Scientists have found a way to turn human urine into electricity by mixing it with wastewater and feeding it to bacteria in specialized fuel cells, according to a study published in Results in Chemistry.
Treating wastewater takes a lot of energy and money, and the nutrients in what gets flushed typically go unused. Microbial fuel cells tackle both problems at once: Bacteria inside the cells break down organic material in the waste, producing electricity as they clean the water.
The big question has been how much urine to add for the best results.
To find out, a McGill University team set up four fuel cells, each split into two chambers. Over 14 days, they filled the cells with lab-made wastewater spiked with real human urine at 20%, 50%, and 75% strength. The researchers measured electricity production and pollutant removal at each level and identified which bacteria flourished in the mix.
Urine mixes in the 50% to 75% range produced more electricity and encouraged stronger bacterial growth on the cell's electrodes. Pollutant levels dropped by as much as 50% during testing.
"Urine contains essential ions and organic compounds that support rapid microbial activity, which improves power generation and pollutant breakdown," said Vijaya Raghavan, a McGill University bioresource engineering professor who co-authored the study, in a Tech Xplore article.
Two bacterial groups stood out as the main drivers of the process. Sediminibacterium appeared most frequently at the 50% urine mix, and Comamonas became the leading species at 75%. Both species digest organic matter in the waste and shuttle electrons to the electrode, which is how the cell generates its electrical current.
This kind of technology could mean cheaper, greener wastewater treatment in your community. The fuel cells could one day serve remote locations, emergency shelters, and communities not connected to a traditional sewage system, where building full-scale infrastructure is too expensive. The cells' electrical signals respond to the level of organic pollution in the water, meaning they could work as inexpensive sensors for checking water quality on the spot.
"Using urine as a resource supports sustainable sanitation and nutrient recovery, reducing pressure on freshwater systems," Raghavan said.
The technology is still in the lab stage, but continued work on fine-tuning urine-to-wastewater ratios and pinpointing the most effective bacterial species could bring it closer to everyday use.
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