Fuel pathways and carbon intensity

Each fuel reported in the Clean Fuel Standard is assigned a carbon intensity score based on its fuel pathway. A fuel pathway accounts for the greenhouse gas emissions produced throughout a fuel’s life cycle — from production to distribution and use. This is sometimes referred to as a “well-to-wheels” or “life cycle” analysis, too.

Fuel producers must apply for a certified carbon intensity score to find out how many credits or deficits their fuel generates in the program.

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Washington offers three ways to determine a fuel’s carbon intensity score:

Re-certifying an approved value from California or Oregon
Applying for a new value using state-approved models
Using temporary values while awaiting certification

To apply for a certified carbon intensity score, please submit an application through the Alternative Fuel Portal (AFP). For step-by-step instructions, check out the Washington Fuels Reporting System (WFRS) User Guide and Alternative Fuel Portal (AFP) User Guide.

Like all other CFS participants, fuel pathway holders must also pay an annual participation fee. For more compliance information, visit our Requirements webpage.

WA-GREET: Determining the carbon intensity of fuels

Ecology determines the carbon intensity of fuels on a life cycle basis using the Washington “Greenhouse gases, Regulated Emissions, and Energy use in Technologies” model, or WA-GREET. Argonne National Laboratory developed the GREET model, which we have adapted for our regulatory policies.

Download the WA-GREET Excel file.

The spreadsheet file is large. Please be patient during the download.
At the password prompt, click “Read Only” to proceed.
Allow additional time for the file to fully load after selecting “Read Only.”

Other calculators, models, and references

WA Crude Carbon Intensity Analysis
WA Utility Carbon Intensity Calculator
WA-GREET Electric Power document
Other GREET models:
- Montana fuels
- Utah fuels
WA-GREET supplemental document
WA Blended Fuel Carbon Intensity Calculator:
- 2017 Baseline Carbon Intensities for Blended Fuels
- Carbon Intensities of Blended Fuels for Substitute Pathways

Fuel producers can determine their carbon intensity score in three different ways. Follow these steps to apply for a carbon intensity value:

If your fuel already has a carbon intensity value approved by the California Air Resources Board or the Oregon Department of Environmental Quality, you can:
- Apply to Ecology to re-certify that value, using WA-GREET 3.0, with adjustments for transportation mode and distance to its destination in Washington.
- Submit the same application packet and approval documents you sent to California or Oregon.
- Submit your fuel pathway application through the Alternative Fuel Portal.
If your fuel doesn’t have a carbon intensity value from California or Oregon, you can:
- Apply to us for certification.
- Use our simplified calculators for common fuel types or the WA-GREET model for more complex fuel pathways.
- Submit your fuel pathway application through the Alternative Fuel Portal.
If your fuel pathway application has not been certified yet, you can use temporary carbon intensity values.
- Refer to page 33 of the Alternative Fuel Portal (AFP) User Guide and Table 8 in WAC 173‑424‑900 for more details.

The Clean Fuel Standard rule requires each electric utility in Washington to have a unique carbon intensity score for the electricity it generates.

Ecology sets these scores each year in coordination with the Washington State Department of Commerce’s Fuel Mix Disclosure report.

You can find the scores under the Electric Utility-Specific Carbon Intensity section of the Clean Fuel Standard Program Documents library.

The Clean Fuel Standard rule (WAC 173-424-630) requires each electric utility in Washington to have a unique carbon intensity score. Ecology sets these scores annually with the Department of Commerce’s Fuel Mix Disclosure report.

The tabs below provide related resources and tools.

Tier 1 fuel pathways are intended for fuels with well-documented emissions factors.

Approved Tier 1 fuel pathways can be found in our Clean Fuel Standard Program Documents library under the Fuel Pathways section.

The list of approved pathways is updated regularly as pathways expire or are approved.

You can search for specific pathways or sort by feedstock, fuel type, or facility name.

