Purdue report shows lower ILUC effect

By Luke Geiver | April 15, 2010
Posted May 3, 2010

Purdue University has released a study on indirect land use change, reporting a 10 percent lower GHG emission rate from corn ethanol production than a previous report. The study, "Land Use Changes and Consequent CO2 Emissions due to US Corn Ethanol Production: A Comprehensive Analysis," was headed by Purdue University agricultural economics professor Wallace E. Tyner, and completed in conjunction with the U.S. DOE's Argonne National Laboratory. Through revisions to the Global Trade Analysis Project, the reduced GHG level is now considered more accurate due to updates on market conditions and land productivity, said Tyner.

"We should from the outset acknowledge that land use change is a complicated process. It is driven by many factors and varies through time," the study said. "There are social as well as economic factors involved in the complicated process of evolving land use. The factors vary by culture, region, and economy. Obviously neither this analysis nor any analysis can capture all the factors involved in land use change."

The new study used three GTAP simulations. Starting with economic data from 2001, followed by data through 2006, the study also included data from 2006 through 2015 that considered population growth and crop yield. According to Tyner, the third simulation from 2006-2015 represents the most accurate simulation, providing a number that indicates corn ethanol creates 77.5 grams of CO2 emissions per megajoule, down from the 2009 report that indicated ethanol CO2 emissions equaled 86.3 grams. The report also calculates the land needed to produce ethanol. In 2009, 0.27 hectares (ha.) per 1000 gallons of ethanol was required, while the 2010 report shows only 0.12 ha./1000 gallons.

"We have better data on land productivity and on cropland pasture and CRP lands, and these data and associated parameters are now in the model. We have improved the treatment of the livestock and livestock feed sectors. Similarly, these changes are reflected in the current version of the model," the study said. "We have amassed data on crop yields and many other variables for every region of the world and used much of that data in our analysis and model calibration. These data and model improvements have significantly improved the analysis and model results."

One main factor for the new results stems from new assumptions in the GTAP system. In previous reports, marginal land conversion rates were only considered to be two-thirds as productive as prime land. The 2010 version shows that many areas, mainly in Brazil and roughly 60 million acres in the U.S., are actually more productive than first estimated. Tyner said the change had a large effect on decreasing the number of hectares of land needed to produce 1,000 gallons of ethanol.

"Ethanol from corn can play a significant role in cleaning the air, creating U.S. jobs and securing our national and economic defense. These results prove that ILUC is a complicated and technical rule that should not determine the full implications for the ethanol industry until we have more detailed, long term studies of the issue," said Tom Buis, CEO for Growth Energy.

Tyner, who is also a member of the California Air Resources Board Expert Working Group, the group assigned the task of assessing ILUC for the California Low Carbon Fuel Standard, said the new Purdue report will be considered before the working group submits a report. The Renewable Fuels Association president, Bob Dinneen, urged CARB to take immediate action. "Time is of the essence," Dinneen wrote in a letter addressed to CARB chair, Mary Nichols. "Adopting the Purdue ILUC value immediately would greatly enhance the ability of regulated parties to meet their greenhouse gas reductions obligations in the early years of the LCFS, ultimately minimizing fuel cost impacts to the state's consumers."

View the study at: http://www.transportation.anl.gov/pdfs/MC/625.PDF