Researchers help expand gas project’s power

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To make gas, just add water.

Denton powers about 1,600 homes with methane captured from the city landfill — gas created after the city started adding water to the pile in 2008. Researchers at the University of Texas at Arlington are helping to double that power-generating capacity.

The project is the first of its kind in Texas, according to UTA’s lead researcher, Sahadat Hossain.

Landfills typically are kept covered and dry in order to limit methane emissions, said Hossain, an associate professor of civil engineering and internationally renowned expert on landfill management.

When a landfill is kept dry, natural decay occurs much more slowly, Hossain said. With the right amount of moisture and the right system to capture the methane, decaying organic matter can create enough gas to run a power plant.

Several such plants are running in Florida and other states, Hossain said.

Through April 2012, Hossain and his students studied an imaging system that allowed them to measure moisture in the Denton landfill without having to drill monitoring wells, which can allow methane to escape. Scientists have learned in early attempts of this work that the water doesn’t always percolate evenly through the pile.

“They made a swimming pool in a landfill,” Hossain said.

The Denton study allowed UTA researchers to create a new model that helps crews know when, where and how to water the pile in order to make the most gas.

The city paid the UTA researchers about $182,000 for the work. This year, the city agreed to another three-year grant, this one for $344,414, to pay for Hossain and Melanie Sattler, also a civil engineering professor at UTA, to study fugitive emissions at the landfill.

Methane is a powerful greenhouse gas that contributes to climate change, Sattler said. In addition, municipal landfills are a significant source of methane emissions.

The first year of the emissions study, the group will be taking measurements where gas is escaping, Sattler said. In the second and third years of the study, they hope to field test some strategies to reduce escaping gas. The strategies should not only help lessen the impact on the atmosphere but also help the city capture more gas for the power plant, Sattler said.

Vance Kemler, director of the city’s solid waste division, said the power plant, operated by DTE Biomass Energy, is small and currently generating about a third of the capacity it is designed to generate.

“We maxed out the output of the current plant,” Kemler said. “But we need more gas in order to build a second [generating] unit.”

Long term, Kemler said he sees the power plant as part of many strategies that can help extend the life of the landfill.

Sattler said the project also could encourage other cities to consider doing the same.

“Some people are reluctant to look at the concept because it’s different and nontraditional,” Sattler said. “But it has a lot of research backing it up — just not in Texas.”

PEGGY HEINKEL-WOLFE can be reached at 940-566-6881. Her e-mail address is pheinkel-wolfe@dentonrc.com.


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