Who turns their dirt around with Loop?

Boulder Park Inc.


Thanks to Boulder Park, Inc., many farmers and landowners have already reaped the benefits of Loop. Boulder Park is a farmer-owned company managing the distribution and use of Loop in Douglas County. Since 1991, farmers who’ve amended their soil with Loop have increased crop yields, decreased fertilizer costs, reduced erosion, stored carbon, and helped replenish the soil for thousands of acres of dryland grain crops.

Visit Boulder Park for more information.

Natural Selection Farms, Inc.


Natural Selection Farms, Inc. is a third generation family farming operation on the southern side of Snipes Mountain in Yakima County, WA. They believe holistic farm management practices should be used to promote crop growth and maintain harmony with nature. Natural Selection Farms has been committed to returning carbon and nutrients in biosolids to soils since 1980. Their use of Loop has reduced the use of synthetic fertilizers and pesticides on thousands of acres of canola, hops, alfalfa, wheat, orchards and managed rangeland.

Visit Natural Selections Farm for more information.

Snoqualmie Forest


Snoqualmie Forest has been fertilized with Loop since 1987. Every year, Loop supplies about 1,000 acres of timberlands with nitrogen and other essential nutrients to help trees grow. Loop substitutes for commercial fertilizers while enhancing soils and wildlife habitat. Learn more.

Washington State Department of Natural Resources (DNR)


Loop is used to improve soils and fertilize trees in state forests in King County, primarily in Marckworth Forest near Duvall. King County partnered with DNR in 1995 as part of the Mountains to Sound Greenway biosolids forestry program. Loop helps store carbon in wood and forest soils. Learn more.

Alleycat Acres


Alleycat Acres is a Seattle-based urban farming collective that converts vacant lots into community-run farms. By farming the cityscape Alleycat Acres is addressing a number of issues facing our communities. Members of the collective agree that it makes sense to use GroCo compost made with Loop to condition and fertilize city dirt into fertile soil. Not only does GroCo help them grow lots of nutritious fruits and vegetables, Alleycat Acres is doing their part to close the nutrient loop.

Visit Alleycat Acres for more information.

City Soil Community Farm Project


As part of a four-way partnership between King County Wastewater Treatment Division, Seattle Tilth, King Conservation District, and DIRT Corps (Duwamish Infrastructure Restoration Training), King County manages a small demonstration farm at the South Treatment Plant in Renton. City Soil Farm was once an unused area of the treatment plant’s grounds, but has been transformed into a teaching farm and native tree nursery. This project showcases the benefits gained with use of GroCo compost made with Loop and recycled water in sustainable farming. The food grown at City Soil is accessible to everyone: volunteers and students can harvest the food as they learn or tend to the farm, extra food is donated to local food banks, and every year produce is donated to the King County CHOMP dinner, where local Seattle chefs prepare a five star meal to raise money for a local non-profit.

Courtnee from DIRT Corps explains why City Soil is such a cool project:

“City Soil is a really unique project. It’s on the wastewater treatment plant’s facility. It uses renewable resources. It’s a community space where people can come and learn about how their food is grown, and taste the food, and take some food home.”

Come visit us at CitySoil Farm.

Who can help you turn your dirt around?

GroCo, Inc.


GroCo, Inc. has been recycling carbon and nutrients by composting Loop with sawdust since 1976. GroCo compost made with Loop is composted for over a year resulting in a mature, clean, weed- and pathogen-free soil amendment that looks and smells earthy, much like a forest floor. GroCo compost is ideal for use in residential and commercial landscaping, home vegetable gardens, and soil restoration.

Visit Sawdust Supply, Inc. for more information.

Who are friends of Loop?

Northwest Biosolids


Northwest Biosolids is a cooperative of public wastewater agencies, sewer districts, and private companies in Washington, Oregon, Idaho, Alaska, and British Columbia. Northwest Biosolids’ mission is to advance environmental sustainability through the beneficial use of biosolids. With the support of its members, Northwest Biosolids provides continuing education and networking opportunities, produces publications, reviews biosolids regulations and funds university involvement and research.

Visit Northwest Biosolids for more information.

Mountains to Sound Greenway Trust

Mountains to Sound Greenway Trust mountain view

The Mountains to Sound Greenway connects natural areas, trails, working farms and forests, historic towns and communities, wildlife habitat and recreation opportunities from Seattle across the Cascade Mountains to Central Washington. The Mountains to Sound Greenway Trust facilitated an agreement between King County and private and public forestland owners to use Loop to provide nutrients and preserve Greenway forests, as well as restore degraded natural lands. The Trust provides outdoor science education – featuring Loop – for forest field study trips to students.

Visit Mountain to Sound Greenway Trust for more information.


Islandwood (3)_612

Founded in 1999, IslandWood is a nationally recognized environmental education organization connecting thousands of children and adults every year to the natural world in communities throughout the Puget Sound region. IslandWood’s mission is to provide exceptional learning experiences and to inspire lifelong environmental and community stewardship. The partnership between King County’s Brightwater Center and IslandWood is leading the way to new and enhanced educational programs for area students, teachers, and community members. The partnership enables the expansion of educational programs currently offered at the Brightwater Center to students in the third through eighth grades, including teacher trainings, adult workshops, family programs, and summer camps.

Visit Islandwood for more information.

King Conservation District


King Conservation District is a special purpose district that serves most communities in King County.  We help residents steward their natural resources through education, technical assistance, and funding.  King Conservation District is proud to partner with the King County Wastewater Treatment Division in supporting City Soil Farm, a working urban farm at their south King County treatment plant, and to help neighborhood organizations develop community gardens through peer-to-peer learning, workshops, project coordination, and site facilitation.

King County has a partnership with King Conservation District to provide GroCo compost made with Loop to King County community gardens and urban agriculture each year, as part of a pilot program.

Visit King Conservation District’s urban agriculture program page for more information.

Seattle Tilth


Seattle Tilth has been teaching people how to grow food using organic and ecological principles and techniques since 1978. Our education programs focus on the full spectrum of the food system: the earth, farms, gardens, markets and kitchens. We emphasize hands-on learning for all ages and our programs encourage people to take action at home and in their communities to build a sustainable and equitable food system. In 2016, Seattle Tilth merged with Tilth Producers and Cascade Harvest Coalition, which has strengthened our farm and market programs and has allowed us to expand our services statewide.

Seattle Tilth began managing the City Soil farm in 2016 as a way to demonstrate the role of recycling wastewater and to explore the use of biosolids in sustainable food production. All the food grown at the farm is donated to local food banks and used for educational programs.

Contact Seattle Tilth if you are interested in volunteering for this project.

Duwamish Infrastructure Restoration Training (DIRT Corps)


Duwamish Infrastructure Restoration Training (DIRT Corps) provides on-the-job training for young adult workers, specifically encouraging women, people of color, and un/underemployed adults to join and then lead. The program provides stipends to a crew that works year-round as part of a quarterly curriculum program that includes classroom and hands-on training.  With a focus on equity and environmental justice, DIRT Corps teaches rain garden and cistern design/build, operations and maintenance (O&M), urban forestry, vegetation management and ecological restoration.  At City Soil, DIRT Corps training includes using reclaimed water and GroCo compost to grow out tree species for a free tree giveaway program to enhance tree canopy in South Seattle and nearby areas of Unincorporated King County.

Visit DIRT Corps for more information.