Coming Soon: Batteries that Run On (and Clean) Used Toilet Water
Tuesday, August 23, 2011
Humans should have a little more respect for dirty toilet water. In recent years, wastewater has become something of a commodity, with nuclear plants paying for treated wastewater to run their facilities, cities relying on so-called “toilet to tap” technology, and breweries turning wastewater into biogas that can be used to power their facilities. Soon enough, wastewater-powered batteries may even keep the lights on in your house or, at the very least, in the industrial plants that clean the wastewater.
Environmental engineer Bruce Logan is developing microbial fuel cells that rely on wastewater bacteria’s desire to munch on organic waste. When these bacteria eat the waste, electrons are released as a byproduct–and Logan’s fuel cell collects those electrons on carbon bristles, where they can move through a circuit and power everything from light bulbs to ceiling fans. Logan’s microbial fuel cells can produce both electrical power and hydrogen, meaning the cells could one day be used to juice up hydrogen-powered vehicles.
Logan’s fuel cells aren’t overly expensive. “In the early reactors, we used very expensive graphite rods and expensive polymers and precious metals like platinum. And we’ve now reached the point where we don’t have to use any precious metals,” he explained to the National Science Foundation.
Microbial fuel cells still don’t produce enough power to be useful in our daily lives, but that may change soon–Logan estimates that the fuel cells will be ready to go in the next five to 10 years, at which point they could power entire wastewater treatment plants and still generate enough electricity to power neighboring towns. There may also be ones that use–and in the process-desalinate–salt water, using just the energy from the bacteria.
And if the microbial fuel cells don’t work out, there’s another option: Chinese researchers have developed a photocatalytic fuel cell that uses light (as opposed to microbial cells) to clean wastewater and generate power. That technology is also far from commercialization, but in a few years, filthy water will power its own cleaning facilities one way or another.