The U.S. Department of Energy’s Bioenergy Technologies Office recently released an updated version of its 45ZCF-GREET — greenhouse gases, regulated emissions and energy use in technologies — modeling tool to account for new feedstocks and methods of production, including ethanol from corn wet-milling and natural gas from coal-mine methane.

First developed in 1994, the tool is designed to assess the life cycle impacts of technologies, fuels, products and energy systems across various stages of the supply chain. The version released in January 2025 is specifically designed to calculate lifecycle greenhouse gas emissions for the 45Z clean fuel production tax credit. Multiple GREET models have been developed for specific use cases, and the new changes “will allow a wider range of farmers and companies to do business in America’s thriving alternative fuels market,” according to the agency.

The model now includes a pathway for alternative natural gas from coal mine methane capture and upgrading, coal as a process input option for biodiesel via transesterification route and a simplified pathway for ethanol from corn wet mills. Lifecycle emissions results have been updated to include the output in kilograms of carbon dioxide equivalent per million British thermal units, consistent with Section 45Z tax credit.