Cellulose is not digestible by humans, that's why it's considered dietary fiber. Plants produce it to use as their cell walls and to provide rigidity to their structure. Along with lignin and hemicellulose, cellulose makes up a large amount 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 but most vertebrates derive little nutrition from it.
Penn State researchers now say careful pairing of bacteria can create a fuel cell that consumes cellulose and produces electricity.
"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.
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.
The U.S. Department of Agriculture supported this work.
Source: Penn State
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Most Idiotic Rejection Of Course From Philosopher Of Science Not Grasping Relativity
- Lettuces Now, What Next - Could Astronauts Get All Their Oxygen And Food From Algae Or Plants?
- College Students Know E-cigarettes Aren't Tobacco, Their Professors Are More Confused
- Artificial Intelligence: It's Time To Talk About What Emotions We Want AI To Have
- Innate GMO Potato Deregulated By USDA
- An Historical Moment For Diabetes
- An Argument For Legalizing Doping In Sports
- "This is just warmed-over socialism and amateur Malthusian rhetoric - we have to cull the herd,..."
- "This professor is not confused. Ecigs are no more a tobacco product than Mountain Dew is a coffee..."
- "There is no shortage of technology to 'feed the world' but Fedoroff's techno-optimist fantasy illogically..."
- "The FDA can not approve needed drugs and approves un-needed drugs. One more argument that drug..."
- "Just adding a thought here. This is to do with the idea of adapting BIOS-3 and also crop growing..."
- Fish oil diet versus gut microbes
- Naps linked to reduced blood pressure and fewer medications
- Why girls are less interested in computer science: Classrooms are too 'geeky'
- Frogs make irrational choices - and what means for understanding animal mating
- Depression, blood pressure extremes predict highest rates of vascular events