Biological engineers at Oregon State University have designed a microbial fuel cell that is capable of generating about 10 times more electricity than previously possible from an air cathode microbial fuel cell of the same size.

This design breakthrough could allow microbial fuel cells to be used more widely as sources of sustainable energy, said Hong Liu, an assistant professor in the OSU Department of Biological and Ecological Engineering.

The new design could ultimately lead to portable systems for power generation that are simultaneously capable of providing reusable water for developing nations and remote areas. The fuel cell design could also significantly reduce the amount of electricity used at large wastewater treatment facilities.

“We have successfully modified the fuel cell structure to enhance power generation,” said Liu, who co-authored the article with fellow OSU professor Yanzhen Fan and OSU graduate student Hongqiang Hu.

Microbial fuel cells, also known as biological fuel cells, use bacteria to convert biodegradable materials such as wastewater pollutants into electricity. As the bacteria consume the pollutants, they shed electrons, which flow through a circuit and generate electricity. In the process, pollutants are broken down, resulting in clean water.

Microbial fuel cells, especially those with air cathodes, hold great promise for many practical applications, due to their simple configuration and renewable and abundant fuel sources. However, the power outputs have historically been so low the devices have not been considered as viable sources of electricity.

The new design developed by the OSU researchers involves sandwiching a cloth layer between the anode and the cathode parts of the microbial fuel cell, a configuration that greatly reduces the internal resistance, resulting in a much higher power density, Liu says.

In lab experiments, Liu’s team successfully generated 1,010 watts per cubic meter of reactor, or enough to power 16 60-watt light bulbs. The highest previous level of sustainable electricity generated from a cubic meter of air cathode microbial fuel cell is less than 115 watts. In experiments done even more recently, Liu and colleagues have generated more than 1,500 watts from the same reactor volume.

The design improvements could eventually lead to a dramatic reduction in the cost of operating wastewater treatment plants in the United States and elsewhere.

Five percent of the electricity in the U.S. is used for water and wastewater treatment, mainly to power pumps and other equipment. “By incorporating microbial fuel cells in water treatment facilities, the cost of operation could be reduced,” Liu says.

Although scaling up microbial fuel cells to help power large wastewater facilities is a long-term goal of Liu’s, she says small scale systems will be feasible sooner. “It would be useful to build a smaller system for individual households. This is something the world can use very soon, especially in countries like China and India.”

While microbial fuel cells can't solve all global environmental and energy problems, they can help, Liu says.

“Our research results are very promising. There is a real future here, and I hope we can make a small contribution to the world.”

Liu’s research is supported in part by a $200,000 grant from the U.S. Department of Transportation through the Sun Grant Initiative, the OSU General Research Fund and the OSU Agricultural Research Foundation.