Public Works

Biosolids Program

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The term “biosolids” refers to the solid organic matter residuals generated by the biological wastewater treatment process. These residuals, or biosolids, contain essential nutrients that when properly treated and processed can be applied as fertilizer to farmland, improving soil health and fertility and enhancing plant growth. Returning biosolids to farmland completes a natural food cycle where farms produce is consumed by humans who then produce biosolids, which, when treated appropriately to kill pathogens and enhance the fertilizer value, can be returned back to the farms to offset input costs and deliver remarkable yield results. This multi-use product can also be used for sod farming, soil remediation, horticulture, golf courses, and more.

Nutrient-rich treated biofertilizer products include predictable nitrogen, phosphorous and potassium values as well as a variety of micro-nutrients such as iron, zinc, magnesium and copper – all essential for healthy agriculture soil and plant growth. In addition to the rich nutrients, biosolids contain valuable organic matter which helps improve the overall health, structure and tilth of soil – something that cannot be replicated by synthetic, chemical fertilizers.

Class A Exceptional Quality Biosolids
To ensure maximum acceptability and safety, the City of Shelton treats biosolids to meet stringent standards imposed by the EPA for Class A Execeptional Quality (EQ) biosolids. The EPA classified Class A (EQ) biosolids can be sold for commercial and residential use without any special permitting. In order to achieve this EQ standard, the City of Shelton uses the latest fertilizer manufacturing technology to heat treat the biosolids and eliminate all disease causing bacteria.

The use of Class A Exceptional Quality biosolids as fertilizer for both residential and commercial use is endorsed by the United States Environmental Protection Agency (EPA). The EPA promotes biosolids based fertilizers as environmentally safe and beneficial for plant growth.


Regional Partnerships
As one of the only municipalities in the South Sound region capable of producing Class A Exceptional Quality biosolids, the City of Shelton has partnered with several local communities and businesses to process digested sewer sludge produced by other wastewater treatment facilities. Community partners include: Mason County, Squaxin Island Tribe, Skokomish Tribe, Washington State Parks, Alderbrook Resort, Yelm and Thurston County.

In 2017, the City processed over 1.33 million gallons of digested sewer sludge, which produced approximately 92 tons of Class A EQ biosolids. Revenue generated by the City’s regional biosolids processing program covers the cost of production, processing, operations, and facility maintenance.  

Class A EQ biosolids are available for pickup free of charge at the City’s wastewater treatment facility, located at 1701 Fairmount Ave, Shelton, WA 98584. Due to high demand, there is typically a 2 to 3 month waiting list.  Contact the City of Shelton Wastewater Treatment Plant at 360-426-6521 for details.