Important Biofuels Study Published
July 21st, 2006,On May 12 I reported on a talk on biofuels given by Dr. Stephen Polasky of the University of Minnesota. Now Polasky and several others, including renowned biologist David Tilman, have published their findings in an important paper titled “Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels,” published online July 12 in the Proceedings of the National Academy of Sciences. Jason Hill, formerly of the St. Olaf College biology department, also participated in the study.
I haven’t yet been able to access the full article, but judging from the abstract, it appears likely that the study will have important implications.
The study used “life-cycle accounting” to determine that ethanol (made from corn) yields 25% more energy than was used in its production, while biodiesel (made from soybeans) produces an energy gain of 93%. Biodiesel also has the benefit of requiring less pesticide and fertilizer. Both fuels significantly reduce pollutants as compared to petroleum-based gasoline, including those pollutants that contribute to global warming, though biodiesel does much better in this respect.
The paper is not sanguine about the prospect of ethanol and biodiesel replacing petroleum. “Neither biofuel can replace much petroleum without impacting food supplies,” it says in the abstract. “Even dedicating all U.S. corn and soybean production to biofuels would meet only 12% of gasoline demand and 6% of diesel demand.”
The authors recommend that we begin to invest in biofuels other than ethanol and biodiesel: “Transportation biofuels such as synfuel hydrocarbons or cellulosic ethanol, if produced from low-input biomass grown on agriculturally marginal land or from waste biomass, could provide much greater supplies and environmental benefits than food-based biofuels.”
Looks like we need to throttle back on ethanol and promote some of these “synfuel hydrocarbons” and “cellulosic ethanol” options. I look forward to learning more about those alternatives.
December 22nd, 2006 at 2:36 pm
[...] I’ve discussed research on biofuels in earlier posts, including one from last summer. Now Prof. David Tilman at the University of Minnesota and others have published another study that demonsrates the advantages of prairie grass over corn as a crop for producing ethanol. Here are some quotes from a December 7 StarTribune story, “Grass beats corn in ethanol study“: University researchers, led by Tilman, think they’ve found a solution — supply the facilities that make ethanol with a diverse mixture of prairie grasses instead of corn. The grasses not only can produce more net energy per acre than corn but they also act as a sponge for greenhouse gases before being harvested, soaking them out of the air and into their roots and surrounding soil, the researchers found. [...]