45Z (Clean Fuel Production Credit)

The Section 45Z Clean Fuel Production Credit is the U.S. federal producer-side income tax credit at 26 USC § 45Z that took effect 1 January 2025 and runs through 31 December 2029 under the One Big Beautiful Bill Act of 2025 (OBBBA), which extended the original 31 December 2027 sunset. 45Z replaced the biodiesel blender's tax credit (BTC) and several other clean-fuel incentives that expired on 31 December 2024.

Statutory framework

26 USC § 45Z was enacted as part of the Inflation Reduction Act of 2022 (Public Law 117-169) and codified the framework for a carbon-intensity-indexed federal credit on transportation fuel produced and sold in the United States. The base credit value is set by formula and varies with the fuel's lifecycle carbon intensity (CI) relative to the program's baseline. Under the statute the credit floor is $0 — fuels with CI above the baseline receive no credit.

Carbon-intensity calibration

45Z is the first U.S. federal fuel credit that varies with lifecycle greenhouse-gas emissions. The credit per gallon is determined by the fuel's CI score, which is calculated using a Treasury-approved version of the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model maintained by Argonne National Laboratory. The specific GREET version and emission factor settings are fixed by Treasury notice for each compliance year. Producers must obtain a provisional or final pathway determination from Treasury before they can claim the credit.

SAF bonus

Sustainable aviation fuel (SAF) is treated separately under § 45Z. The maximum credit value for SAF is $1.75 per gallon at the lowest CI score, compared with $1.00 per gallon for non-SAF transportation fuel. This differential is intended to direct incentives toward aviation decarbonization, where alternative fuels remain the principal near-term abatement pathway.

Wage-and-apprenticeship requirements

To claim the maximum credit value, a producer must meet prevailing- wage and apprenticeship requirements set out in section 45(b) of the Internal Revenue Code. Producers that do not meet these requirements receive a fraction (one-fifth) of the maximum credit. The wage-and-apprenticeship structure is consistent across the IRA's energy tax credits enacted in 2022.

OBBBA extension

The original 45Z sunset was 31 December 2027. The One Big Beautiful Bill Act of 2025 extended the program through 31 December 2029 and introduced several refinements to the credit calculation, including adjustments to the SAF bonus and clarifications on the indirect-land-use-change (ILUC) component of the CI score. The extension was enacted in July 2025.

Effect on biodiesel/renewable diesel value chain

The transition from BTC (blender-side, fuel-agnostic $1.00/gallon) to 45Z (producer-side, CI-indexed up to $1.00/gallon for non-SAF and $1.75 for SAF) shifted the federal incentive framework from a flat volume payment to a CI-weighted production payment. Public commentary in the Federal Register and trade-association filings has documented the operational impact on biodiesel and renewable diesel producers: feedstock-mix decisions, facility-level GREET pathway documentation, and the prevailing-wage compliance setup are now part of the producer's standard operating cost.

Procedural posture

Treasury and the IRS continue to publish implementing guidance. The Notice 2025-10 series and the proposed regulations issued in early 2025 govern the pathway determination process, the documentation requirements, and the CI-score calculation methodology. Producers typically engage a registered emissions-modeling consultant to prepare the pathway petition and the supporting feedstock-tracing records.

Sources

Statute: 26 USC § 45Z (Clean Fuel Production Credit), 26 USC § 45(b) (wage and apprenticeship requirements). Enabling legislation: Inflation Reduction Act of 2022 (Public Law 117-169); One Big Beautiful Bill Act of 2025 (extension to 31 December 2029). Treasury guidance: IRS Notice 2025-10 series and the 45Z proposed regulations (2025). Greenhouse-gas modeling: GREET, Argonne National Laboratory.