Everybody poops, and all of that poop adds up: Cities in the U.S. have to deal with around 12 trillion gallons of wastewater every year. It’s a messy process that also has a massive carbon footprint. Industrial wastewater treatment–cleaning all of the filth from factories and power plants–takes even more energy. Overall, treating American wastewater uses about as much energy as it takes to power 10 million homes.
A new kind of wastewater plant can run itself on its own waste instead–while taking carbon dioxide out of the air at the same time. As a bonus, it also produces renewable fuel for hydrogen fuel cell cars.
“It’s three benefits in one system,” says Z. Jason Ren, an associate professor of engineering at the University of Colorado-Boulder who helped design the new treatment.
The system is powered by bacteria that can split hydrogen out of water. “They basically convert the chemical energy from the wastewater into electrical energy to split the water,” he says.
The process creates hydrogen gas that can be used as fuel or as a clean source of electricity. When the water splits, it also combines with calcium to create calcium hydroxide–something that can capture CO2 from the air and turn it into limestone that can be used for manufacturing.
It’s a system that would work well at coal power plants, which have to deal with huge amounts of both wastewater and carbon emissions. “Power plants have the new regulation coming up from Obama saying they have to reduce CO2, and that’s something we can help with,” says Ren.
“It’s actually an ideal location,” he says. “They already need to spend a lot of money to clean their wastewater, they already need a lot of money to clean up their solid waste.” He points to the example of Duke Energy, which was fined over a hundred million of dollars when it spilled coal ash in a local river. “They also have to spend a lot of money to capture their CO2 emissions. So this helps them to deal with all these things together.”
At the moment, the system is still a proof of concept, but the researchers have already been approached by large utility companies who are interested in using the technology. “There are definitely some technological challenges we have to overcome,” Ren says. “How cheap we can get, how efficient–those are the types of questions we have to answer.”