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RFA Supports EPA’s Proposed ‘Anti-Backsliding’ Determination, but Says Agency Used ‘Outdated and Unreliable’ Modeling

July 8, 2020

Environment, EPA, Regulatory, RFS


In comments submitted today to the Environmental Protection Agency, the Renewable Fuels Association expressed support for the Agency’s proposal to determine that no additional measures are necessary to mitigate “potential adverse air quality impacts” associated with the Renewable Fuel Standard. However, RFA’s comments also challenged the flawed air quality modeling and analysis conducted by EPA to inform the proposed determination.

“We agree that no additional ‘fuel control measures’ are necessary, but we reach this conclusion for a different reason than EPA,” wrote RFA President and CEO Geoff Cooper. “We believe no additional measures are necessary because the scientific evidence demonstrates that increasing the concentration of ethanol in gasoline generally improves air quality and does not cause ‘adverse air quality impacts.’”


Earlier this year, EPA completed an “anti-backsliding study” to determine whether the RFS would adversely impact air quality. After considering the results of the study, the Clean Air Act requires EPA to either promulgate new regulations to mitigate any adverse impacts on air quality or to determine that no such measures are necessary.

In May, EPA proposed that no additional mitigation measures are necessary to mitigate adverse air quality impacts. While RFA supports that determination, the anti-backsliding study conducted by EPA often misrepresents ethanol’s air quality impacts.


“We remain concerned that the Anti-Backsliding Study (ABS) used to inform the proposed determination continues to rely upon an outdated and unreliable emissions model, the Motor Vehicle Emission Simulator (MOVES), to estimate the emissions impacts of ethanol-blended motor fuels,” according to RFA’s comments. “The Agency, itself, has acknowledged the ABS ‘has a number of limitations.’ Indeed, it does. We firmly believe this model and the resulting ABS report are inappropriate tools for assessing the real-world air quality impacts of renewable fuels.  We have repeatedly asked the Agency to look at empirical data and real-world emissions measurements when assessing the air quality impacts of ethanol-blended gasoline, and we renew that request today.”


According to multiple independent third-party reviews, the MOVES2014 model used by EPA to estimate the exhaust emissions of ethanol-gasoline blends is fatally flawed due to its use of manipulated input data and unreliable “adjustment factors” and equations. RFA’s comments recommend several options for improving EPA’s evaluation of emissions related to ethanol-blended fuels and the association offers to “…work constructively with the Agency to complete a more meaningful assessment of ethanol’s air quality impacts.”


Finally, RFA’s comments note that real-world data collected by EPA show significant reductions in air pollution during the period of RFS implementation. “Since the RFS was adopted in 2005, EPA data from air monitors show that carbon monoxide concentrations are down 31%, nitrogen dioxide is down 22%, ozone is down 13%, fine particulate matter is down 37%, and sulfur dioxide is down 81%,” according to the comments. “The levels of all these pollutants have now fallen below the national standard. The emissions trends strongly suggest that increased use of ethanol (which led to a simultaneous reduction in the use of aromatics and olefins) has played an important role in reducing air pollution.”



Ken Colombini