by Amos Esty
Illustrations by Jim Paillot
In this issue:Trash Power
Jenna Jambeck has a passion for waste management, which helps to explain why she smiles when she admits that she has been called "the garbage queen." It's not that she likes trash itself, of course. But she does enjoy the challenge of figuring out what to do with the immense amount of waste produced in the United States—about 251 million tons in 2006.
"Part of the problem is that it just gets put on the curb and taken away," says Jambeck, a research assistant professor of civil and environmental engineering. "It's nice that it gets taken away, but people usually don't want to know where it goes." Some trash is recycled, but most—about 55 percent—ends up in landfills.
One of Jambeck's current projects involves producing electricity from landfill wastewater called leachate. She compares the way leachate forms to brewing coffee. As rainwater percolates through a landfill, it picks up contaminates. So, before the leachate can build up, it is pumped out for treatment.
Some of the contaminants that make leachate a health hazard also make it a potentially rich source of energy. Jambeck and graduate student Lisa Damiano '07 are experimenting with using microbial fuel cells, devices similar to common batteries, to produce electricity from leachate.
Their research grew out of an award-winning undergraduate environmental-design competition that several UNH students, including Damiano, entered in 2007. The team developed an MFC that used cow manure to generate electricity. The design inspired Jambeck, one of the team's advisers, to think about using leachate as a raw material. She asked Damiano to run leachate through the MFC to see what happened. When the experiment produced electricity, they used their data to win funding to continue the project.
Their current model consists of a small, cubical Plexiglas chamber that holds both the leachate and two electrodes. Bacteria break down the organic matter in the leachate, and some bacteria are then able to transfer an electron outside their cell wall. The result is a flow of electrons between the electrodes in a process known as electrogenesis. But the electricity produced is really only a byproduct, however valuable—the most important result is that the process reduces the amount of organic matter.
Jambeck thinks eventually a landfill could pump leachate directly into an MFC, which would both treat the wastewater and produce enough electricity to help power the facility's operations.
So far, MFC models have not generated enough electricity to make them cost-effective on a large scale, but Jambeck and Damiano are currently working on developing a more efficient model. The next step will be to develop a larger, pilot-scale model.
Landfills produce a lot of leachate, so this research could be of interest to the waste management industry. For example, the Turnkey landfill in nearby Rochester, N.H., produces about 70,000 gallons every day.
Ultimately, Jambeck would like to see Americans produce a lot less trash. Until that happens, she'll try to make sure that our garbage doesn't go entirely to waste.
In early fall 2006, three people died and nearly 200 became ill after eating spinach tainted with E. coli. A year later, another outbreak forced a New Jersey company to recall more than 20 million pounds of ground beef.
These cases made headlines for weeks, but they were only a fraction of the 325,000 hospitalizations and 5,000 deaths caused by food-borne pathogens every year in the United States. Aaron Margolin, professor and chair of the UNH microbiology department, is among those working to reduce these numbers.
Margolin is not particularly surprised when outbreaks occur. As part of one public-health class, he had his students test a package of alfalfa sprouts for contamination. The class found traces of both E. coli and salmonella. "It even said on the package 'triple tested,'" says Margolin. Of course, he notes, "it didn't say why it was triple tested or what the results were."
Margolin serves as an adviser to the Food and Drug Administration, which has given him insight into the difficulties involved in food safety. The FDA and the U.S. Department of Agriculture share responsibility for regulating food products, and who governs what can at times seem arbitrary. For example, the FDA has jurisdiction over milk, but the USDA oversees beef. The task became even more complicated after 9/11, when the FDA turned more of its attention to preventing bioterrorism.
At ﬁrst, says Margolin, government agencies paid attention to produce and bottled water. As part of that effort, Margolin develops techniques and protocols that will enable the FDA to detect food-borne pathogens as quickly as possible, whether they are the result of bioterrorism or accidental contamination. For security reasons, Margolin can't name the pathogens he investigates, but he does say that they have been identified by the FDA as "potential bioterrorist agents."
One increasingly difficult challenge is the globalization of the food supply, and not every country meets standards that would be considered acceptable in the United States.
The traditional method of detecting food-borne pathogens is to grow the organism until it can be identified. That can take time, from as little as a day to more than a week. Margolin points out that for some food items, such as lettuce, waiting a week would mean that much of the lettuce would be beyond its shelf life.
So Margolin is helping to develop faster methods of detection. The primary technique he uses is called polymerase chain reaction, which amplifies a sequence of a pathogen's DNA to make it identifiable in as little as a few hours.
Even with PCR, however, the process of detecting pathogens isn't easy. One difficulty is deciding exactly what to look for. "If you're looking for the wrong piece of nucleic acid, the organism could be there, but you may not find it," says Margolin. Another problem is that the more complex the food, the more difficult it is to find a pathogen.
Margolin remains skeptical that consumers can avoid all sources of potential contamination, but he does think that progress has been made. When he started his work on pathogens, the only method of detection was the time-consuming process of growing the organism. Now, some organisms can be detected in a matter of hours. "To us, that's a heck of an accomplishment," he says.
There's a reason New England is known as the nation's tailpipe. Mercury, sulfur and other contaminants emitted by distant power plants are carried here by prevailing winds. But according to members of the Climate Change Research Center at UNH, residents of New England might be guilty of a similar offense.
In 2004, Barkley Sive, research associate professor of atmospheric chemistry, led an effort to measure the amount of volatile organic compounds—a category of gases that can cause air quality and health problems—in New Hampshire's air. The study, supported by AIRMAP, a UNH air quality and climate program, was part of an international effort to find out more about the long-range transport of pollution. Sive analyzed air samples from Thompson Farm, just south of the university. The study yielded some surprising results, he says: "unusually high propane levels."
To find out if the high levels were an isolated event or applicable to the region as a whole, UNH graduate student Marguerite White '03 conducted surveys of propane levels in northern New England. She and several other researchers drove loops, each about 250 to 300 miles long, taking air samples along the way. They avoided areas downwind of traffic congestion or construction sites, which could have skewed the results, and they took samples in every season and at a variety of elevations.
White's work confirmed that there is, indeed, a lot of propane in the skies across northern New England. And she and Sive think they know the cause—leakage from liquefied petroleum gas tanks. Propane is a major component of LPG, which is widely used in New England for heating as well as for powering gas grills.
Previously, it was assumed that vehicle exhaust and fires were the primary sources of ambient propane. But when White and Sive took air samples near LPG reﬁlling stations, they found high levels of propane and a close match to the ratio of propane to other compounds present in LPG. Sive calls that piece of evidence "the smoking gun." The results did not prove that LPG leakage alone is to blame, but it was a significant and unexpected contributor.
The amount of propane emitted by each tank is miniscule, but it adds up quickly. Sive and White estimate that every day about 80 tons of the gas are leaked—about the same as the amount emitted in urban areas such as Mexico City and Santiago, Chile.
Propane can react with other gases, such as nitrous oxides, to create ozone, which is one of the major components of smog. High ozone levels can aggravate asthma and increase the risk of respiratory disease.
Unlike New England, Mexico City and Santiago are located in valleys that trap pollutants. Because of New England's geography and the fact that propane is a long-lived compound, much of it will carry downwind—all the way across the Atlantic. "What we measure here is transported to Europe," says Sive. In other words, when it comes to propane, Europe is New England's tailpipe.blog comments powered by Disqus