Description
Emissions from the decay of materials disposed of at King County’s Cedar Hills Regional Landfill are the single greatest operational point source of GHG emissions from King County government. Emissions from closed landfills are much smaller but still significant. King County’s SWD will continue its comprehensive work to minimize LFG emissions at landfills; use captured LFG as a renewable energy source; improve landfill GHG emissions estimates; and deploy the best available technologies for LFG monitoring and reduction. Specific actions include to:
- Improve LFG collection at the Cedar Hills Regional Landfill (CHRL) by at least 5 percent per year (25 percent total) through 2030, compared to 2023. This will be accomplished through expanded vertical well installations and operational improvements. Related work at the CHRL includes completing an Investment Grade Audit (IGA) that provides a framework and vision for an optimal gas piping system that maximizes and optimizes gas and liquids collection and management while minimizing fugitive emissions. Additionally, pending the results and lessons learned from the phase one vertical gas well installations and the IGA, request funding for phase 2 well installations, with possible future budget requests if further GHG reductions are feasible from additional well installations. The SWD will also complete the Cedar Hills LFG collection “4 interior header” replacement project by 2025, which will increase LFG collection system reliability, reduce fugitive methane, and increase renewable biogas production.
- Reduce LFG emissions from SWD’s closed landfills by installing a new biofiltration cover pilot project in 2025 at the closed Duvall landfill to reduce LFG emissions and by including in future closed landfill environmental investigations scope to analyze potential productive uses of LFG collected at Hobart, Cedar Falls, and Vashon Island closed landfills.
- Optimize the production and use of LFG as a renewable biogas by continuing to monitor and improve the quality and quantity of LFG available for renewable biogas production and by evaluating areas of lower producing, lower quality LFG (both older sections of the CHRL and closed landfills) for potential productive uses.
- Continue testing and use of new technologies that improve the measurement and calculation of fugitive landfill emissions including by building on recent LFG drone monitoring efforts, which began in 2024, through use of a third-party contractor. Initial results from this effort have improved response times to LFG leaks and provided an improved understanding of LFG emissions locations. Building on this initial drone monitoring effort, the SWD will explore ownership and operation of a drone monitoring program.