Loop biosolids is a natural fertilizer and 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.

What is Loop®?

What are biosolids and how are they made? In this video, staff from King County Wastewater Treatment Division show how they transform raw wastewater into Loop® biosolids. After the transformation is complete, this endlessly resource is used to fertilize farms, forests, and gardens.

Loop 101

As it has for the past 40 years, King County produces Loop from solids (the food and poop) recovered during the wastewater treatment process. King County doesn’t just clean the water, we also create three renewable resources: Loop, biogas, and recycled water. Using Loop as a fertilizer and soil builder recycles the nutrients in our food back to the land, the same way nature does. Harvested plants take nutrients out of the soil, humans eat those nutrients through our food, and then we return nutrients to the soil with Loop.  Loop is an endlessly renewable resource restoring carbon and nutrients to the land for the good of plants, people, and Puget Sound.

Loop is awesome. The biogas produced when microorganisms break down the poop and the food into Loop is harnessed to create renewable energy. Choosing to use Loop as a fertilizer doesn’t just help the soil and plants, it also reduces greenhouse gas emissions into the atmosphere. Loop helps us fight climate change so much, it’s actually one of the main reasons the King County Department of Natural Resources and Parks is carbon neutral.

Loop also delivers all the macro- and micronutrients that plants need, making it a superior source of plant food over synthetic fertilizers. It has a proven ability to improve soil structure, which reduces runoff and erosion and protects local water quality. Held to rigorous standards by both the EPA and the State of Washington, Loop is safe.  It has enriched Pacific Northwest landscapes as an ingredient in the commercial product GroCo since 1976.

Take a tour of King County’s Wastewater Treatment Plants to see for yourself how Loop is made.