Tier 1 calculators are used for fuels with well-documented emission factors. Learn how to calculate emissions for Tier 1 fuel pathways with step-by-step guidance in the Tier 1 Calculator Manual.

If a file opens with a password request, choose “Read Only” to open the document, download a copy to your device, and edit it from there.

Downloadable calculators

Biomethane production by feedstock

Other calculators

Alternative fuels

Renewable diesel: For renewable diesel production, made from used cooking oil, animal tallow, or vegetable oils.

Ethanol by feedstock

Starch and fiber ethanol: For ethanol production from starch and fiber sources.
Sugarcane-derived ethanol: For ethanol made from sugarcane.

Natural gas

Liquid natural gas and liquid to compressed natural gas: For the transition of natural gas to liquid form and its conversion to compressed natural gas.

Tier 2 fuel pathways focus on new and emerging fuels with a more complex life-cycle analysis than Tier 1 pathways.

Ecology started accepting new Tier 2 fuel pathway applications Oct. 1, 2024. Before this, we accepted only Tier 2 pathways certified by California or Oregon.

A list of current Tier 2 pathways can be found on our Clean Fuel Standard Program Documents library under the "Fuel Pathways" section. You can search for specific pathways or sort by feedstock, fuel type, or facility name.

To submit a Tier 2 fuel pathway application, use the step-by-step instructions in the Alternative Fuel Portal (AFP) User Guide using the WA-GREET model (linked above). Ecology reviews each application. Once we finish our review, a 45-day public comment period may follow.

Applications already approved by California or Oregon or those using standardized lookup values may not require a public comment period.

You can find pending and approved applications in the content below.

Please email WFRSAdmin@ecy.wa.gov with questions.

Fuel pathway applications and comment periods

Tier 2 fuel pathway applications

We invite the public, local governments, Tribes, and any others to review and comment on an application for a new Tier 2 fuel pathway and carbon intensity value under the Clean Fuel Standard.

We may approve a Tier 2 pathway for a fuel or feedstock fuel combination per WAC 173-424-610(5).

Public comments on proposed new Tier 2 fuel pathways will be accepted for 45 days prior to certification. If we receive relevant comments that suggest significant revisions of the originally published fuel pathway, an updated fuel pathway will be posted for an additional public comment period.

Once certified, this new fuel pathway can be reported in WFRS-CBTS for that quarter.

Posted date	Fuel pathway description	Comment period deadline	Received comments	Decision

Temporary fuel pathway applications

We invite the public, local governments, Tribes, and any others to review and comment on an application for new temporary fuel pathways — temporary pathways not already in the Clean Fuel Standard rule — and carbon intensity values under the Clean Fuel Standard. We may approve a temporary pathway for a fuel or feedstock fuel combination not found in Table 8 of WAC 173-424-900 per WAC 173-424-610(11).

Public comments on proposed temporary fuel pathways will be accepted for 45 days prior to certification. If we receive relevant comments that suggest significant revisions of the originally published fuel pathway, an updated fuel pathway will be posted for an additional public comment period.

Once certified, this fuel pathway can be reported in WFRS-CBTS for the quarter in which it was approved.

Posted date	Temporary fuel pathway description	Applications materials	Comment period deadline	Received comments	Decision
Nov. 2, 2023	Establishing temporary fuel pathways codes and carbon intensity values for renewable naphtha and renewable gasoline blend stock.	Letter to Ecology Proposed temporary fuel pathway	Dec. 17, 2023	1. Phillips 66	Temporary pathways - approved

Substitute fuel pathway applications

We invite the public and local governments, Tribes, and any others, to review and comment on an application for new substitute fuel pathway and carbon intensity value under the Clean Fuel Standard.

Public comments on proposed new temporary fuel pathway will be accepted for 14 days prior to certification. If we receive relevant comments that suggest significant revisions of the originally published fuel pathway, an updated fuel pathway will be posted for an additional public comment period.