Bacteria make clean power

Researchers have previously shown that is possible to build a fuel cell run by microbes.

Pennsylvania State University scientists have done them one better. The Penn State researchers' microbial fuel cell is fueled by wastewater skimmed from the settling pond of a treatment plant, and the process of drawing electricity from the microbial action taking place in the wastewater also cleans the water.

The researchers' prototype produced as much as 50 milliwatts of power per square meter of electrode surface. Fifty milliwatts is about five percent of the electricity need to light a mini Christmas tree light. At the same time, the process removed as much as 78 percent of the organic matter in the wastewater, according to the researchers. The device handles wastewater that contains particulate material.

The device runs using bacteria that are naturally present in the wastewater. As the bacteria break down wastewater materials they pass electrons to the fuel cell's negative electrode. This pumps the electrons through a wire to form a useful current. The electrons return through the cell's positive electrode and combine with hydrogen ions and oxygen to form water.

An economical prototype of the microbial fuel cell could be produced in five years, and a practical commercial device within ten years, according to the researchers. The work is slated to appear in Environmental Science and Technology.