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New Pr 1A53 ocess Speeds up Landfill Waste Breakdown

A University of Georgia engineer, a private engineering firm and operators of a Metro Atlanta landfill have developed a process that could reduce the amount of landfill space needed to meet Georgia's needs.

S. Omahen, UGA CAES
Smith (r) and Brown check well pressure at the test 
site.

PUMPING WATER AND AIR into landfills can help the material in them decompose more quickly, say University of Georgia scientists. Matt Smith, right, checks the pressure of a well pumping water into the test landfill site at Live Oak Landfill with the help of Hughe Brown. This process, when combined with removing recyclable materials, can recover 75 percent to 90 percent of the space in a landfill.

Traditional landfills are designed to keep air and water out. The new process involves putting them in.

The old way

"Normally, organic waste is piled up, the microorganisms begin to work and in the process, they deplete the oxygen," said Matt Smith, an agricultural engineer with the UGA College of Agricultural and Environmental Sciences.

"The waste degrades slowly," Smith said. "And unfortunately, methane gas is produced."

Landfill operators must collect the gas and either burn it off or compress it for use as an alternative fuel.

"Modern landfills are also lined to keep the leachate water from getting into groundwater," Smith said. "This water has to be treated before it's sent to the local water treatment plant."

The new way saves space and protects the environment

Handling the methane gas and leachate water are costly processes for landfill operators. Smith and engineers from the firm of Arcadis, Geraghty and Miller developed a process that uses air and water to speed up the decomposing.

"We reinject the waste with the leachate water and additional fresh water and pump air into the waste," Smith said. "The extra water and air feed microorganisms that work much quicker at decomposing the waste."

Testing in Georgia

The engineers tested the new process with their project partners at Waste Management, a national firm that operates waste treatment facilities nationwide.

Using a 2.5-acre, 30-foot-deep waste site at the Live Oak Landfill in DeKalb County, Ga., the team proved the new process works.

"The waste settles much, much quicker. In the long run, that results in more space for landfill operators," Smith said. "Just 12 weeks into our first test, we recorded 6-percent settlement."

The new process also produces less methane. The methane levels on the pilot site were up to 90 percent lower than those in traditional landfills.

"Our main 207-acre site takes in more than 5,000 tons of solid waste each day," said Hughe Brown, special projects manager at the Live Oak Landfill. "Landfills typically have a life of 20-30 years, depending on the volume of waste in the area."

Good, but pricey to start

The process expands the life of the landfill. But the startup cost is high.

"It cost Live Oak Landfill $2 million to test the process. So it's quite an investment," Smith said. "But the result is a much more environmentally friendly landfill than we traditionally see."

Other benefits include easier recycling

More landfill space isn't the only benefit. The process results in stable organic material that can be sorted and sold or given to recycling companies.

"What's left are plastics, wood, cement, glass and other stable materials," Smith said. "Once you've mined and separated the remaining materials, you can market them."

Some of these materials might be sold. Others are given away. Either case makes more landfill space available for reuse.

Stages increase landfill life

S. Omahen, UGA CAES

LandfillBy using the new process, then mining the remaining materials, a landfill could recover 75 percent to 90 percent of its space, Smith said.

"The key is to use the process in stages throughout the landfill," he said. "You fill in one area while you're decomposing another. In the end, you've increased the life of the landfill. And you've created a much more stable landfill in the process."

(Sharon Omahen is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)

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