly.ssl.html
Pimentel and Patzek’s study was published in: Natural Resources Research (Vol. 14:1, 65-76).