Ethanol More Energy Efficient Than Thought

Corn field. Photo by Rene Cerney

Corn-based ethanol, the plant fuel that contributes about 2 percent to the total transportation fuels mix in the United States, is a more energy efficient fuel than previous studies would suggest, according to a new rigorous review reported in Science.

Alexander Farrell and colleagues closely examined six previous studies, two of which found that the energy used to produce ethanol outweighed any energy provided by the fuel. By correcting a number of assumptions and calculations, including the use of outdated information on production methods and the failure to account for the energy benefits of ethanol byproducts, the authors estimate that corn ethanol reduces petroleum use by about 95 percent per gallon of fuel, but only reduces greenhouse gases by about 13 percent. Improved agricultural practices and ethanol made from plants other than corn could boost ethanol’s environmental performance, Farrell and colleagues say.

Dwindling fossil fuel supplies, global warming and economic woes tied in to rising gas prices all point toward the necessity of a biofueled future, according to Arthur Ragauskas and colleagues in this “Review” article. The authors lay out a roadmap for the near future of biofuel production.

To prepare for this future, researchers are at work building a better biorefinery, using genomic tools to boost the yield of fuel crops, applying new chemical techniques to break down and convert the raw material of a biofuel “feedstock” into both fuel and byproducts such as commercially useful plastics and lubricants. Biorefineries could also find ways to recycle their own waste products, the authors say.

In a related “Editorial,” Steven Koonin says biomass can provide a secure fuel supply with lower greenhouse gas emissions while supporting the agricultural economy, without significant changes to our current vehicles or the way we buy fuel.

26 January 2006