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U.S. Department of Energy Releases 45ZCF-GREET Model

On January 15, 2025, the U.S. Department of Energy released the 45ZCF-GREET model. This announcement follows the U.S. Department of the Treasury and Internal Revenue Service guidance on the Clean Fuels Production Credit (section 45Z) released on Jan. 10, 2025.

The Clean Fuels Production Credit was created under the Inflation Reduction Act and provides a tax credit for the production of transportation fuels with life cycle greenhouse gas (GHG) emissions below certain levels. The credit applies to eligible transportation fuel produced domestically after Dec. 31, 2024, that is sold by Dec. 31, 2027.

45ZCF-GREET includes feedstock-specific fuel production pathways for sustainable aviation fuels (SAF) and non-SAF fuels. The model is designed specifically to evaluate life cycle GHG emissions to meet the requirements of section 45Z and to include features that make it easy to use for taxpayers.

GREET is a tool that assesses a range of life cycle energy, emissions, and environmental impact challenges and that can be used to guide decision making, R&D, and regulations related to transportation and the energy sector.

For any given energy and vehicle system, GREET can calculate:

Total energy consumption (nonrenewable and renewable)
Fossil fuel energy use (e.g., petroleum, natural gas, coal)
Greenhouse gas emissions
Air pollutant emissions
Water consumption.

GREET models are developed for specific use cases. Users are responsible for ensuring they have selected the correct model for their intended purpose. For instance, annual releases of R&D GREET are comprehensive in order to inform the life cycle assessment technical community and elicit stakeholder feedback. R&D GREET may not be the version of GREET adopted in independent regulatory programs (e.g., tax credits). Stakeholders seeking a GREET model for purposes of compliance with a given regulatory program should review guidance specific to that program to ascertain the appropriate version of GREET to use.

DOE also released the 45ZCF-GREET User Manual which describes how the 45ZCF-GREET model characterizes life cycle GHG emissions of transportation fuel production pathways and provides guidance for using the model to determine emissions rates for clean fuels under section 45Z.

The 45ZCF-GREET model and user manual are available on the DOE GREET webpage at https://www.energy.gov/eere/greet.