DOE updates 45Z CF-GREET model, biofuel industry welcomes credit tool

The U.S. Department of Energy’s June 12 update to the 45ZCF-GREET model should improve carbon scores for domestic ethanol, biodiesel, renewable diesel and SAF projects that can document lower-emission power and carbon capture, while tightening the rules around feedstocks and negative carbon intensity claims after Dec. 31, 2025. The revision matters because 45Z is the accounting tool behind the Clean Fuel Production Credit, which applies to eligible transportation fuel produced domestically after Dec. 31, 2024, and sold by Dec. 31, 2027.

The new model uses R&D GREET 2025 Rev. 1 data and assumptions and makes several technical changes that will flow through plant-level CI scores. DOE split behind-the-meter electricity into “Onsite Behind-the-meter Electricity: Integrated” and “Onsite Behind-the-meter Electricity: EAC,” changed modeled hydrogen inputs from 45V to 45Z inputs, and added a Hydrogen Production pathway requirement before hydrogen can be counted as a process fuel in other pathways. It also split “Pipeline CMM” into “45Z Modeled CMM” and “45Z Modeled CMM CI,” lowered the flaring-efficiency assumption in background counterfactual calculations to 98% from 99.85%, added CCS parameters and multiple CMM upgrading technology options, and added new corn stover inputs for renewable diesel and SAF via gasification and FT.

For ethanol, the update is most important for producers that can show tighter feedstock and energy accounting, especially plants positioned for exports. Growth Energy CEO Emily Skor said the update “builds on the progress made by Congress and President Trump in the One Big Beautiful Bill Act” and “reaffirms the removal of flawed indirect land-use change penalties on American biofuels and support[s] the eligibility of undenatured fuel ethanol for American exports.” DOE also renamed “Corn Hydrozylate Production” to “Hydrolyzed Corn Protein” and added two selectable pretreatment methods for ethanol from corn stover via fermentation.

The late-2025 policy changes in the user manual are likely to be the sharpest dividing line for project economics. For fuels produced after Dec. 31, 2025, DOE deducts indirect land-use change contributions, bars feedstocks sourced outside the United States, Mexico and Canada, and restricts some negative CI values. That puts pressure on import-dependent renewable diesel and SAF pathways, while favoring domestic crop, waste and captured-methane chains that can prove stronger emissions performance.

Industry groups welcomed the change. Renewable Fuels Association CEO Geoff Cooper said the group was grateful for the updated model and will be engaging members across the supply chain on the implications. Clean Fuels Alliance America Senior Vice President Kurt Kovarik said the update provides certainty for biofuel producers, growth for the biofuels industry and new markets for U.S. farmers.

The DOE release follows the agency’s first 45ZCF-GREET model in January 2025 and earlier Treasury and IRS guidance on the credit. USDA’s farming-practices calculator remains in interagency review, and Treasury still has to finalize how producers claim the credit, leaving the model as a major step, but not the final piece, of 45Z implementation.