Summary of September 2026 US IRS 45Z-GREET Model Updates

On September 8, 2026, the United States Department of Energy (DoE) issued a surprise update to the 45ZCF-GREET model along with revised instructions, and recommendations regarding the 45Z Provisional Emissions Rate (PER) process. 

The updated model and instructions provide tabs and an associated emissions rate table that now include wastewater sludge, landfill gas, food scrapes, corn stover, grain stillage, fats oils and greases (FOG) and septage, DCO, DSO, and mixed high moisture organic wastes, in addition of dairy and swine manure, as listed feedstocks for renewable natural gas (RNG).  The new version of the 45ZCF-GREET model also allows for the emissions rate (ER), equivalent to carbon intensity (CI), calculation of Canadian and Mexican used cooking oil (UCO) and further separates USMCA and international feedstocks.  It also allows for separated calculation of ERs for fuels produced before and after the implementation of the One Big Beautiful Bill Act (OBBBA) changes on January 1, 2026.  In another significant change, this new model allows for ER calculation, and associated crediting, for non-USMCA imported UCO produced during tax year 2025.  As a result, the September 2026 45ZCF-GREET model is valid for EF calculation for fuels produced since the start date of the program on January 1, 2025.

Even though they are still not included in the emissions rate table, producers of fuels derived from poultry and beef manure are encouraged to postpone submitting a PER petition as DoE has stated that these will be added in a future update to the 45ZCF-GREET model, expected in November 2026.  To learn more about the PER process, read our blog post here.

The new September 2026 45ZCF-GREET model also allows users to include climate smart ag emissions reduction modeled in USDA Feedstock Carbon Intensity Calculator (FD-CIC), which was published in June 2026.

If you are a fuels producer who needs support with the 45ZCF-GREET model or calculating your facility’s emissions factor under 45Z, TRICORD’s lifecycle assessment experts are here to help.  For inquiries, please contact our low carbon fuels team lead, Hannah Losey P.E., at Hannah.Losey@tricordconsulting.com.