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Loop® is our biosolids product. It is an endlessly renewable resource. For over 40 years, it has recycled the nutrients in our food back to the land the same way nature does. Loop is a fertilizer alternative produced by cleaning, recycling, and transforming King County’s wastewater into biosolids. We use it on farms and forests to generate healthier, more productive soil that increases crop yields and boosts tree growth. As a natural soil builder, Loop improves soil structure and acts like a sponge, helping soil retain water and nutrients for plants while preventing runoff into rivers and streams.

The Washington State Department of Ecology classifies biosolids as a beneficial resource and requires wastewater treatment facilities to keep biosolids out of landfills. We continue the legacy of using 100% of Loop.

Loop map in Washington

Learn more about Loop’s history and diverse distribution here .

For more information about Loop and its positive impacts visit

For more information about Loop biosolids, please contact us at: