In the late 19th century, gaslights used gas collected from rotting sewage. Believe it or not, technology has come full circle, and it is once again possible to gain energy, this time electricity, from sewage. We don’t have to give up our modern wastewater treatment plants and return to unsanitary conditions to do it, either. All we need to do is take full advantage of the recently invented microbial fuel cell.
Wastewater is full of germs, which feast on the nutrients it contains. Their activity is part of what makes modern wastewater treatment plants work. In the process, they give off methane. It has long been possible to extract that methane using anaerobic digesters and burn it. Generating electricity is but one possible use for this gas. Microbial fuel cells have the advantage of generating electricity directly, without the need to extract or burn methane. In other words, it takes advantage of the natural chemical reactions that take place when microbes break down the sewage to make electricity.
How much electricity? In 2004, scientists estimated that worldwide, wastewater contains the potential to generate roughly as much energy annually as the output of 70 to 140 large nuclear plants! According to newer study, they seriously underestimated the amount of energy available from municipal wastewater. What’s more, the newer study also studied industrial wastewater and determined that it contains even more energy potential.
Every day, each one of us flushes energy down the toilet. The by-product of current treatment methods, sludge, presents an expensive disposal problem. Within a microbial fuel cell, all those germs would consume the sludge while generating plenty of electricity—which the wastewater treatment plant could sell. Potentially, what is now a waste stream could turn into an energy source. A microbial fuel cell could solve both the sludge problem and reduce our dependence on coal and petroleum products while generating plenty of electricity from an infinitely renewable resource.
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