Two bacteria better than one in cellulose-fed fuel cellJuly 30, 2007No currently known bacteria that allow termites and cows to digest cellulose, can power a microbial fuel cell and those bacteria that can produce electrical current cannot eat cellulose. But careful pairing of bacteria can create a fuel cell that consumes cellulose and produces electricity, according to a team of Penn State researchers. "We have gotten microbial fuel cells to work with all kinds of biodegradable substances including glucose, wastewater and other organic wastes," says John M. Regan, assistant professor of environmental engineering. "But, cellulose is tricky. There is no known microbe that can degrade cellulose and reduce the anode. "We overcame this by putting together a microbe that can degrade and ferment cellulose and an anode-reducing bacterium that can live off the fermentation products," he says. Microbial fuel cells work through the action of bacteria that can pass electrons to an anode. The electrons flow from the anode through a wire to the cathode, producing an electric current. In the process, the bacteria consume organic matter in the water or sediment. Plants produce cellulose to use as their cell walls and to provide rigidity to their structure. Along with lignin and hemicellulose, they make up huge amounts of the biomass produced by plants. Some animals, ruminants and termites for example, can break down cellulose with the aid of bacteria that live in their digestive tract. Humans and most vertebrates derive little nutrition from cellulose. The researchers, who include Regan; Thomas E. Ward, research associate; and Zhiyong Ren, graduate student, looked at Clostridium cellulolyticum, a bacterium that ferments cellulose, and Geobacter sulfurreducens, an electroactive bacterium. Both are anaerobic, living in places where no free oxygen exists. This fermenter produces acetate, ethanol and hydrogen. The electroactive bacteria consumed some of the acetate and ethanol. They report the results of their study in a recent online issue of Environmental Science and Technology. "We thought that maybe we did not need a binary setup, maybe uncharacterized bacterial consortia would work" says Regan. "It worked, but not as well as the two specifically paired bacteria." One problem with anaerobic bacteria - and the reason the researchers looked into an uncharacterized mixture of bacteria - is that currently the most efficient microbial fuel cells use an air cathode. Unfortunately, it is impossible to have an air cathode without some oxygen leaking into the reaction chamber, killing strictly anaerobic bacteria and reducing output. "We tried an aerobic cathode with the binary culture and it will not work," says Regan. The researchers settled on a two-chamber fuel cell that produced a maximum of 150 milliwatts per square meter. "We achieved a low power density because of the two chamber system," says Regan. "Current fuel cell designs produce about ten times that." Currently the researchers are using pure, processed cellulose without any hemicellulose or lignin. They are just beginning to look at other cellulose products so the fuel cells can operate on less manufactured feedstock. As a proof of concept, the researchers are happy with their results, but they would like to see the power density increase. One approach would be to find a community of bacteria that could tolerate small amounts of oxygen because some of the bacteria use up the oxygen before it reached the anaerobic bacteria. Another approach would be to improve the design of the oxygenless fuel cell. Penn State |
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| Related Fuel Cell Current Events and Fuel Cell News Articles Toward home-brewed electricity with 'personalized solar energy' New scientific discoveries are moving society toward the era of "personalized solar energy," in which the focus of electricity production shifts from huge central generating stations to individuals in their own homes and communities. U of C chemists discover recipe to design a better type of fuel cell Fuel cells are often touted as one method to help decrease society's addiction to fossil fuels. But there is still a lot of work to be done before fuel cells will be ready for mass market to be used in transportation, home heating and portable power for emergencies. Ion Tiger fuel cell unmanned air vehicle completes 23-hour flight The Naval Research Laboratory's (NRL's) Ion Tiger, a hydrogen-powered fuel cell unmanned air vehicle (UAV), has flown 23 hours and 17 minutes, setting an unofficial flight endurance record for a fuel-cell powered flight. Smaller isn't always better: Catalyst simulations could lower fuel cell cost Imagine a car that runs on hydrogen from solar power and produces water instead of carbon emissions. While vehicles like this won't be on the market anytime soon, University of Wisconsin-Madison researchers are making incremental but important strides in the fuel cell technology that could make clean cars a reality. SRI to present hydrogen fuel safety research results at 2009 International Conference SRI International, an independent nonprofit research and development organization, announced today it will present new research identifying methods for designing safer structures in the future for hydrogen fueled vehicles, at the upcoming International Conference on Hydrogen Safety, Sept. 16 - 18, in Ajaccio-Corsica, France. Making more efficient fuel cells Bacteria that generate significant amounts of electricity could be used in microbial fuel cells to provide power in remote environments or to convert waste to electricity. Hydrogen Storage Gets New Hope A new method for "recycling" hydrogen-containing fuel materials could open the door to economically viable hydrogen-based vehicles. Growth Spurts: Berkeley Lab Researchers Record First Real-Time Direct Observations of Nanocrystal Growth in Solution The veil is being lifted from the once unseen world of molecular activity. Not so long ago only the final products were visible and scientists were forced to gauge the processes behind those products by ensemble averages of many molecules. Wastewater produces electricity and desalinates water A process that cleans wastewater and generates electricity can also remove 90 percent of salt from brackish water or seawater, according to an international team of researchers from China and the U.S. NRL's XFC UAS achieves flight endurance milestone The Naval Research Laboratory (NRL) has completed a successful flight test of the fuel cell powered XFC (eXperimental Fuel Cell) unmanned aerial system (UAS). More Fuel Cell Current Events and Fuel Cell News Articles |
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