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Learn more about biosolids and how they return essential nutrients to soil for healthier, more productive farm crops and forest trees.

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Our Biosolids Program oversees agriculture and forestry projects and new product development for Loop®, the nutrient-rich organic fertilizer alternative and a natural soil builder created from King County's wastewater. As the longest running biosolids program in Washington state, we manage Loop from when it leaves our wastewater treatment plants to when it’s used on farmland and forest floors.

We track every ton of Loop from start to finish, including transportation and delivery, regulatory requirements, monitoring, and public outreach. Our program has a long, successful history of partnering with customers and researchers to ensure 100% of Loop is distributed for beneficial use.