Columbia seeks alternate energy source: trash

Tuesday, October 30, 2007 | 7:49 p.m. CDT; updated 7:45 a.m. CDT, Tuesday, July 22, 2008

COLUMBIA — Wind energy currently supplements Columbia’s non-renewable energy sources, but the future of green energy might arise from a more pungent source. Two “gas-to-energy” projects are under way at the Columbia Sanitary Landfill that will catapult the city far beyond its 2008 alternative energy target.

Generators are expected to be delivered Wednesday to the Landfill Gas Plant, a project the Public Works and Water and Light departments have joined forces to build, said Richard Wieman, solid waste utility manager. The plant, which is expected to become operational in January 2008, will convert gasses emitted from waste into energy, with the potential to produce an estimated 1.5 percent of Columbia’s total energy needs, according to a report by the Water and Light department.

That number will grow as more trash is added to the landfill, but the initial figure alone comes close to the 2008 benchmark of using 2 percent green energy mandated by voters in the 2004 Renewable Energy Standard.

Additionally, the Public Works department is constructing a bioreactor, which will speed up the decomposition of trash, generating gasses more quickly.

Coupled with wind energy and energy from landfill gas purchased from Jefferson City, alternative energy sources are expected to supply 5 percent of Columbia’s need by next year.

The voter mandate does not require Columbia to reach 5 percent until Dec. 31, 2012, and city officials are excited about the project that will help put them ahead of schedule.

“It’s a fascinating thing,” said Michael Symmonds, director of the landfill. “There’s more to it than just digging the hole and throwing the trash in.”

How can trash power your television?

When waste decomposes, it releases methane, a greenhouse gas the Missouri Department of Natural Resources requires to be contained or disposed of without harming the atmosphere. The Columbia Sanitary Landfill has been collecting the methane, also called landfill gas, with a system of tubing through landfill cells since 1993. It has never before produced enough gas to convert into electricity. Gas levels are nearing the usable mark, though, and methane production is expected to reach the necessary level by the beginning of next year.

Symmonds said that currently the methane is burned off, or flared, but with the construction of the Landfill Gas Plant, it can be burned through generators to create energy. “It’s a greenhouse gas that we’re using to create more energy rather than releasing it into the environment,” he said.

The generators, or methane engines, are “each as big as a truck,” Symmonds said. They work a lot like truck engines, but “instead of running off diesel, they run off of methane.”

Green energy on the horizon

City officials are eager to expedite greater reductions of the city’s dependence on non-renewable energy. That’s why Symmonds said the city is seeking approval for a second landfill project, developing part of the landfill to be run as a bioreactor. According to Symmonds, the Columbia bioreactor would be the first in Missouri, and one of only 11 in the country.

A bioreactor accelerates the rate at which waste decomposes and produces methane, making more of the gas available for energy conversion. “The bioreactor is changing the method in which we landfill our material,” Wieman said.

Landfills typically handle trash using a “dry tomb” method, in which the intent is to keep all storm water and leachate, liquid that filters through solid waste, out of the landfill cell. In a bioreactor, though, the opposite happens, and water is injected to help the waste degrade faster.

Bioreactors “accelerate that process by about tenfold,” Wieman said. They also serve the landfill’s goal to “consume your airspace wisely,” he said, because the faster waste decomposes, the faster it frees up space. The bioreactor could add five years to the life of the landfill. “What would take 50 to 100 years, we can do in two to 10,” he said.

The city must address concerns like odor control and possible shifts of decomposing material to obtain the Department of Natural Resources’ approval for operating the bioreactor. But if the department gives the go-ahead in 2008 as anticipated, Symmonds said, the bioreactor could be operating by 2009.

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