EPA released its Anti-backsliding Study for Renewable Fuels in May 2020. Along with the study, EPA released other supporting materials, including a Proposed Determination document. Upon performing an air quality analysis of the impact of the increase in renewable fuels associated with the RFS, and comparing these emission and air quality changes to the effects of the on-road Tier 3 final rule, EPA concluded that fuel regulations to mitigate any emission increases as a result of the Renewable Fuel Standard (RFS) are not necessary.
We agree with EPA that fuel regulations to mitigate such impacts are not necessary. In fact, due to various methodological issues with the fuel properties EPA used, the study overstates any potential negative air quality effects of the RFS. Specifically, the study overstates ozone and PM impacts, and undercounts the reductions of toxics. When using appropriate fuel properties, hydrocarbon and NOx increases are significantly smaller (leading to lower ozone impacts), PM emissions decline instead of increasing (leading to possible PM air quality benefit for the RFS), and toxics benefits of the RFS are higher.
This document is a review of EPA’s emission inventory and air quality analysis performed for the Anti-backsliding Study, which appropriately focused on vehicle emissions pursuant to the Clean Air Act’s statutory mandate in section 211(v).
EPA’s proposed determination is that it is not necessary to promulgate fuel regulations to mitigate the air quality impacts resulting from required renewable fuels volumes. Although EPA’s analysis amply supports this proposed determination, improving the analysis with ethanol fuel effects data and improved MOVES correction factors would show that the modest adverse impacts EPA observed are lessened or entirely absent. An improved analysis based on real fuel data would show ethanol-blended fuels are associated with PM improvements, lower benzene and 1,3 butadiene, and lower carbon monoxide emissions.