Purdue Recalculates Benefits of Ethanol on Greenhouse Gas Production

Revisions to a Purdue University economic analysis have cut about 10 percent of the total emissions expected from an increase in corn ethanol production. The findings, released in a report to the U.S. Department of Energy's Argonne National Laboratory, show that ethanol could be a somewhat better option than previously thought for reducing greenhouse gas emissions.

Wally Tyner, a Purdue agricultural economist and the report's lead author, said revisions to the Global Trade Analysis Project model better reflect market conditions and land productivity than a 2009 report that showed corn ethanol wouldn't significantly lower greenhouse gas emissions over gasoline.

"This is a new area. We haven't been faced with estimating land-use change related to biofuels ever before," Tyner said. "The difference between this report and previous reports is advances in science. With any issue, your first cut may not be the best, but when you get new data and new methods, you improve."

The report considers land-use changes when calculating total greenhouse gas emissions from biofuels based on the U.S. program to increase corn ethanol production to 15 billion gallons by 2015. Those changes include the emissions created by converting forest or pasture land to cropland. The new analysis predicts emissions related to land-use change at 35 percent lower than previous analyses.

Previous reports estimated that marginal lands converted to corn production would be two-thirds as productive as prime land. The new simulations used data from another model to predict productivity for land being brought into cultivation by country and by agro-ecological zone.

Tyner said the change had a large effect on decreasing the number of acres needed to produce 1,000 gallons of ethanol.

"In Brazil , in particular, the production of the land that would come into use is much better than two-thirds," Tyner said. "It's closer to one, or about as good as current land in use."

The Argonne National Laboratory was the major funder of the new study. Tyner said future simulations would add cellulosic biofuels to the analysis.