loop

Loop biosolids is 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.

FAQ: How is Loop made?

Every day you make a donation to us to grow plants somewhere in the state of Washington. It all begins in your house when you turn on your tap and flush your toilet. King County takes care of the rest. After the cleaning process is complete, the result is Loop biosolids, a nutrient-rich soil builder that plants love. 

Loop 101

As it has for the past 40 years, King County makes Loop biosolids from solids (the food and poop) that we remove in the wastewater treatment process. Gravity separates the solids from the liquids, and then we treat and clean both the liquids and the solids using engineering technology. This engineering technology uses microorganisms from our own bodies, and mimics nature’s cleaning powers to keep our cities, landscapes and waters healthy. The end result is Loop, a nutrient-rich soil builder. Using Loop 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 the nutrients are returned 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 grounded in rigorous science. Held to strict standards under the Clean Water Act, we continuously research and test Loop. For nearly 40 years, we’ve built on Environmental Protection Agency and other national data and worked with university scientists to study how well Loop works.

See how Loop is made

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

What is Loop? How Is Loop made

Loop has enriched Pacific Northwest landscapes as an ingredient in the commercial product GroCo compost since 1976.