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April 30, 2004
Building a Better Landfill

After filling three 55-gallon fish tanks with garbage and watching — and smelling — the trash decay for months, Sharon Borglin knows a thing or two about landfills. And after winning a 2002 Department of Energy Outstanding Mentor Award, she also knows what it takes to ensure the next generation of scientists will also study sustainable living.

Sharon Borglin and her student Naomi Ndavu study microbial communities that live in landfills. (Photo Roy Kaltschmidt)

Over the past few years, Borglin, a staff scientist in Berkeley Lab's Earth Sciences Division (ESD), has contributed to research concerning landfill management; bacteria that eat hazardous metals; and how man-made endocrine disruptor pollutants enter the ecosystem. Along the way, she's mentored two college students for several semesters, one of whom has gone on to research wind energy in Southern California.

The fish tanks were part of a project completed last year in which Borglin and colleagues designed and built bioreactors for the study of aerobic and anaerobic landfill processes. Their goal was to learn how today's landfills, which encapsulate trash in nearly water- and air-tight liners, can be reworked to allow garbage to decay more rapidly.

"Today's landfills are like placing trash in a Tupperware container, where it slowly degrades over a hundred years," Borglin says. "In fact, core samples taken at landfills have yielded legible newspapers and intact bananas from 50 years back."

These dry tombs, as the landfills are sometimes called, date back to the 1970s when the Environmental Protection Agency enacted laws to curb harmful runoff. Although sealing landfills prevents harmful pollutants from escaping, it also stymies degradation.

When garbage like this is sealed in water- and air-tight cells, harmful runoff is reduced — but the garbage itself may not degrade for a long, long time.

Now, researchers are learning how to transform landfills from waste preservation systems into bioreactors. In these systems, bacteria — fueled by an influx of air and water — decompose the garbage. To learn more about they work, Borglin and colleagues developed three lab-scale bioreactors.

"We filled the fish tanks with actual trash brought in from home by ESD volunteers and supplemented it with paper, glass, cans, and leftover food from the cafeteria," Borglin says. "It sounds silly, but we created garbage."

In one of the garbage-filled fish tanks they added water, in another they added air and water, and in the third they added nothing. This mimics the different types of bioreactors used in the field: one kind uses only water, which produces methane. Another kind uses air and water, which degrades the garbage more quickly. Then, over 10 months, they monitored the rate at which the garbage settled in each tank, an indication of decomposition. Results of their project will be published soon.

"This work could help develop sustainable landfills," says Borglin. "A lot of landfills today are closed once they are full, and the land can't be used anymore."

In addition to landfill research, Borglin is working on a multi-institutional project for the Department of Energy's Genomes to Life program that's examining how certain environmental stresses affect the ability of bacteria to reduce uranium in the environment. This work, headed by Adam Arkin and Terry Hazen of the Virtual Institute for Microbial Stress and Survival, based at Berkeley Lab, includes studying how anaerobic bacteria react to stresses such as oxygen, and how this affects their ability to reduce uranium and other metals in the environment.

She's also examining the fate and transport of certain compounds called endocrine disruptors, which are sometimes released from wastewater treatment plants and enter the ecosystem, possibly affecting the life cycle of fish. In all these ways, Borglin is learning how to better manage the stuff we throw away, and make sure our garbage doesn't harm the environment.

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