The U.S. Department of Energy’s Bioenergy Technologies Office (BETO) on May 30 released an updated version of its 45ZCF-GREET modeling tool to account for new feedstocks and methods of production, including ethanol from corn wet-milling and natural gas from coal-mine methane. 

The GREET (greenhouse gases, regulated emissions and energy use in technologies) model was first developed by Argonne National Laboratory in 1994. The tool is designed to access the life cycle impacts of technologies, fuels, products and energy systems across various stages of the supply chain. The agency has since developed multiple GREET models designed for specific use cases. 

The DOE in January 2025 released the 45ZCF-GREET model, which is specifically designed to calculate lifecycle greenhouse gas (GHG) emissions for the 45Z clean fuel production tax credit. 

The agency has now updated the 45ZCF-GREET model, noting the changes “will allow a wider range of farmers and companies to do business in America’s thriving alternative fuels market.” 

Information released by the DOE outlines eight specific changes the agency has made to 45ZCF-GREET. The changes include: 

• Added pathway for ethanol from U.S. corn wet mills. A simplified plant-level allocation by mass is applied to derive the results for ethanol. The same indirect emissions value per MJ for dry mill corn ethanol is applied to wet mill ethanol.
• Revised Methanol input for biodiesel production to be entered in gallons as opposed to units of energy (MMBtu).
• Added coal as a process input option for biodiesel via Transesterification pathways.
• Clarifies in the GREET User Manual that Carbon capture utilization and sequestration (CCUS) allows CO₂ stored in U.S. Class II wells used for enhanced oil recovery (EOR), in addition to Class VI wells. (Note: No changes to model only revisions to user manual.)
• Corrected Summary Table 9b. in the GREET User Manual to reflect final Indirect land use change (ILUC) emissions factors for soy and canola. (Note: No changes to model or modeled results, only correcting summary data as presented in the manual.)
• Added pathway for alternative natural gas from coal mine methane (CMM) capture and upgrading.
• Lifecycle emissions results updated to include the output in kilograms of CO₂ equivalent per million British thermal units (kg CO₂e/MMBtu), consistent with Section 45Z tax credit.
• Added text to the GREET User Manual to quote Notice 2025-11, sec. 401 to clarify that these (and potential future) model updates, including new types, categories or pathways, may be used immediately.

“The Trump administration is committed to helping American fuel producers make the most of our country’s abundant biomass resources,” said Principal Deputy Assistant Secretary for Energy Efficiency and Renewable Energy Lou Hrkman. “The latest version of the 45ZCF-GREET model will allow more of our farmers to reap the benefits of a rapidly expanding market for alternative transportation fuels.” 

Growth Energy is welcoming the new guidance, noting it will create jobs and unleash new investments. “By lifting needless restrictions on wet mills and different end uses for captured carbon, the updated user manual ensures that more farmers and biofuel producers will have the freedom and flexibility to invest in U.S. energy dominance while supporting stronger markets for American agriculture,” said Emily Skor, CEO of Growth Energy. “In conjunction with an extension of the credit under consideration by lawmakers, this guidance will help restore market certainty and increase American competitiveness in the race for the next generation of liquid fuel solutions. We applaud Energy Secretary Wright for working with the U.S. Department of the Treasury to deliver a fairer, more accurate model for calculating incentives that will help drive American energy dominance and spur economic growth.”