Tackling Waste Management Problems With Bacteria-Powered Fuel Cells

Bacteria-powered fuel cells created by a team of University of Southern California scientists have very practical, self-sustaining applications that can save some U.S. city services millions, Geobiologist Kenneth H. Nealson, the Wrigley Chair in Environmental Studies at USC, said at a meeting last week.

Nealson is working with the City of San Diego's Environmental Services Department, which is responsible for costly waste management services.

"We believe we can take their system and make it one-tenth the size," said Nealson. "That would save them on the order of $80 million a year."

Nealson said the waste could be cycled without creating any sewage sludge.

Although sludge can be "safely recycled and applied as fertilizer to sustainably improve and maintain productive soils and stimulate plant growth," according to the United States' Environmental Protection Agency, it cannot be deposited in landfills due to toxins like nitrogen and chromium. Besides chromium, a carcinogen and mutagen, sludge includes hazardous pharmaceuticals and various other toxins.

It makes sense, therefore, that there is much optimism surrounding Nealson's research. The program could be fully implemented within 10 to 15 years, according to a confident Nealson.

Although the microbe power cell research is promising, it can't solve huge problems.

"You're not going to power city hall with this thing," said Nealson, who expressed concerns that some of his colleagues have suggested their research will yield solutions to larger-scale problems. "It's not in the cards."

Shewanella, a marine bacterium at the core of the research, is able to modify metals by making them saturated with electrons, ultimately creating an electrical charge.

The microbial fuel cells create a current by using organic carbon, waste products, as an energy source. Oxygen is used as an electron acceptor, a compound that accepts a transferring of electrons from another compound.

Microbes use the anode, an electrode from which an electric current is able to flow, similarly to how they would use solid irons in nature.

The result of the process is less toxicity, as the bacterium clean up residue and keep metals, such as iron and aluminum, free of corrosion.

Nealson's research isn't new. It's been around since the 1990s. Many of his colleagues, however, were skeptical. The research challenged accepted modes of thinking about bacteria, namely that bacteria can mediate electron flow between layers. Or, as Nealson likes to put it, "communicate" between the layers.

"It's just now getting into the textbooks," said Nealson. "When people don't like something, even evidence is hard to convince them. But we all know that--it's true in every field."

Nealson said his colleagues felt that because they "didn't know about this" it meant it "didn't exist," insisting on dismissing the new science for several years rather than letting go of their dogmas.

"To do science right you need to do things in triplicate," Nealson said. Repeated experiments conducted independently proved that Nealson was right. Now that he's convinced his colleagues, at least most of them, Nealson and his team can recreate the experiment at higher power input levels to tackle small-scale problems.

Reut R. Cohen is a graduate student at the University of Southern California's Annenberg School for Communication & Journalism, which has partnered with KCET-TV to produce stories on Southern California.