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Biosolids Recycling

For more information about the Biosolids Recycling Program, please send us an email message or contact us at: 

King County Wastewater Treatment Division
Resource Recovery
201 S. Jackson Street
Mail Stop: KSC-NR-0512
Seattle, WA 98104
Phone: 206-477-5557
Fax: 206-684-2057

Biosolids compost for gardens

GroCo biosolids

Compost made with biosolids is a safe and effective soil amendment. Loaded with nutrients and organic matter, biosolids compost builds healthy soil, retains moisture, and produces lush plants and beautiful blooms. Use biosolids compost in flower and veggie beds, on lawns, or around trees and shrubs.

What is GroCo compost?

Three parts sawdust and one part biosolids are blended and composted for a year to create a fine-textured 'exceptional quality' biosolids product. GroCo made with Loop biosolids has been marketed in greater Seattle area since 1976 and has a loyal following among commercial landscapers and home gardeners.

GroCo made with Loop is now Declare certified, meeting Living Building Challenge (LBC) standards. LBC is the built environment's most rigorous performance standard. 

Where can I get GroCo compost?

It is available throughout the greater Seattle area and at Sawdust Supply, Inc., 6314 7th Avenue South, Seattle, 98108.

King County contracts with a local private company to make GroCo.
For information: 206-622-5141

Download a GroCo Brochure  (PDF, 1.7 MB)


Local Soil - an article in BioCycle Magazine by Dr. Sally Brown, UW 

Dow Constantine with GroCo at Earth Day 2010

King County Executive Dow Constantine with GroCo biosolids compost at Earth Day 2010 celebration.

Holding GroCo
"Growing despite the cold & rain"
"Why I love biosolids"
urban food producer blog

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