University of Minnesota Professor David Tilman, Princeton University Visiting Scholar Tim Searchinger, Dartmouth Professor Lee Lynd and others involved in the debate over the environmental and social impacts of biofuels have published in Science magazine  what amounts to a new manifesto on how biofuels can be done right. The authors list five biofuel feedstocks that are the best in terms of sustainability -- "lower life-cycle greenhouse-gas emissions than traditional fossil fuels and with little or no competition with food products." The authors conclude:
Three steps should be taken: meaningful science-based environmental safeguards should be adopted, a robust biofuels industry should be enabled, and those who have invested in first-generation biofuels should have a viable path forward.
The EPA's proposed rule on the Renewable Fuel Standard was intended to outline a viable path forward for first-generation biofuels. The Best Case Natural Gas Dry Mill, the Biomass Dry Mill, and the Biomass Dry Mill with Combined Heat and Power scenarios outlined in the "EPA Lifecycle Analysis of Greenhouse Gas Emissions from Renewable Fuels"  all produce reductions in greenhouse gases that come close to or exceed the 20 percent standard in the RFS. The EPA's definition of the Best Case is: "Best case plants produce wet distillers grain co-product and include the following technologies: combined heat and power (CHP), fractionation, membrane separation and raw starch hydrolysis." The question will be whether anyone invests in these technologies or in additional biofuel production at all, given the current economic and social climate in which biofuel companies are operating. One possible factor in choosing the best biofuels ought to be how soon they can become a reality and whether they can be improved from there.