2026 tax preference review: Biogas Equipment Used in Landfills
July 2026
Aline Meysonnat, research analyst
Pete van Moorsel, tax review coordinator; Eric Thomas, legislative auditor
Contact information
Legislative auditor's conclusion
Five landfills process landfill biogas into renewable natural gas or electricity, achieving the Legislature's goal.
Read the full reportKey points
- As organic waste decays in landfills, it creates biogas, which contains methane. Landfills are required to collect and control biogas.
- Landfills do not pay sales and use tax for equipment used to process biogas into renewable natural gas or electricity.
- The Legislature intended the preference to increase the production of renewable natural gas in Washington.
- Two of the five landfills that process biogas started this work after the preference took effect, meeting the Legislature's goal.
- Current reporting requirements produce limited data about use and savings. This likely understates preference use.
- Joint Legislative Audit and Review Committee (JLARC) staff estimate that beneficiaries could save $428,000 per year in tax related to maintenance and repair.
Legislative auditor’s recommendations
State law requires the legislative auditor to recommend legislative action for each tax preference.
The legislative auditor makes two recommendations.
Recommendation #1
The Legislature should continue the preference beyond its January 2029 expiration because it meets the Legislature's goal.
Two landfills started processing biogas after the preference passed. Today, five landfills perform such work.
If this preference were continued without change, beneficiaries would have future tax savings like those shown in the savings summary graph. This would reduce state revenues by a corresponding amount.
On or before the preference's expiration date of January 1, 2029.
Responses from the Office of Financial Management (OFM) and the Department of Revenue (DOR) will be included with the proposed final report
Recommendation #2
The Legislature should modify the preference to require beneficiaries to provide more detailed reporting about the use of the preference and production of renewable natural gas.
Beneficiaries could report the amount of tax savings per year and the amount of landfill biogas processed in an annual tax performance report.
This would facilitate future reviews of the tax preference.
None
At the discretion of the Legislature.
Responses from the Office of Financial Management (OFM) and the Department of Revenue (DOR) will be included with the proposed final report.
Video summary
Read the full report
Biogas Equipment Used in Landfills (HTML)
Read an overview
Read the agency response
To be included in proposed final report
Legislative mandate