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Since it began, the King County Biosolids Program has worked with soil scientists at local and regional universities to develop and test biosolids product quality and applications.

Our research partnerships serve as the foundation of our program, and we’ve gained a reputation in the industry for our scientific research practices. At our Boulder Park Project, we even have one of the longest-running (more than 25 years!) biosolids research projects in the nation. 

Studies conducted there by Washington State University soil scientists have confirmed that fields enhanced (or amended) with biosolids produce crop yields equal to or better than those treated with synthetic fertilizer. Repeated biosolids applications produced significant long-term increases in soil carbon, which builds the soil and helps us fight climate change

We believe these ongoing research partnerships are key to effective third-party review and oversight of Loop® biosolids. The partnerships allow us to track the benefits of Loop and provide quality assurance for landowners and our customers who use Loop. They also help us explore new uses and markets for Loop.

Our key research partners include:

Here are a few of our ongoing biosolids research partnership projects:

Combating Wind Erosion in Eastern Washington

Dust devils are common in Eastern Washington, where the wind can blow away large amounts of topsoil. Feedback from farmers suggests that biosolids reduce wind erosion. This research is being conducted to evaluate the potential for wind-borne soil particles and to quantify whether biosolids help reduce wind erosion. Results from research on airborne particles and pathogens will also help inform farmers and local governments in eastern Washington that are considering using biosolids. 

Research Partners: Washington State University , U.S. Department of Agriculture – Agricultural Research Services

Examining Phosphorus Runoff in Eastern Washington

Because phosphorus runoff from agricultural soils is an major environmental threat, the Conservation Stewardship Program and other assistance conservation and farming programs through the U.S. Department of Agriculture (USDA) limit the use of phosphorus fertilizer for program participantson certain lands. Through the work of this research project, WTD’s Loop biosolids’ agriculture program, and dedicated biosolids customersfarmers, USDA Natural Resources Conservation Service is working with farmers landowners to allow use biosolids in a way that meets the environmental goals of applications in way that meets program goalsthe Conservation Stewardship Program.

Research Partners: Washington State University , Oregon State University

Studying Bioretention Soil Mixes

Green stormwater infrastructure (GSI), such as rain gardens and bioswales, help communities—especially cities and counties with combined sewer systems—manage stormwater and protect our rivers, lakes, and Puget Sound. Current guidelines for compost use in GSI projects are based on what a compost mix (called compost feedstock) is made of, and compost mixes made with biosolids or manure are not currently allowed. This study is evaluating whether a performance-based standard could be consistently used across all compost feedstock types, including compost made with biosolids.

Research Partner: University of Washington

Trace Organic Compounds Risk Analysis

Although research to date shows that biosolids are safe, there have been questions about the trace amounts of chemicals from pharmaceuticals and personal care products that wind up at treatment plants, also called trace organic compounds. Compared to daily use of these common products, this analysis determined the amount of these chemicals in biosolids is incredibly small and presents negligible risk. It would take many lifetimes (or many thousands of lifetimes) of working around biosolids to get just one dose of many of these medicines. 

Research Partners: University of Washington , Kennedy/Jenks

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