How a Family-Owned Business in the South End Turns Food Scraps Into Compost

Each week, many King County residents participate in a ritual: They take bags of food scraps to the green waste dumpster or roll their compost bin to the curb. About 18 months later, the banana peels and apple cores that were thrown in the compost will be the ingredients in a bag of Cedar Grove compost. Cedar Grove, which processes much of King County's green waste into compost at a site in Maple Valley, is roughly 30 minutes from Rainier Beach. Its headquarters are in Georgetown.

"I'm in a third-generation family business," said Stephan Banchero III, president of Cedar Grove. His grandparents were Italian immigrants who settled in Beacon Hill's established Italian immigrant neighborhood in the early 1900s. In the 1930s, "garbage was not a very lucrative business, and nobody wanted to pick it up, so the Italians got together and created a company to collect it," said Banchero. His grandfather, John Banchero Sr., along with Alfonso Morelli and Josie Razore, founded Seattle Disposal in 1938, a company that spun off other companies, like Rabanco (Razore-Banchero Company). Banchero grew up with the industry all around him. His father, Stephan Banchero Jr., is Cedar Grove's CEO.

In the 1980s, as Seattle worked toward decreasing the amount of garbage sent to landfills, the City approached the company to start a composting program for residential yard waste. 

"The City said they'd bring 5,000 tons of yard waste to the property, [which] our grandparents purchased in Maple Valley," said Banchero. "They arrived with 50,000 tons of yard waste from residents in 1988." Banchero's father and his team traveled throughout the country and Europe to study the best available control technology for composting. In 2008, Cedar Grove began taking non-cooked vegetative scraps. In 2011, the company began taking all food waste, including cooked foods and meats. 

In 2022, Washington State passed the Plastic Product Degradability Act, which required certification and proper labeling of compostable food service products, like cups, plates, and to-go containers. "Words like 'biodegradable' and 'degradable' on an item don't mean it can be placed in the compost bin," said Jay Blazey, Cedar Grove general counsel. Certified compostable products now have green, beige, or brown markings and include a certification stamp.

Currently, the Maple Valley site receives more than 200,000 tons of raw material, known as "feedstock," a year, which it turns into roughly 100,000 tons of compost. 

Here's what happens to tons and tons of kitchen scraps and yard waste.

First stop for food scraps is the tipping building, where green waste is "tipped" out of trucks. Gabe Morelli, Cedar Grove Maple Valley operations manager, can watch what comes in on a monitor from his office. In the photo above, Morelli takes larger contaminants out of the feedstock that just arrived at the site.

About 80% of the feedstock is from residential contributions, and feedstock, from any source, can contain contaminants, including plastic bags, plastic bottles, and plastic gloves. Sometimes people put their garbage in the compost, which needs to be removed. Cedar Grove doesn't accept glass because it's a safety risk in compost material. Pet feces is a pathogen risk and isn't allowed in compost bins. "Contamination is a problem," said Banchero "[The compost] is only as good as the material that you receive."

Cedar Grove adds carbon and water to raw feedstock material and, if needed, nitrogen. The feedstock is piled into mounds where it sits covered with an inch of organic composting byproduct for about 20 days. This cover insulates the pile, mitigates odor, and detracts rats, seagulls, and other animals.

After about 20 days, the material heads down a covered conveyor belt to "the pie," an area of partially decomposed mounds that are shaped like pie wedges. This area operates with an air-circulation system that captures the smells and ammonia emitted by the feedstock. The material is aerated in the pie for about another 40 days.

Compost sites like Cedar Grove are regulated by multiple levels of government. Inspectors routinely test for odors and check filters, maintenance, water-management practices, and more. Each month, a sample of finished compost material is tested by a third-party lab for pathogens, heavy metals, and inert materials, like plastic.

Cedar Grove uses another alternative compost-processing method at Maple Valley for the first 60 days called the Gore cover system, where feedstock is covered with a specialized cloth and the temperature and oxygen in the system are managed with fans.

The feedstock then moves from the pie to the "kraken," where the material is sifted through a screening system. The kraken uses magnets to remove metal, while more than 20 suction heads vacuum out plastic film.

Nick Blanchette, Cedar Grove Maple Valley facility manager, says the composted material is separated into three categories, based on size: large organic matter, like stubs of branches; inch-long bits; and fine material called "fines." Fines are sent to mounds that cure for 12 to 18 months. The oversized material can be ground up or used as cover for new feedstock.

After the fines finish curing, they're sifted once more and become finished compost. The majority is used by public agencies, some of which mix it with sand for landscaping projects. A portion is bagged to sell in stores for people to amend garden soil. 

Morelli said he's moved by working with a process that doesn't waste anything. "If you work in sand, gravel, and rock quarry, there's always a waste product," he said. Morelli described how all organic matter that's too big to be composted is recycled back into the system to break down more. "We're micro-farmers. All we really do is add air and water. We screen it, we size it, and Mother Nature does the rest. Then we put it back."

Got an idea for a South End story you'd like to see us cover? Let me know: Yuko.Kodama@SeattleEmerald.org.