Survey of Large Commercial Compost Facilities in Washington

This report summarizes a survey of the ten largest commercial composting facilities in Washington state, conducted to support development of improved methodologies for measuring air emissions from compost operations. The study was commissioned through the Waste to Fuels Technology Partnership and carried out by Washington State University researchers in coordination with the Washington State Department of Ecology.

Facilities were surveyed regarding feedstock composition, composting processes, aeration systems, and emission mitigation strategies. The findings document substantial variability across facilities, including differences in mechanical aeration approaches, use of biofilters, seasonal feedstock changes, and process configurations such as windrows, covered aerated static piles, and reversing aeration systems.

Results highlight implications for measuring volatile organic compound (VOC) emissions, noting that traditional surface flux isolation chambers may not capture emissions from negatively aerated or reversing systems. The report provides preliminary recommendations to inform future field testing and development of standardized emissions sampling protocols for Washington composting facilities.