RESEARCHERS STUDY WHY WASTE IN BIOREATCTOR LANDFILLS DEGRADES IN HASTE

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RESEARCHERS STUDY WHY WASTE IN BIOREATCTOR LANDFILLS DEGRADES IN HASTE
31 August 2003 - University of Wisconsin-Madison

It's not that the University of Wisconsin-Madison professor of civil and environmental engineering is excessively messy. Rather, he's studying bioreactor landfills, a relatively recent technology in solid-waste management that may help landfill owners make better use of their land-and of the waste itself.

Traditional landfills incorporate systems to collect leachate and limit waste exposure to liquids like rain. However, bioreactor landfills, which have emerged over the past decade, are designed to recirculate liquids such as rainwater or leachate through the waste to break it down more efficiently. "Rather than sending the leachate-the contaminated liquid-off site to be treated at a plant, we just pipe it back up and send it through the waste to help the degradation process," says Benson.

He and Morton Barlaz, a professor of civil and environmental engineering at North Carolina State University, are developing computer-based tools that will help predict bioreactor landfill behavior. Their comprehensive research project combines their expertise in solid-waste containment, hydrology and decomposition.

Thanks to advances like improved liners and barrier systems for traditional landfills, bioreactor landfill managers can operate their sites without worrying that the liquid will leak and contaminate groundwater. "Things that go in a landfill stay in there," says Benson. "So we can put liquids in confidently."

Because liquids enhance microbial processes that are key to waste degradation, one benefit to bioreactor landfill owners is increased "airspace," or volume, in the landfill. Since landfills close when the land and airspace are full, bioreactor landfill owners are able to squeeze more years of life out of their land.

Owners of traditional landfills pay to send their leachate to a water-treatment plant, while bioreactor landfill owners can avoid such costs. "As the system goes through its biochemical changes, it tends to lock up most of the contaminants, which is a real advantage," says Benson. "So you have a more sustainable management system. It's cleaning itself."

A number of demonstration bioreactor landfills exist in Canada and the United States. "There's a lot of interest in this nationwide in the solid-waste community because of the practical and economic advantages," he says. "This is something that a lot of people are trying."

Bioreactor landfills are relatively simple in concept; yet, it's difficult to predict their behavior-in part, because there are so many variables, says Benson. For example, the waste material itself is comprised of many materials. The biological processes that break down waste can vary. Thermal conditions within the landfill, as well as the amount, temperature and type of recirculated liquid, can change.

For their research, Benson and Barlaz each have established bioreactor landfills in their own laboratories. With industrial partners, they have installed sensors in several operating bioreactor landfills around the country and are monitoring their processes and conditions. Eventually, they will construct computer models to simulate those processes and conditions.

Their data and resulting predictive tools could help state and federal agencies regulate and evaluate bioreactor landfills. They also may help waste management companies make decisions about locating and operating new landfills.

A three-year, $750,000 National Science Foundation Partnerships for Innovation grant is funding the project.

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About: University of Wisconsin-Madison
In achievement and prestige, the University of Wisconsin-Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW-Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Many of its programs are hailed as world leaders in instruction, research and public service.

The university traces its roots to a clause in the Wisconsin Constitution, which decreed that the state should have a prominent public university. In 1848, Nelson Dewey, Wisconsin’s first governor, signed the act that formally created the university, and its first class, with 17 students, met in a Madison school building on February 5, 1849.

From those humble beginnings, the university has grown into a large, diverse community, with about 40,000 students enrolled each year. These students represent every state in the nation, as well as countries from around the globe, making for a truly international population.

UW-Madison is the oldest and largest campus in the University of Wisconsin System, a statewide network of 13 comprehensive universities, 13 freshman-sophomore transfer colleges and an extension service. One of two doctorate-granting universities in the system, UW-Madison’s specific mission is to provide "a learning environment in which faculty, staff and students can discover, examine critically, preserve and transmit the knowledge, wisdom and values that will help insure the survival of this and future generations and improve the quality of life for all."

The university achieves these ends through innovative programs of research, teaching and public service. Throughout its history, UW-Madison has sought to bring the power of learning into the daily lives of its students through innovations such as residential learning communities and service-learning opportunities. Students also participate freely in research, which has led to life-improving inventions from more fuel-efficient engines to cutting-edge genetic therapies.

Students, faculty and staff are motivated by a tradition known as the "Wisconsin Idea," described by UW President Charles Van Hise in 1904 as the compelling need to carry "the beneficent influence of the university ... to every home in the state." The Wisconsin Idea permeates the university’s work and helps forge close working relationships among university faculty and students and the state’s industries and government.

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