Experts with the Department of Energy’s Argonne National Laboratory, Purdue University, and the University of Illinois system have just published an assessment finding major flaws in a recent paper that made unfounded allegations about the greenhouse gas benefits of ethanol compared to gasoline.

Responding to the report Environmental Outcomes of the US Renewable Fuel Standard, which was led by Tyler Lark of the University of Wisconsin, the authors stated, “After a detailed technical review of the modeling practices and data used by Lark et al., we conclude that the results and conclusions provided by the authors are based on several questionable assumptions and a simple modeling approach that has resulted in overestimation of the GHG emissions of corn ethanol.”

Among the “questionable assumptions” in the disputed report:
The land-use changes identified by Lark et al. likely reflect the conversion of fallow or idle land to crops rather than permanent grasslands.
Lark et al. likely overestimated soil organic carbon (SOC) loss by a factor of two to eight as a result of the incorrect application of carbon response functions. The authors noted that “the validation of the SOC emissions model used by Lark et al. … showed remarkably poor fit to measured SOC changes.” This is important, since a foundational assertion in the recent study was that emissions related to land-use change are higher than commonly recognized.
Lark appeared to have double-counted the emissions of nitrous oxide—a greenhouse gas—from the use of fertilizer in corn production by adding them in while overlooking the fact that they are already included in the corn-farming-related emissions in the main lifecycle assessment models.

Renewable Fuels Association President and CEO Geoff Cooper said it is unfortunate that such a flawed report about ethanol made headlines despite its obvious errors. “Now that light has been shown on these flaws, we call on the news media to correct the record—particularly those who were so quick to report this now thoroughly debunked attack. Ethanol is a renewable, domestically produced fuel that is lower in cost and lower in carbon than gasoline. Today more than ever, it’s also vital for energy security.”