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01-18-06
By David Stauth, 541-737-0787
Source: Hong Liu, 541-737-6309
CORVALLIS, Ore. - New "microbial fuel cell" technology being developed at Oregon State University could revolutionize the treatment of wastewater, using organic material that until now has literally been wasted and creating either usable electricity or hydrogen to help run the cars of the future.
Some of the latest findings on these systems were recently published in a professional journal, Environmental Science and Technology, by engineers from OSU and Penn State University.
With slight adaptations, these systems could take almost any biodegradeable organic matter and produce a useful product - such as the electricity to help operate a waste treatment plant or hydrogen for fuel cells, which many experts believe will be the most practical alternative to gasoline-powered vehicles.
When used with sewage, another fringe benefit of the process is that it also cleans the water by a completely different method than the traditional use of aerobic bacteria, opening the door for new generations of waste treatment plants that are efficient, effective and might produce much of the energy needed for their own operation.
"These systems would use oxidation to remove up to 80 percent of the pollutants in wastewater, and at the same time provide a substantial portion of the energy used to operate the treatment plants," said Hong Liu, an assistant professor of biological and ecological engineering in the OSU College of Engineering. "In the United States, about $25 billion a year is spent for domestic wastewater treatment, so major cost savings may be possible.
"And in developing nations where waste treatment technologies are often considered too expensive, making a waste treatment plant almost self-sufficient in energy might mean the difference between being able to afford proper treatment of wastes, compared to no treatment at all."
Those possibilities, Liu said, will take further refinement of existing technology. But the concept has clearly been proven in laboratory experiments, she said. It's renewable, and efforts are under way to bring down costs, identify less expensive materials and improve operational efficiency.
It's been known that microbial fuel cells can be run from high-energy materials such as glucose, but is now clear that many organic waste materials may also work, including grass straw, wood pulp, and of course wastewater. Bacteria oxidize the organic matters and, in the process, produce electrons that travel from the anode to the cathode within the fuel cell, creating an electrical current.
As a new concept in sewage treatment, this approach eliminates the need to pump oxygen into a mixture of sewage and aerobic bacteria - in one stroke eliminating almost half of the cost associated with a conventional sewage treatment plant.
For hydrogen production, some of the latest studies outline a related process in the absence of oxygen that uses an electrical assist to greatly increase the efficiency of direct hydrogen production at the cathode of the reactor. This "bio-electrochemically assisted microbial reactor" also treats the wastewater at the same time - just like in the approach used to create electricity - but instead yields hydrogen as a useful end product and the ultimate power source for hydrogen fuel cells. And the approach is more cost-effective than existing technology to produce hydrogen, which uses large amounts of electricity.
"Some of the newest experiments indicate that for hydrogen production, we can increase the amount of potential hydrogen recovered from sewage from about 15 percent to about 70 percent," Liu said. "This completely anaerobic technology is very promising, but we still have improvements to make."
Part of the challenge, scientists say, will be to identify less costly materials that produce results similar to those already being achieved in laboratories with fairly expensive materials, such as platinum.
Depending on the level of improved efficiencies and other improvements, researchers believe it may be possible to create sewage treatment plants that are completely self-sufficient in energy production. Alternatively, if there is more of a demand for hydrogen to use in fuel cells and the next generation of automobiles, the technology could be aimed in that direction. But in either case, what's now considered wastewater would become a valuable energy resource - not a waste.
In other work that's under way at OSU, oceanographers are using related processes to harness plankton in the ocean as a fuel source, creating mobile instruments that might glide through the water, producing their own energy as they go, and aid oceanographic research. And other devices might have value to provide energy in remote areas where organic materials are available but electrical grids are not.
The theoretical ability of microbes to produce electricity has been known for decades, scientists say, but only in the past few years has the efficiency of these devices been improved enough to make them useful for various purposes.
Some of the most recent research in this field has been funded by the U.S. Department of Energy and the National Science Foundation.
"Bacteria eat food to get energy, just like people do," Liu said. "But in the process they shed electrons, and this is something we're learning how to use. The concept is very environmentally safe and should find some important applications."
About the OSU College of Engineering: With the nation's fourth highest percentage of women faculty and the 22nd largest undergraduate enrollment, the OSU College of Engineering emphasizes highly collaborative research to solve global problems, and offers innovative Platforms for Learning® to enhance hands-on teaching and develop work-ready graduates.