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Applying biosolids on farmlands

Loop® biosolids are a natural soil builder. Using Loop recycles the nutrients in our food back to the land, the same way nature does. It is an endlessly renewable resource that’s good for people, plants, and Puget Sound.

Farmers call Loop a “soil amendment”—and it’s made from the poop we all produce! After it’s been treated and cleaned, the finished product contains essential macro and micronutrients that boost plant growth. Rich in organic matter, Loop improves soil structure and acts like a sponge to help the soil hold water. Using Loop is a simple and easy thing to do to help plants—and the environment—thrive.

For more information on Loop, how it’s made, and how it can turn your dirt around, please visit


Managing King County's biosolids

The King County Biosolids Program manages Loop from the time it leaves our wastewater treatment plants to when it is spread on a field or forest. King County tracks every ton of Loop from start to finish. This includes transportation and delivery to our customers (at least 10 loads a day in our Loop trucks), permitting and using Loop, research and monitoring, and public outreach.

How much do we produce?

Each year, King County produces enough Loop to fill a football stadium 70-feet high, or about 120,000 tons. Most of this is used as a soil builder and fertilizer replacement for farms in eastern Washington or tree farms and forests in eastern King County. Loop is also used to restore landscapes and as an ingredient in a locally made compost for home gardeners and landscapers. 

The right choice for King County

Using Loop as a soil builder and fertilizer replacement is the most cost-effective way to use our biosolids. Because the benefits and safety of this practice have been demonstrated for decades, biosolids are considered a valuable commodity. The Washington State Department of Ecology requires they are recycled on farms, forests, and gardens, which also conserves landfill space. Returning biosolids to the soil where they have the most benefit to our communities is also the environmentally responsible thing to do.


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