Methane, often used for cooking and heating, is a potent greenhouse gas -- more than 20 times more effective at trapping atmospheric heat than carbon dioxide. A major source of slow methane leaks is old, abandoned landfills and town dumps.
While containing gas at these sites can be expensive, University of Illinois at Chicago researchers believe an effective and cheap way to trap it may be as easy as laying down a covering using charcoal as the key ingredient.
UIC civil and materials engineering professor Krishna Reddy and earth and environmental sciences research professor Jean Bogner think layers of biochar, either by itself or mixed with soil, can trap and hold on to escaping methane long enough for methanotropic bacteria to break it up, producing less-harmful carbon dioxide as a byproduct.
"Our concept is to design a cheap and effective cover system," said Reddy, who has done extensive research on landfill management solutions. "We've done preliminary studies on biochar and found it has the characteristic of being able to adsorb methane."
Biochar is charcoal made from biomass, such as wood and crop waste. It is basically carbon with high surface areas where bacteria cling, waiting to trap and consume any passing methane gas. Most methane escapes from old dumps or landfills before the bacteria can do its work. Biochar helps hold the gas in place.
Reddy and Bogner received a $350,000 research grant from the National Science Foundation to test biochar for use on landfills. The U.S. Environmental Protection Agency estimates there are at least 10,000 old or abandoned dumps and landfills around the country that could use an inexpensive containment cover to trap slow leaks of methane.
Reddy and Bogner will do lab analysis of biochar made from different sources, testing for ability to hold moisture, acidity levels, and ash content. They will determine which charcoals work best at containing methane, how well it works in soil mixes, and what thickness is needed to be effective.
Reddy said another advantage of biochar is that it helps oxygenate soil, providing an environment where methanotropic bacteria can flourish. It is a cheap, sustainable product that can be made from crop waste in a pyrolysis unit on site at a landfill. The process also produces a bio-gas or oil byproduct that can be used for fuel.
"Our lab data will be fed into a mathematical model that we'll use to scale up systems," Reddy said. "We'll do field testing to validate the model." The UIC project will take about three years.
"We want our model to serve as a design tool," Reddy said. "Every landfill site is different, but we hope our model can be used to analyze site-specific conditions to design an effective cover system."
"It's relatively cheap and it's a simple operation. We hope landfill operators and government regulators will like it," he said.
The NSF grant will support one undergraduate and two graduate student research assistants. Reddy also plans to discuss his research in graduate-level seminars, and in talks to government regulators and to middle- and high-school science teachers.
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