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MANAGEMENT of municipal yard trimmings has an intriguing history. Not too long ago, attention was focused primarily on leaves, and high tech methods essentially entailed use of a windrow turner. While many of today's facilities continue with a simplistic approach, a growing number of communities and private operators are taking on bigger challenges in terms of the materials they are processing, the scale of the operation or the aggressive focus on end markets.
This year's report on Yard Trimmings Management also reflects the confidence that both public officials and private sector operators have gained over the years. That confidence provides the basis for facility expansion, innovative public/private partnerships and a desire to move beyond leaves and grass to achieve higher levels of diversion.
ADDING INDUSTRIAL RESIDUALS
The Blue Stem Solid Waste Agency in Cedar Rapids, Iowa, started operating a composting facility in October, 1990, just prior to the state's disposal ban for yard trimmings. The facility processes 22,000 tons/year of yard trimmings, but the agency plans to triple throughput by composting industrial organic residuals. "Iowa has a 50 percent waste reduction goal, and three-quarters of the Cedar Rapids waste stream is commercial and industrial--so we are trying to aggressively go after the organic fraction," says Dave Hogan, director of Blue Stem.
Hogan believes he has the perfect recipe, involving two commercial generators. The facility has started taking residual sludge (i.e. unusable short fibers) from the recently opened Cedar River Paper plant on a pilot basis. The recycled corrugated cardboard mill is scheduled to double its production in 1997, bringing total paper residuals to 2,300 tons/month. The fibers consist of about 50 percent solids, have a brownish tint, and resemble blown insulation, Hogan says.
With this high carbon feedstock, the operation needs a nitrogen source. Genencorp International, a biotechnology firm that produces detergent additives and other products, fits the bill, Hogan adds. The company generates about 25,000 tons/year of organic residuals, similar to a fermentation by-product. "We have tried it in windrows, and it accelerates the process nicely," Hogan says. "It is high in nitrogen, which makes it a perfect mix with the fibers."
Adding these two industrial feedstocks to the yard trimmings could increase the total throughput at the composting facility to about 75,000 tons/year....