An important new assessment published by experts from the Department of Energy’s Argonne National Laboratory, Purdue University, and the University of Illinois system found 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.”
Renewable Fuels Association President and CEO Geoff Cooper responded to the release of the assessment. “It has been well established that ethanol reduces greenhouse gas emissions by roughly half compared to gasoline. Unfortunately, a recently published report that attacked ethanol made headlines despite its obvious errors,” said Cooper. “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.”
A number of problems with the study by Lark et al. were pointed out, including:
- 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.
- Lark attributed 5.5 billion gallons of ethanol per year to the expanded Renewable Fuel Standard (RFS2) between 2008 and 2016 by comparing the volume under RFS2 and RFS1 without considering other significant drivers of ethanol production.
- The validity of picking the limited time period of 2006-2010 to assess price impacts associated with RFS2 is questionable. This does not align with the 2008-2016 timeframe for the study by Lark et al., and significant price increases occurred during this period.
When the Lark paper was first published, RFA posted a preliminary rebuttal of the effort and noted in a blog post that the association had tried to work with Lark, but to no avail. “We asked how we could work together to ensure their error-ridden satellite analysis of land-use changes was grounded in reality,” Cooper wrote. “We never heard back from them. RFA is always open to having an honest, fact-based discussion about the impacts of ethanol and the RFS on the environment and economy.”