Mixed Waste Composting Review

Twelve facilities composting mixed municipal solid waste in the U.S. continue to fill a niche, turning difficult waste streams into useful product.
By Rhodes Yepsen, BioCycle November 2009, Vol. 50, No. 11, p. 23

COMPOSTING mixed municipal solid waste (MSW) is an attractive solution for many communities that want to divert organics from landfills, but don’t have the population density to support a source separated organics (SSO) scheme. These facilities are capital intensive and not always successful, however. About half of the facilities constructed in the U.S. in the last 25 years have closed, with only 12 remaining. Most recently, the plant in Cobb County, Georgia, built to process 200 tons/day of mixed waste, was converted into a materials recycling facility (MRF).

“In the European Union we’re seeing a push for biomechanical waste processing, but that’s in response to mandatory landfill diversion goals,” says Robert Spencer, an environmental planner who helped start up a few MSW composting facilities, including Cobb County. “Without a mandate, economics rule, and right now there aren’t many places in the U.S. with the right conditions.”

Ultimately, the success of MSW composting facilities comes down to site-specific circumstances, such as area landfill fees, local government commitment and possible markets for MSW compost. “There are several variables that can be controlled, such as installing sophisticated screening technology,” says Spencer. “Also, the most successful plants in the U.S. are co-sited with a landfill, which allows for internalized residuals disposal cost and a destination for possible off-spec compost as cover material.”

The MSW composting facility in Delaware County, New York is colocated with a landfill, and Susan McIntyre agrees that this is significant. “Quite a few municipalities tour our MSW composting facility and are interested, but it’s difficult to determine how viable it would be for them,” says McIntyre, Solid Waste Director of the Delaware County, Department of Public Works. “We are uniquely advantaged — isolated, high organics waste stream content, and we can control the waste because we own-operate the adjacent landfill, meaning we aren’t dependent on tip fees to make revenue or meet payroll.”

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