News & Ideas

ACE to EPA: Adopt GREET Model and Recognize Ethanol’s Low Carbon Value

The American Coalition for Ethanol (ACE) submitted feedback today to the Environmental Protection Agency’s (EPA) request for comment on the current scientific understanding of greenhouse gas (GHG) modeling of land-based crop biofuels. ACE CEO Brian Jennings and ACE Board Director Ron Alverson contributed to the feedback after attending EPA’s workshop on biofuel GHG modeling. The comments cover subject areas that illustrate why EPA must update the methodology it uses to account for the lifecycle GHG emissions of ethanol and other biofuels to properly credit their GHG benefits to meet climate goals.

The topics covered include: the role corn ethanol can play in combatting climate change; land use change discrepancies, along with research that debunks the flawed Lark et al. study findings and the mythical tie between ethanol and food price increases; why GREET is the gold standard modeling tool and should be adopted by EPA; how efficient use of fertilizer is reducing nitrous oxide emissions; and soil carbon sequestration advances through climate-smart farming. The comments conclude by detailing a first-of-its-kind pilot project ACE is leading to convince market regulators and lifecycle modelers to provide carbon credits for certain farming practices.

“Unlike EPA’s badly outdated 2010 assessment, the assumptions and estimates used by Argonne scientists in GREET are under constant peer review and updates to the model occur annually,” the feedback stated. “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.”

Jennings noted in the comments that a considerable portion of EPA’s GHG modeling workshop was devoted to uncertainty. “EPA should not dwell on uncertainty or allow a particular researcher’s opinion of what is ‘perfect’ be the enemy of the real good the Agency can do by updating its assumptions about the GHG emissions of ethanol and by specifically choosing to adopt the gold-standard model for this purpose: the latest GREET model,” Jennings wrote.

The comments highlight discrepancies between EPA’s outdated approach to lifecycle modeling and more recent versions of the GREET model.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.

The comments further detail how the recent Lark et al. paper wildly overstates land use change and includes a summary of the technical rebuttal from experts at Argonne, Purdue and the University of Illinois that eviscerates both the methodology and flawed findings from the study.

Along with land use change, ACE’s comments reference research that has largely debunked the link between ethanol production and oil prices to food prices, as false narratives have resurfaced given the geopolitical concerns about inflation in general and food prices specially. ACE strongly encourages EPA to heed the finding from Shrestha et al. on the issue, which indicates “that there has been no significant change in U.S. food prices due to biofuels and biofuels have not caused any significant agricultural land use change.”

ACE’s comments also discuss why soil carbon models and the GREET model should be used by regulators such as EPA and the California Air Resources Board to assign credits for climate-smart farming practices that help reduce the overall CI of biofuels. “CARB and other regulators lean on the ‘need’ for localized assessments as an excuse for not providing farm-level carbon credits for biofuels, despite the fact CARB willingly uses models to assign carbon penalties (such as land use change) to biofuels,” Jennings writes. “To help breakthrough this stonewalling and convince market regulators and lifecycle modelers to provide carbon credits for certain farming practices, ACE is leading a pilot project in South Dakota funded by USDA’s Natural Resource Conservation Service Regional Conservation Partnership Program (RCPP). Our ultimate goal is to develop a non-proprietary tool for farmers and ethanol plants to prove farm-level benefits in securing pathways to low carbon or clean fuel markets.”

ACE’s full comments can be accessed here.

Interview 4/5/22 on AgriTalk on need for EPA to update modeling available here.


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