Land-use studies may affect policy

By Anduin Kirkbride McElroy and Marc Hequet | April 08, 2008
New discussion on the indirect impacts of land-use change for biofuel crop production may affect how ethanol is legislated, according to Michael Wang of the U.S. DOE's Argonne National Laboratory.

His comments were in response to one of two controversial studies posted on Science magazine's Web site in early February that concluded the growing production and use of biofuels could escalate greenhouse gas (GHG) emissions around the globe.

In a letter to Science, Wang identified shortcomings in the study titled "Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land Use Change," which was written by Timothy Searchinger of Princeton University and others. Wang challenged the assumptions made on corn yield, the amount of ethanol to be produced from corn, distillers grains displacement, U.S. corn export reductions, biomass resources, ethanol production efficiency and potential land-use changes. He also cautioned the scientific community. "While scientific assessment of land-use-change issues is urgently needed in order to design policies that prevent unintended consequences from biofuel production, conclusions regarding the GHG emissions' effects of biofuels based on speculative, limited land-use-change modeling may misguide biofuel policy development," he wrote.

One policy in development that might be affected by this study is California's low-carbon fuel standard, which calls for a reduction of at least 10 percent in the carbon intensity of California's transportation fuels by 2020. The California Air Resource Board is handling that project and will likely use the Greenhouse gases, Regulated Emissions and Energy use in Transportation (GREET) model, which was developed by Wang, to determine the carbon footprint of individual fuels. It includes greenhouse gas emissions from direct land-use changes associated with corn-based ethanol production. Wang admitted that the model needs to be updated to account for "both direct and indirect land-use changes associated with future, much-expanded U.S. biofuel production," he wrote to Science. "Such an effort requires expansion and use of general equilibrium models at the global scale."

Searchinger's study acknowledged that biofuel crop production sequesters greenhouse gases, but counters that previous "analyses failed to count the carbon emissions that occur as farmers worldwide respond to higher prices, and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels." After some entities criticized the study, including the DOE, Searchinger admitted to EPM that his study won't be the final conclusion on the issue. "There are plenty of ways to improve upon our analysis," he said. "However, I don't think the critics have yet found them."

The DOE called Searchinger's assumptions "incorrect or unrealistic" and his data obsolete. The government entity also criticized the second Science study, titled "Land Clearing and the Biofuel Carbon Debt," which was conducted by Joseph Fargione of The Nature Conservancy. The DOE conceded that some of Fargione's points are "irrefutable," such as the negative impacts of clear-cutting rainforest or other carbon-rich lands. "We're not in denial about that," said Zia Haq, senior analyst with the DOE's biomass program. "We just want to address the issue of how much of that deforestation is caused by biofuels rather than other factors (such as timbering and forest fires)."

The University of Minnesota's David Tilman, a key researcher on the second study, contended that his paper is "not controversial in terms of its underlying science." Moreover, it "provides guidance" to help producers comply with the Energy Independence & Security Act of 2007.