The US Department of Energy (DOE) has released an update of its 45ZCF-GREET model, which is used to calculate fuel emission rates for the 45Z clean fuel production credit, Ethanol Producer Magazine wrote.
Published on 12 June, the update provided much-needed certainty for the US renewable fuel industry, the report on the same date said.
Commenting on the publication of the update, Kurt Kovarik, Clean Fuels Alliance America’s vice president of Federal Affairs, said: “Biodiesel, renewable diesel and sustainable aviation fuel (SAF) producers are grateful that Congress adopted beneficial changes to the 45Z credit last July through the One Big Beautiful Bill. They now have certainty that those changes can be claimed for their current tax year.”
First launched more than three decades ago, the DoE’s GREET (greenhouse gases, regulated emission and energy use in technologies) tool can calculate energy consumption, fossil fuel use, greenhouse gas emissions, air pollutant emissions and water consumption for a variety of transportation fuels on a well-to-wheels basis.
In early 2025, the DOE launched a 45Z-specific version of GREET (45ZCF-GREET), which was designed to aid biofuel producers in calculating the value of their 45Z tax credits. Initial revisions to 45ZCF-GREET were made in May 2025.
The latest version of the model included additional revisions, including updates to bring it in line with changes included in the One Big Beautiful Bill Act (OBBBA), which was signed into law by US President Donald Trump in July 2025.
In line with OBBBA, the updated version of 45ZCF-GREET eliminated indirect line use change (iLUC) from the model’s carbon intensity (CI) calculations.
The model also implemented changes to 45Z that prevented feedstocks sourced from outside the USA, Mexico and Canada from qualifying for 45Z fuel production.
For all fuel pathways, the model had been updated to use the most recently available data, Ethanol Producer Magazine wrote.
In addition, results for all pathways were given for fuels produced in 2025 and fuels produced after 31 December 2025, to reflect OBBBA policy changes.
