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Dane County, Wisconsin Plans Bio-reactor Landfill

Wisconsin State Journal – Landfill will get longer life; bioreactor planned - by Ron Seely

With space left for just six years worth of garbage in the Dane County Landfill, officials are on the verge of re-engineering the 76-acre site to install a controversial system that will hasten the decomposition of waste and extend the operation of the facility by as much as 10 to 15 years.

But critics say the plan poses long-term threats to air and groundwater. And they worry that continuing to rely on the landfill has short-circuited a thorough discussion of how the region’s waste will be disposed of in the future. They say the county is missing an opportunity to move toward a future without landfills and to rely more heavily on recycling, including recycling of organic wastes such as food.

Dane County is not alone in its struggles with waste. Bill Casey, solid waste director for Columbia County and a board member of the Wisconsin Counties Solid Waste Management Association, said there are only 50 landfills, both private and municipal, operating in the state. Many of them are fast filling up, Casey said, so communities throughout the state are in the midst of discussions about where to put their garbage.

“We’re seeing this all over the state”, Casey said. “It’s a problem. It’s going to continue to be a problem. Every time we close a landfill, that waste has to go someplace else. These are going to be difficult decisions.”

Bioreactor planned

Meanwhile, county engineers are preparing to build a $2-million bioreactor at the Dane County Landfill, just east of Interstate 39-90 on Highway 12-18.

“Bioreactor ‘ ‘ is a fancy name for a system of pumps and pipes that will circulate water and air through the landfilled garbage and cause it to decompose more quickly, thus freeing up space for more waste, said Gerald Mandli, public works director for Dane County.

The new system, which may be in operation by next fall, basically turns the landfill into “a cooking vessel, ‘ ‘ Mandli said.

Use of the bioreactor turns the current science behind the landfill ‘s operation on its head. Since it went into operation in 1986, the object has been to keep moisture away from the garbage. In fact, the common name for the system in use at the Dane County landfill and most landfills across the country is “dry tombing. ‘ ‘

Currently, about 20,000 gallons a day of leachate — Mandli calls it “garbage juice ‘ ‘ — from decomposing garbage is pumped out of the landfill and piped to the Madison Metropolitan Sewerage District plant where it is treated and discharged along with other processed wastes.

To make the bioreactor work, that leachate would be recirculated through the landfill, along with air. The air and water both hasten decomposition.

Mandli said the bioreactor was approved by the County Board last year after it became apparent that the landfill was filling up faster than anticipated.

Tons of unexpected waste jammed the landfill in 2006 and 2007, from the homes destroyed and damaged by the Stoughton-area tornado in August 2005 and from the roofing materials replaced after a hailstorm in April 2006. The landfill took in 53,000 tons of shingles in the wake of hailstorms, Mandli said.

The bioreactor is still in the design stage. Mandli said the county is taking its time with the project so that all potential problems are addressed.

More methane

Chief among those problems, according to Peter Anderson, owner of Recycleworlds Consulting in Madison and a nationally-known expert on recycling and waste disposal, is the increased production of methane, a gas produced by the decomposing garbage.

Currently, methane gas is drawn by a vacuum system from the landfill and used to power generators that turn it into electricity. That electricity, enough to power 5,000 homes, is sold to Madison Gas & Electric for $1.2 million a year. More…

(Waster: This sounds rather like what we term in Europe a “Flushing” landfill. This treatment of a landfill is not permissible within the EU Landfill Directive. Also, the removal of high Landfill Gas yield is usually impeded by the greater extent of perched water tables and flooded gas extraction wells such that increased gas yields would not necessarily result from this treatment at all.)

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