Review of EPA Workshop on Biofuel Greenhouse Gas Modeling

EPA’s Biofuel Greenhouse Gas Modeling Workshop provided updates on ongoing research related to greenhouse gas (GHG) emissions associated with biofuels. Most of the material covered topics associated with land use conversion and the carbon stocks associated with
different land cover types. Many prominent researchers and models were represented at the conference. Representatives of certain other modeling techniques, such as the FAPRI/FASOM model used by EPA in 2010, were notably absent at the workshop. Commentary on the relevance of individual presentations is discussed in the subsequent sections, with a focus on providing EPA feedback on the questions on which it seeks comment regarding sources of data for modeling, best models to use, how to address uncertainty, and how to incorporate best available science.

In general, the presentations kept to the presenter’s area of research and did not provide a direct review of the GHG emissions of biofuels in relationship to the EPA’s 2010 regulatory impact analysis (RIA) (EPA, 2010) or revised 2022 draft RIA. While reviewing these areas of research in isolation is an interesting exercise that is helpful for furthering the science over the long term, for EPA to “incorporate the best available science into an update of our lifecycle analysis (LCA) of biofuels” EPA will need to consider how to bring these research areas together into a holistic analysis.

The workshop focused primarily on issues related to land use conversion (LUC). Other LCA topics relevant to the analysis of biofuels including reassessment of the 2005 petroleum baseline, petroleum production and its impact on biofuels, natural gas and electric power were not part of the workshop discussion.

The opinions in this report are based on attendance of the workshop as well as extensive prior work on the GHG emissions of biofuels, including a February 2022 Report on Review of GHG Emissions of Corn Ethanol under the EPA RFS2 submitted as comment to the 2020‐2022 RFS Annual Rule.