New research shows that sewage contains a source of energy that can be harvested using hungry bacteria.

Domestic sewage incorporates various organic substances, mainly from toilets and kitchens, that are harmful to the environment but also hold the potential to generate energy. Researchers from Ghent University, in Belgium, have now discovered how to efficiently extract this energy from the wastewater to provide for energy-neutral sewage treatment.

Dr. Francis Meerburg, researcher at Ghent University's Center for Microbial Ecology and Technology. Image credit: University of Ghent. "The levels of organic matter in sewage are too low to be directly recovered," says Dr. Francis Meerburg, researcher at the university's Center for Microbial Ecology and Technology. "We investigated how we can use bacteria to capture this material. Our approach is unique because we have developed a high-rate variation of the so-called contact-stabilization process."

The process involves periodically starving bacteria in a kind of "fasting regimen." Afterwards, wastewater is briefly brought into contact with the starved bacteria, which gobble up the organic matter without ingesting all of it. This enables harvesting of the undigested materials for the production of energy.

According to the researchers, by using this contact-stabilization process, up to 55% of the organic matter can be recovered from sewage—as compared with existing processes that generally cannot recover more than 20%-30%. The researchers calculated that this amount can provide sufficient energy to completely treat sewage without the need for external electricity.

Industrial partners have already shown interest in the process, with DC Water—which serves the U.S. capital city—currently performing a contact-stabilization trial as part of its water