Microbial Fuel Cells Promise Power from Sludge

A microbial fuel cell technology developed at Oregon State University (OSU) promises to produce 10 to 50 times more electricity per volume directly from wastewater than most other approaches using microbial fuel cells. The breakthrough could reportedly have significant implications for waste treatment plants by replacing the “activated sludge” process that has been widely used for almost a century. The new approach could produce significant amounts of electricity while effectively cleaning the wastewater, OSU researchers say.

5. The glimmer of sludge. Advances in microbial fuel cell technology used to clean sewage could allow waste treatment plants to produce much more electricity than previously estimated, research by Oregon State University (OSU) shows. Here, Hong Liu, an associate professor in the OSU Department of Biological and Ecological Engineering, holds up a research fuel cell. Courtesy: OSU

This technology cleans sewage via a different approach than the aerobic bacteria used in the past. Bacteria oxidize the organic matter and, in the process, produce electrons that run from the anode to the cathode within the fuel cell, creating an electrical current (Figure 5). “Almost any type of organic waste material can be used to produce electricity,” OSU researchers said, “not just wastewater, but also grass straw, animal waste, and byproducts from such operations as the wine, beer or dairy industries.”

The findings, published in the journal Energy and Environmental Science, note that major advances in the technology have been made since its potential was first reported several years ago. New concepts—reduced anode-cathode spacing, evolved microbes, and new separator materials—could allow it to theoretically produce more than 2 kW per cubic meter of liquid reactor volume.

The OSU system is now seeking funding for a pilot study at a site, such as a food processing plant, that is a contained system that produces a steady supply of certain types of wastewater and could provide significant amounts of electricity. Research is ongoing on optimizing the use of necessary microbes, reducing material costs, and improving function of the technology at commercial scales, OSU scientists said.

Once advances are made to reduce high initial costs, researchers estimate that the capital construction costs of this new technology should be comparable to those of the activated sludge systems in use today—“and even less expensive when future sales of excess electricity are factored in,” they said. The approach is expected to have specific value for developing nations, where access to power is limited and sewage treatment at remote sites is difficult as a result.

—Sonal Patel is POWER’s senior writer.