Compost: Closing the loop on urban garbage and local farms

Commercial compost is spread at a Snohomish County farm. (Photo by Andrew Corbin, WSU)

By Sylvia Kantor, College of Agricultural, Human & Natural Resource Sciences

SNOHOMISH COUNTY, Wash. – Compost produced from urban food and yard waste could be “black gold” to farmers wanting to increase their yields and profits while improving soil and water quality. Washington State University Extension in Snohomish County is exploring how urbanization, long considered a threat to local agriculture, might actually help farmers keep up with demand for local food while recovering a valuable resource from the urban waste stream.

Feeding soil with urban waste

In 2008, as the economy slowed and construction and landscaping budgets shrank, compost producers like Cedar Grove, with facilities in both King and Snohomish counties, found their product piling up.

“Cedar Grove approached us in late 2010 to explore the possibility of selling surplus compost to agricultural markets. So we did some initial research trials on a shoestring budget,” said Andrew Corbin, agriculture and natural resources educator with WSU Snohomish County Extension. The trials documented the effects of applying commercial compost in crop production on three farms.

What Corbin discovered was a dramatic impact on yields. For two years in a row, pumpkin yield increased by 20 percent and triticale showed a 100 percent increase.

“With the potential to increase production of some specialty crops by 20 percent, this could have a significant economic impact on Washington’s specialty crop industry,” he said.

Commercial composters in King and Snohomish counties that accept food and yard waste from curbside collection programs produce compost on a large scale – sometimes more than they can sell for use in urban landscapes. Having to store surpluses of finished compost can be a problem for local air and water quality.

At the same time, with fewer local dairies to supply nutrient-rich manure, many specialty crop growers are interested in using compost. But few can produce enough of their own to meet the nutrition needs of their crops; they often must rely on soil inputs produced outside the region.

Seeing is believing

In addition to the formal research trials, Corbin partnered with Cedar Grove and the Snohomish Conservation District to offer free loads of compost to 38 growers to try on their crops and assess the benefits for themselves.

Growers like Reid Carleton of Carleton Farms and Dana Young of Lucky Dove Farm were impressed with what they saw.

“We had earlier emergence of pumpkin plants,” Carleton said. “They were healthier, they grew faster and with the rapid (leaf) canopy that was established, it really helped with weed control. And we got better pumpkins and more of them.”

“Everything grew taller and greener,” Young said. “Broccoli heads and side shoots were twice as big as those on plants without the compost added.”

Mind the gap

Corbin hopes his project will help close the gap between what farmers are willing to pay for compost and the price compost producers are asking.

Commercial facility in Snohomish County produces compost from urban food and yard waste. (Photo courtesy of Lenz Enterprises)

Lenz Enterprises, which produces Greenblenz compost products, recently was awarded a contract with the City of Seattle to compost up to a third of the city’s curbside food and yard waste and is excited to participate in the WSU study.

“I think we’ll be able to find a middle ground on price,” said Taylor Brown of Lenz Enterprises. “That’s part of the reason we’re getting involved – to see what farmers are looking for and where we can meet them.

“We’re near farms right here in Snohomish County, so it makes sense to harness that market and return the material back to the soil. It’s marketing and it’s the right thing to do,” Brown said.

Research expansion

“No research like this has ever been done in western Washington,” Corbin said. “This is the largest single county project documented in the country.”

A recently awarded $200,000 U.S. Department of Agriculture specialty crop block grant will support the three-year Snohomish County agricultural compost research and outreach project (SCACROP). It will include six research trials to evaluate yield, soil properties, water infiltration and other properties and up to 75 demonstration trials with farmers in Snohomish and northern King counties. It also will involve more commercial composters like Lenz Enterprises and Bailey Compost.

With growing interest in local food production as well as concerns about the use of chemical fertilizers and increasing urban waste streams, farmers and commercial composters across the country will be eager for the results of this research.

Additional support for SCACROP research is provided by Snohomish County’s Surface Water Management Division and Economic Development Team, Snohomish County Solid Waste Division, Snohomish County Office of Energy and Sustainability, the Snohomish Conservation District, King County Solid Waste Division, Waste Management Inc., Lenz Enterprises, Bailey Compost and Cedar Grove Composting Inc.

To participate

Farmers in Snohomish County or northern King County interested in participating in the 2014-15 compost trials may contact Hallie Harness at 425-357-6026 or




Andrew Corbin, WSU Extension, 425-357-6012,

Sylvia Kantor, WSU CAHNRS Marketing, News and Educational Communications, 206-770-6063,