CI Score (Carbon Intensity)

A carbon intensity (CI) score is the lifecycle greenhouse-gas emissions of a transportation fuel, expressed in grams of carbon- dioxide-equivalent per megajoule of fuel energy delivered (gCO2e/MJ). CI is the regulatory metric used in California's Low Carbon Fuel Standard, Oregon's Clean Fuels Program, Washington's Clean Fuel Standard, and the U.S. federal Section 45Z Clean Fuel Production Credit. A lower CI score indicates a fuel with smaller lifecycle emissions per energy unit.

What lifecycle includes

A CI score is a "well-to-wheels" lifecycle accounting that includes:

• Feedstock production (e.g., agriculture for soybean oil, crude extraction for petroleum)
• Feedstock transport to the processing facility
• Conversion process (e.g., transesterification for biodiesel, hydro- treating for renewable diesel)
• Distribution and storage
• End-use combustion (the tailpipe CO2 emissions)
• Where applicable, indirect land-use change (ILUC) emissions for crop-based feedstocks

For petroleum gasoline and diesel, the CI score reflects the average lifecycle of the U.S. petroleum supply, with regional adjustments in some programs.

Calculation methodology

The CI score is calculated using a sanctioned version of the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model maintained by Argonne National Laboratory. California's LCFS uses CA-GREET 3.0, a state-modified version with California-specific electricity grid mix and feedstock parameters. Oregon's CFP and Washington's CFS use OR-GREET and WA-GREET respectively. Federal Section 45Z uses a Treasury-approved version of GREET fixed by IRS notice for each compliance year.

Pathway certification

For program use, a CI score must be certified through a regulator- approved pathway petition. CARB's pathway process is at 17 CCR 95488; Oregon's at OAR 340-253; Washington's at WAC 173-424. Treasury's process for Section 45Z is set out in IRS Notice 2025-10 and the related proposed regulations.

Tiered pathway approaches

CARB's framework offers two pathway tiers:

• Tier 1 — simplified calculator for established pathways (e.g., conventional soybean-oil biodiesel, conventional corn-starch ethanol). Regulator-published default factors; minimal site-specific documentation.
• Tier 2 — detailed pathway for novel fuels or facility-specific operations. Site-specific operating data, monitoring plan, and third-party verification required.

Most large biofuel facilities operate Tier 2 pathways because the site-specific operating data typically yields a lower CI than the Tier 1 default.

Indirect land-use change

ILUC is the marginal carbon emission attributed to crop-based fuels when expanded biofuel production drives expansion of cropland into non-crop land cover. Each program adopts a different ILUC factor for each feedstock; CARB's CA-GREET 3.0 uses 19.4 gCO2e/MJ for soy biodiesel, 19.8 for canola biodiesel, 7.6 for corn ethanol, and so forth. ILUC is the most contested element of CI calculation and the subject of substantial peer-reviewed literature.

Historical CI values

Public CARB pathway records show the following representative certified CI ranges (in gCO2e/MJ): conventional soybean-oil biodiesel ~50, used-cooking-oil biodiesel ~15–25, conventional corn-starch ethanol ~60–70, sugarcane ethanol ~40, renewable diesel from used cooking oil ~20, electric vehicle (CARB grid mix) ~40 well-to-wheels. These values shift over time as CARB updates its grid mix and modeling.

CI score in revenue stacking

A single gallon of low-CI biofuel sold into California can generate revenue from multiple stacked instruments tied to its CI score:

• A federal D4 RIN under the RFS (worth one or more RINs depending on the EV multiplier in 40 CFR 80.1415)
• An LCFS credit, valued in MTCO2e and converted to a per-gallon contribution at the prevailing LCFS credit price
• A federal Section 45Z producer-side credit, valued at up to $1.00 per gallon for non-SAF or $1.75 for SAF, scaled by the gallon's CI delta below the program baseline
• A state-level credit in Oregon CFP, Washington CFS, or BC LCFS for gallons supplied into those jurisdictions

The CI score is the common input across all of these stacked instruments — it determines the LCFS credit yield, the 45Z credit value, and (through the EV multiplier framework) the federal RIN yield. This is why CI score certification is operationally central to modern biofuel producer economics.

Sources

CARB regulations: 17 CCR 95488 (pathway certification), 17 CCR 95485 (CI-to-MTCO2e conversions). Oregon: OAR 340-253. Washington: WAC 173-424. Federal Section 45Z: IRS Notice 2025-10. Modeling: GREET, Argonne National Laboratory; CA-GREET 3.0, CARB.