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Bacteria From Wastewater Used To Power Microbial Fuel Cells

In between plexiglass plates two centimeters apart, an energy revolution is brewing. Or fermenting, to be more precise.

Those plexiglass plates hold a complex bacterial mixture derived from the dirty water that flows through sewers. By adding an anode and a cathode, researchers Yanzhen Fan, Hongqiang Hu, and Hong Liu of Oregon State University (OSU) in Corvallis, Ore. have created a rudimentary battery, a bacteria-powered energy generator known as a microbial fuel cell (MFC).

This revolutionary MFC, the size of a thick book, captures the metabolic energy of the bacteria to generate over 10 times more power than MFCs of similar structure and size. In a paper published September 27, 2007 in the Journal of Power Sources, assistant professor of bioenergy Hong Liu and her collaborators describe their new fuel cell and its increased power output. By including a cloth layer on the cathode, Liu's research group is able to reduce the internal resistance of the MFC and generate more power in a smaller space.

Demonstrating the potential to miniaturize this type of technology is an important breakthrough, according to Bruce Logan, professor of environmental engineering at Pennsylvania State University in University Park, Pennsylvania.

Logan, an expert in microbial fuel cells, notes that by adding the inexpensive cloth layer, Liu's group at OSU has made an MFC that can more efficiently generate power in a small space. For potential applications of MFCs such as cell phone chargers, he notes "you don't want something the size of a refrigerator. You want a small power source.” The new MFC can now generate enough power to run a small fan or a flashlight, with the promise of even greater energy output with further refinement of the fuel cell.

For Liu, microbial fuel cells are more than just a way to see if bacteria can power a flashlight. She hopes to use MFCs to combat rising energy demand, particularly in the realm of wastewater treatment. According to Liu, five percent of the electricity usage of the U.S. is dedicated to treating wastewater and purifying the water supply.

In the developing world, the need to improve water quality could put further demands on dwindling resources. Liu notes, "Ninety-five percent of sewage is without any treatment in developing countries.” Beginning to treat that sewage would require massive amounts of energy. A native of China, Liu notes that in her home country, "the water quality issue is much more serious than in the United States. I hope I can develop a product that can be used in this environment.”

Liu's goals are shared by her graduate student Hongqiang Hu. Like Liu, he hails from China and foresees use of their MFC to power wastewater treatment, both in the U.S. and also in rapidly industrializing nations like China. "By incorporating microbial fuel cells in water treatment facilities, the cost of operation could be reduced, and a dual objective of energy production and wastewater treatment can be achieved,” Hu asserts.

MFCs can also be used as a portable power source. Liu believes that agricultural environments are particularly well-suited for this type of technology. Farms are often in less accessible rural areas and generate waste products that could be utilized in MFCs. Agricultural byproducts such as cornstalks and manure could be used to feed the bacteria in the MFCs. By reclaiming these otherwise wasted products to run MFCs and generate power for small appliances, farmers could be more self-sufficient.

MFCs may be well-suited to power supplies or wastewater treatment, but "the energy produced by microbial fuel cells is still very low,” says Liu. "We need to further optimize the system to realizing its practical applications.” She envisions that the future of energy research will include many alternatives. For her part, Hong Liu will work to create better MFCs to fuel increasing energy demand.

Sara Selgrade is a graduate student in genome sciences at the University of Washington.

Image:

The new microbial fuel cell produced at Oregon State University can generate enough energy to power a small electronic device. Photo: Hong Liu


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