DOE 45Z GREET model, shifting economics for clean fuels

The U.S. Department of Energy on June 12 released an updated 45ZCF-GREET model that gives ethanol, biodiesel, renewable diesel and SAF producers a fresh way to calculate lifecycle greenhouse-gas intensity under the Clean Fuel Production Credit. The update matters because 45Z now sits near the center of clean-fuels economics, and even small changes in carbon intensity can shift credit value, project returns and feedstock strategy.

Why the update matters now

The new model gives tax, finance and compliance teams a current reference point for current-year claims instead of forcing them to rely on an old draft or extrapolated assumptions. DOE’s model now includes calculations for fuels produced in both 2025 and 2026, which is especially useful for plants and developers that need to decide whether a pathway qualifies, how much credit it can earn and whether a carbon-cutting investment clears the hurdle.

That is where the money is for ethanol plants considering carbon capture, low-carbon power and other emissions-reduction projects. It also affects biodiesel, renewable diesel and SAF developers weighing feedstock contracts, project financing and offtake terms, because a few points of lifecycle carbon can reshape a project’s economics.

What changed in the DOE model

DOE’s original 45ZCF-GREET model was released on January 15, 2025, after Treasury and IRS guidance on January 10, 2025. That first version was built specifically to evaluate lifecycle emissions for section 45Z and included feedstock-specific pathways for SAF and non-SAF fuels. The original framework covered eligible transportation fuel produced domestically after December 31, 2024 and sold by December 31, 2027.

The June 12 update folds in improved carbon-scoring data from the R&D GREET model, including updated assumptions for inputs such as natural gas. It also reflects later statutory changes that extended and revised 45Z, so the model is no longer just a planning tool for a narrow start-up window. For the market, the practical effect is simple: a cleaner carbon score can raise the credit value a pathway captures, while a worse score can push a project out of the money.

How the economics shift across fuels

For ethanol, the update is a direct boost because Growth Energy said the model reaffirms removal of indirect land-use change penalties on American biofuels and supports eligibility of undenatured fuel ethanol for American exports. That matters for producers that have been punished by carbon assumptions they viewed as disconnected from the actual plant-level emissions profile.

Clean Fuels Alliance America said biodiesel, renewable diesel and SAF producers now have certainty that Congress’s changes can be claimed in their current tax year, which for some ends as early as this summer. That certainty matters as much as the score itself, because lenders and equity partners want to know whether a project can actually monetize 45Z inside the right tax year before committing capital.

For renewable diesel and SAF, the updated model is less about a single policy win and more about timing and bankability. Producers can now model the updated rules against feedstock supply, low-carbon hydrogen, power sourcing and carbon capture decisions with a common DOE framework in hand.

The policy changes baked into the model

KPMG said the revised model and user manual reflect changes from the One Big Beautiful Bill Act for fuels produced after December 31, 2025. Those changes include removal of ILUC contributions, ineligibility for feedstocks sourced outside the United States, Mexico and Canada, restrictions on negative values for some fuels and limits on certain renewable natural gas pathways.

KPMG also said section 45Z was amended and extended by two years under the law, making it available for fuels produced after December 31, 2024 and sold before December 31, 2029. That longer runway gives developers more room to line up projects, but it also makes the DOE model more important, since the credit now covers a broader set of production years and compliance scenarios.

Industry reaction points to real near-term value

Growth Energy chief executive Emily Skor welcomed the DOE update as a signal that the market is moving away from penalizing domestic ethanol with assumptions that do not belong in the credit calculation. The group’s reaction centered on two points: ILUC is gone, and exports of undenatured fuel ethanol are supported under the updated framework.

Clean Fuels Alliance America said the release gives producers current-year credit-calculation certainty after months of waiting for an up-to-date version. The group added that its vice president of federal affairs, Kurt Kovarik, testified at the IRS public hearing on May 28, 2026, after the group pressed Treasury in April comments and in a January letter to President Trump.

DTN reported that the Iowa Renewable Fuels Association said the update is the first time producers can input data and get results that reflect Congress’s changes, including removal of ILUC penalties. IRFA Executive Director Monte Shaw called the move away from "flawed, unscientific assumptions" a better recognition of biofuels’ carbon benefits.

What to watch next

The updated model does not end the fight over 45Z, but it gives the market a common scorecard. Producers, lenders and traders now have a DOE-backed tool to test whether carbon capture, feedstock shifts, power procurement or sourcing changes improve economics enough to move a project forward.

For ethanol, the near-term lift is the cleanest. For biodiesel, renewable diesel and SAF, the key question is how quickly projects can translate the new model into financeable assumptions. In a market where carbon intensity can swing credit value and capital access at the same time, DOE’s June 12 release is likely to set the terms of the next round of project economics.