Processing Magazine

Scientist develops method for producing electricity from wastewater

March 1, 2013

Dealing with challenges of any kind often requires thinking outside the box. Such an approach can be very useful when trying to figure out ways to tackle the global issue of energy resources and sustainability. According to Bruce Logan of Penn State University, who specializes in water resources, innovative ideas are often initially rejected on the grounds of being impossible or too expensive to do. However, with the pressing problem of clean water shortage, particularly in certain areas, thinking outside the box is the best solution.

Speaking at the New Horizons in Science meeting in Raleigh, N.C., Logan pointed out that one billion people in the world have no adequate access to drinking water, while twice as many lack decent sanitation. Estimates show that by 2025 one in four people globally will live in areas with severe water shortage.

Meanwhile, in the United States, water infrastructure accounts for at least three to five percent of the entire amount of electricity generated, or about 20 to 30 gigawatts -- equal to the output of 20 nuclear power plants. In recent years, there has been an increase in the amount of energy required for the production of drinkable water and for treating wastewater because of the fact that modern technology utilized in the process consumes more energy, Logan pointed out.

However, what many people still do not see is that there is energy within wastewater itself, the expert said. It is estimated that U.S. wastewater from domestic use, food processing and animal waste alone contains about 17 gigawatts of energy. Wastewater treatment uses 10 to 20 gigawatts, or between 1.5 percent and five percent of all electricity production, Logan said, noting that this was also an estimate and may not be precise. What matters most, though, is the fact that there is significantly more energy in the wastewater than the energy it takes to treat it, thus making wastewater a major energy resource. Much of this resource is at present wasted, as wastewater is hardly ever treated with the intention of extracting energy, he added.

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Logan is currently researching the options for doing this more efficiently. He believes that it can be achieved with the use of two types of microbes: exoelectrogens, which produce electric current, and electrotrophs, which consume electrons and produce hydrogen and methane. For his research, Logan placed exoelectrogens in microbial fuel cells. This experiment contains no moving parts but only the bacteria already present in wastewater. They gather around an anode, oxidizing biomass in the wastewater, and produce an electric current to a cathode. The experiment provided enough energy to supply electricity to a fan.

What Logan and his colleagues are trying to do is harness the power of microbes, which, even without the help of chemical additives, can help solve the resource crisis if these tests can be scaled up to real-world capacities. When this is achieved, wastewater treatment facilities could be self-sufficient and may even contribute energy to the grid, rather than consume electricity to function.