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UD team develops high-tech landfills

Paul Imhoff, associate professor of civil and environmental engineering

NEWARK, DE.--With increased attention on methane as an important contributor to global climate change, a University of Delaware research team has been awarded nearly $600,000 as part of a U.S. Department of Energy research and development initiative to bring improved engineering and technology to the nation’s landfills, which produce significant quantities of the greenhouse gases.

Methane is of concern because it is more than 20 times more effective in trapping heat in the atmosphere than carbon dioxide over a 100-year period. Methane also is of interest because it is an important energy source.

As a result, efforts to either reduce methane emissions or to put them to more effective use can provide considerable environmental and economic benefits.

The UD research team is led by Paul T. Imhoff, associate professor of civil and environmental engineering, and includes Pei C. Chiu, associate professor of civil and environmental engineering. The team is working with three partners--the Yolo County (Calif.) Planning and Public Works Department, the nonprofit Institute for Environmental Management based in Palo Alto, Calif., and the firm Hydro Geo Chem Inc., of Tucson, Ariz.

Imhoff said the Yolo County government “is innovative in its approach to solid waste management,” constructing several well-instrumented bioreactor test cells to generate and collect methane. Bioreactor landfills feature the controlling and optimizing of biological conditions in the waste to allow for more rapid and complete decomposition.

Because of concerns about escaping methane, Imhoff said most modern landfills are controlled, meaning there are mechanisms in place to collect the gas and either destroy it by “flaring it off” or use it to turn turbines to generate power. It is estimated that landfills produce more than 30 percent of the United States’ methane emissions created by human activity.

UD doctoral student Byunghyun Han collects data from the top of a landfill cell at the Delaware Central Solid Waste Management Center near Sandtown. The white pipes protruding from the grass cover are used to collect gas samples.

“Currently, the design for how that is done is somewhat simplistic,” Imhoff said. Conventional landfills using current technologies typically collect about 70 percent of the gases emitted, which means the remaining 30 percent is escaping to the atmosphere. The efficiency of gas collection is very dependent on the skill of landfill operators.

“We think we can do better if we engineer the entire gas collection process,” Imhoff said.

To do that, the UD research team is developing a “revolutionary approach” in the Intelligent Bioreactor Management Information System (IBM-IS) for the control of fugitive landfill gas emissions. The system is a computer-controlled program that manages a network of automated sensors and control points to manage and control landfill gas extraction and liquid addition.

Imhoff said the utility of the IBM-IS approach also will be evaluated for the control of landfills where the objective is to maximize biodegradation and minimize the formation of methane by controlled injection of air and liquids.

“Our goal is to optimize the systems to collect the gas and to generate the gas through the addition of water in these bioreactors,” Imhoff, who has a research interest in how fluids flow through different types of porous media, said.

Imhoff said the concept for methane-producing bioreactors has been around for about 20 years, with pioneering work conducted by the Delaware Solid Waste Authority. Until now, though, a combination of regulatory issues and economic factors inhibited their development. “Now, regulators and landfill owners can see an economic impact through the collection and use of methane, and they also see that there is an environmental benefit,” he said.

The federal grant will fund fieldwork, computer modeling and laboratory research, Imhoff said.

The grant is part of $62.4 million in “clean coal” research and development awards announced by Secretary of Energy Samuel Bodman. The primary focus of the project is to develop a coal-fire zero emissions power plant, although the initiative also provides for the advancement of other energy and climate goals.

Article by Neil Thomas
Photo by Kevin Quinlan