By Melissa Reynolds

Garbage may be thought of as the last resort when looking for alternative sources of energy, but a new experiment may prove that wrong.

The microbial fuel cell (MFC) creates energy much like a hydrogen fuel cell, but it runs off wastewater. In the process, sewage-eating bacteria create a chemical reaction which generates the renewable energy, and purifies the water. In the end, you have not only converted waste into electricity or hydrogen, but also end up with clean water in the process. "It (the microbial fuel cell) generates electricity from organic matter," says Kappe Professor of Environmental Engineering Bruce Logan from Pennsylvania State University who, along with some colleagues, has constructed the MFC.

The MFC works by placing bacteria in the anode chamber of a specially-designed fuel cell that is free of oxygen, then attaching it to an electrode. The electrons obtained from oxidation are then transferred to the electrode. In the MFC, the electrons go to the anode while the counter electrode (the anode) is exposed to oxygen. The electrons, oxygen and protons combine to form only water.

"If you could treat water, you could save a lot of money," Logan says of the uses of the MFC. The MFC helps meet the need for a renewable and clean source of energy, as well as meet the need that 2 billion of the worlds people have for adequate sanitation, through its treatment of waste water.

The cells, which are about the size of a beer can, can power various smaller devices including a small fan. If made on a bigger scale, however, a larger MFC could work as a small sewage treatment plant, which would be beneficial for developing countries where electricity, such as that to run a treatment plant, can be in short supply.

The power that the MFC could generate is beneficial with many people consuming more and more energy each year. In the US, 5 percent of electricity produced is used for the waste and wastewater infrastructure with 1.5 percent used for wastewater treatment. By treating the sewage of 100,000 people, up to 2.3 megawatts of continuous power could be generated, enough to supply electricity for 1,500 homes.

While the MFC has not been commercially used yet, Logan is certain of what he wishes for the future. "We hope that one day it becomes a source of renewable energy," Logan says.