Groups urge EPA to adopt GREET, improve GHG modeling of biofuels

By Erin Voegele | April 04, 2022

Representatives of the U.S. ethanol industry urging the U.S. EPA to improve its greenhouse gas (GHG) modeling of corn ethanol and other biofuels by adopting the U.S. Department of Energy’s GREET model and using updated, transparent sources of data.

The EPA on Feb. 28 through March 1 hosted a virtual public workshop on GHG modeling for biofuels in an effort to solicit information on the current scientific understanding of GHG modeling of land-based crop biofuels used in the transportation sector. The agency said information gathered through the event and an associated written comment period will be used to inform a range of current and future actions, including the EPA’s methodology for quantifying GHGs under the Renewable Fuel Standard.

The Renewable Fuels Association, the American Coalition for Ethanol and Growth Energy are among the organizations that participated in the workshop and submitted written public comments ahead of an April 1 deadline.

In its comments, the RFA stressed the importance of using updated and transparent data, a level analytical playing field, and state-of-the-art modeling tools when conducting lifecycle analysis.  

“RFA commends the EPA for holding the recent workshop and soliciting related comments,” wrote RFA President and CEO Geoff Cooper in a cover letter. “The agency’s last analysis of the GHG emissions associated with corn ethanol was conducted in 2010, as part of the rulemaking process for the RFS after it was revised by the Energy Independence and Security Act of 2007. Over the ensuing 12 years, the RFA has consistently urged the EPA to update its analysis to reflect the efficiencies that have been gained in ethanol production and the advances that have been made in lifecycle analysis.”

The RFA also strongly recommends that the EPA adopt Argonne National Laboratory’s GREET model, calling it the “gold standard” of lifecycle models. In addition, the RFA called on EPA to consider significant indirect GHG effects for all fuels, including petroleum.

ACE also called GREET the gold standard in lifecycle GHG modeling and urged the agency to adopt its use. “Unlike EPA’s badly outdated 2010 assessment, the assumptions and estimates used by Argonne scientists in GREET are under constant peer review and updates to the model occur annually,” ACE said in its comments. “Not only do more than 40,000 users around the world depend upon GREET to help determine the lifecycle GHG impacts of certain fuel technologies, but the model is the basis for the assessments used under the California Low Carbon Fuel Standard and Oregon Clean Fuels Program. Legislation pending in Minnesota to create a clean fuel standard would statutorily require the use of the latest GREET model.”

ACE’s comments highlight discrepancies between EPA’s outdated approach to lifecycle modeling and more recent versions of the GREET model. Land use change represents one of the most glaring discrepancies, as EPA’s outdated modeling assigns an enormous land use change penalty of 29 grams to the overall carbon intensity (CI) of corn ethanol and using a recent version of GREET indicates a more accurate land use factor between 3.78 and 7.5 grams.

Growth Energy’s comments also urge the EPA to update its lifecycle analysis (LCA) of corn ethanol. “Updating the LCA of ethanol is critical not only to faithfully implementing the Renewable Fuel Standard program (the only Clean Air Act program explicitly aimed at reducing GHG emissions), but for sound policymaking on a range of future potential rulemakings designed to facilitate the use of E15, flex fuel vehicles, and use of higher-level ethanol blends like E85, and sustainable aviation fuel (SAF),” Growth Energy wrote. “Robust and accurate cost-benefit analyses depend on accurate assessment of the GHG impacts of biofuels, particularly given utilization of the social cost of carbon (SCC) to monetize the benefits of anticipated GHG emission reductions.” 

All three groups also used the comment period to offer rebuttals to a recent paper published by the University of Wisconsin’s Tayler Lark and others in the Proceedings of the National Academy of Sciences. That paper, titled “Environmental Outcomes of the U.S. Renewable Fuel Standard,” has several fundamental flaws and vastly overstates the impacts of land use change. A recent assessment of the paper by experts at the Department of Energy’s Argonne National Laboratory, Purdue University, and the University of Illinois system revealed major flaws in the study, showing that the authors made unfounded allegations about the GHG benefits of ethanol compared to gasoline.