A group of nine senators sent a letter to U.S. EPA Administrator Michael Regan on April 1 urging the agency to improve its greenhouse gas (GHG) modeling for biofuels by adopting the Argonne National Laboratory’s GREET model.

The letter is related to a virtual public workshop hosted by the EPA on Feb. 28-March 1 that focused on GHG modeling for biofuels. The EPA used the workshop and an associated public comment period 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 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 public comment period was open through April 1.

“Adopting the GREET model will not only permit the federal government to further standardize its comparison of GHG emissions for biofuels like ethanol, biodiesel, and sustainable aviation fuel, but enable over 50,000 registered GREET users to more readily compared renewable fuels to other sources of energy,” the senators wrote.

The senators stress that use of the GREET model would permit consistent comparisons between petroleum-based fuels, natural gas systems, electric generation, and renewable fuels derived from a variety of technology pathways, accounting for the lifecycle carbon intensity of key farming inputs. “We ask that EPA utilize the GREET model as the baseline GHG determination for biofuels so that stakeholders may have the opportunity to readily compare the GHG intensity of competing energy sources and policymakers may have a fuller picture of how to decarbonize the energy and transportation sectors,” the senators wrote.

The letter is signed by Sens. John Thune, R-S.D.; Amy Klobuchar, D-Minn.; Chuck Grassley, R-Iowa; Dick Durbin, D-Ill.; M. Michael Rounds, R-S.D.; Sherrod Brown, D-Ohio; Joni Ernst, R-Iowa; Tammy Duckworth, D-Ill.; and Roger Marshall, R-Kan.

A full copy of the letter can be downloaded from Grassley’s website.