Mixed waste composting review


Courtesy of BioCycle Magazine

COMPOSTING mixed muncipal solid waste (MSW) is an attractive solution for many communities that want to diver organics from landfills, but don't have the poplation 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 tibs/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 sophistricated screeing 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 compositing facility in Delware County New York iscolocated with a landfill, and Susan McIntyre agrees that this is significant. 'Quite a few muncipalities tour our MSW composting facility and are interested, but it's difficult to determine how viable it would be fir them,' says McIntyre, Solid Waste Director of the Delware 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 depending on tip fees to make revenue or meet payroll.'

Sevierville, Tennessee recommitted to MSW composting after its facility burnt to the ground in 2007. The recently reopened plant is also co-sited with a landfill. Tom Leonard reflects on the decision to rebuild. 'Sure, it's a challenge to make something out of what most communities just bury,' says Leonard, Solid Waste Manager for the City of Sevierville. 'While rebuilding the facility, we buried our waste in the landfill, and it was definitely a lot easier than the composting process. But now that our system is running again, we are making something of that waste.'

This year's BioCycle survey found only one request for proposal (RFP) for a MSW composting facility, in Gillette, Wyoming. Table 1 provides summery data for the 12 facilities in the U.S. Updates on each facility are bloew.

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