Ecology is considering amendments to Chapter 173-424 WAC, Clean Fuels Program Rule. The rule aims to reduce the life-cycle greenhouse gas emissions per unit energy, or carbon intensity (CI), of transportation fuels used in Washington. This rulemaking is to align the Clean Fuel Standard (CFS) with Engrossed Substitute Senate Bill 5447 (ESSB 5447), which was signed into law on May 3, 2023. The law promotes the production and use of low-carbon alternative jet fuels, which are more commonly referred to as sustainable aviation fuels (SAF), in Washington. Ecology’s rulemaking will comply with ESSB 5447 by updating the date at which SAF pathway applications can be submitted for CFS credit generation. SAF reduces emissions from aviation, which has been identified as one of the most difficult transportation sectors to decarbonize. Lowering aviation emissions will also improve air quality and reduce health burdens on people living near airports and airport workers. Additionally, the rulemaking may consider the following changes to strengthen/streamline the CFS program: • Establishing requirements for a third-party verification program for fuel pathways and data reports submitted by program participants. • Establishing standards to encourage the production of low carbon intensity sustainable aviation fuels (SAF) production. • Amending/refining the compliance and enforcement process for the CFS program. • Updating the rule language to improve clarity and readability, align the rule with guidance documents, correct errors, and make miscellaneous improvements to program implementation. • Updating book-and-claim accounting requirements for electricity and biomethane. • Harmonizing the rule with Oregon and/or California low carbon or clean fuel program requirements. Ecology is not considering amending the other main components of the program, including annual carbon intensity standards, the Tier 2 WA-GREET model, and land use change factors.