AMHERST, Mass., Jan. 17 (UPI) -- Batteries made with bacteria may in the future generate electricity from ocean mud while cleaning up organic pollution at the same time, researchers say in the journal Science.
"You could turn any type of waste organic matter into useful energy, if you can get the efficiency high enough," said researcher Derek Lovley, a microbiologist at the University of Massachusetts in Amherst. "The idea of harvesting energy from material that basically does not have any practical use is just an exciting possibility."
The organic chemicals in ocean mud represent a potentially vast source of energy. While humanity already taps into some of this fuel in the form of petroleum, most of this energy reservoir remains beyond reach because it is not nearly as easy to extract and use as oil.
The scientists discovered common, non-toxic microbes called geobacters have the power to harvest electricity from ocean mud. Since organic sediments are so abundant, "theoretically they could be an inexhaustible source" of fuel, Lovley noted in Science.
In addition, these bacteria do more than just eat up biological compounds found naturally in soil -- they can get rid of organic contaminants as well, "such as aromatic hydrocarbons," Lovley explained. "That's really important in cleaning up petroleum contamination of groundwater or contamination of water by landfills."
The researchers made mud-water batteries in fishtanks in collaboration with scientists at the Naval Research Laboratory in Washington. The batteries each had two graphite electrodes, one stuck in oxygen-poor mud loaded with bacteria and the other placed in the overlying water. The geobacters congregated around the electrode in the mud and consumed organic matter in the soil to gain energy.
As a side effect, the microbes generated a current through the mud-water battery. By transferring electrons onto iron oxides found naturally in the soil, they used iron oxides the same way humans use oxygen to get energy.
Microbiologist Caroline Harwood, of the University of Iowa in Iowa City, found these new batteries very interesting.
"I think they're an intriguing concept for augmenting the tools that we have to deal with the world's energy problems," Harwood said.
At their current level, the batteries can only power electronic devices with very low energy requirements, such as calculators and tiny light bulbs. In the short term, the researchers hope to power monitoring devices deep in the ocean with them, to alleviate the need to go back and change batteries.
"In the long term, we're trying to optimize the electron transfer from the bacteria to the electrodes to harvest more electricity from waste organic matter," Lovley said in an interview with United Press International. "Basically what's done now is people convert waste to methane gas to power sludge treatment plants. Our goal would be to help people go from harvesting energy as methane, which you have to burn, to harvesting energy directly as electricity."
A more immediate application than industrial power generation would be pollution cleanup. The very presence of the electrodes stimulates the geobacters naturally present in the soil, enhancing their ability to degrade contaminants.
"It's incredible -- they go from almost undetectable to being the dominant member of the microbial community," Lovley said.
Microbiologist Greg Zeikus at Michigan State University in East Lansing found these new findings very exciting.
"This work has come closer to developing accessible marine batteries as a way to meet our electricity needs," he noted in Science.
(UPI photo is available: No. WAX2002011797)
(Reported by Charles Choi in New York.)
