VERMICOMPOSTING PROJECTS
WORMING THE WAY TO FINISHED COMPOST
California firm grinds yard trimmings into “worm food” at a vermicomposting operation that processes up to 150 tons/day.

Each day, up to 150 tons of yard trimmings from five nearby towns are delivered to Ecology Farms in Perris, California just east of Los Angeles. “It’s all part of California’s ‘Clean Green’ recycling program,” says George Bodlak, operations manager at the 50 acre compost site. “We grind the material when it arrives to a half-inch mesh ... then feed it to the worms.”

When Bodlak first started at Ecology Farms, his primary interest was supplying worms (Eisenia fetida) — not making compost. But the company is no longer selling worms but concentrating on vermicomposting. About 95 percent of the yard trimmings are brought in by trucks operated by CR&R, a hauling and recycling company that services communities in the fast-growing southern end of Riverside County.

Currently, Bodlak estimates that more than one-half million pounds of worms are helping to break down organic feedstock in the 10,000 linear feet of windrows. “The windrows are 12 to 14 feet wide, and we start them out at about one foot high,” Bodlak explains. “When they get up to 3-1/2 feet high, we consider them finished — roughly three months after windrows were formed. Breeding enough worms to get vermicomposting under way is the expensive part of the process,” he adds. “You need a large enough herd of worms to process the green feedstock. To work well, I estimate that one pound of composting worms is needed per cubic foot.”

Since windrowed materials are kept very wet to allow worms to be active, moisture content needs to be lowered in the finished compost. During summer, the windrows tend to dry up in less than a month, but during rainy winter season, drying out takes longer.

SCREENING AND GRINDING

When materials from CR&R and other generators are unloaded, a preliminary screening separates out nonorganic contaminants. Even though there are source separated programs in places like Temecula and Lake Elsinore, there is the occasional appearance of plastic and glass that needs to be sorted out. Next, Bodlak’s crews put materials through a Vermeer tub grinder that can process up to 200 tons (or 720 cubic yards) a day.

After the initial grinding, water is sprayed onto the piles, and two days later, the grinding process is repeated — this time through one-inch screens to produce a much finer material that can be spread onto windrows as “worm food.” As the Eisenia fetida process the green waste, they continually move up in the windrow. “That’s what distinguishes these redworms from the common earthworms that tend to move down into the soil,” Bodlak points out. “As long as the redworms have moist feed on top of them, they keep eating, breaking down material and reproducing.”

When the windrows reach the three feet level, the worms in the top six inches are “scooped up” with a loader and deposited in a newly-formed windrow. The vermicompost in the finished windrow is allowed to dry, then screened to a half to 7/8th inch. The product is sold in bulk to soil blenders, who in turn do the bagging for varied uses. m

Some information for this report on Ecology Farms was provided by Richard Yach, a freelance technical writer.