Hydrogen has potential as a clean-burning fuel. It leaves behind only water as it burns. But as a scalable alternative to fossil fuels, it's yet to make good: most methods of making large amounts of hyrdrogen require energy (often from fossil fuels) to power its production, which sort of defeats the purpose. But a new energy-efficient way to make hydrogen using wastewater and sea water could turn a energy-intensive water treatment plant into a source of hydrogen.
Bruce Logan, professor of environmental engineering at Penn State University, has been working on bacteria that can serve as a cog in a fuel cell. In the right combination, they chew through the organic materials in wastewater and release electrons that can be harvested as electricity—or turned into hydrogen.
This early technology has been bubbling slowly in Logan's lab for a while now, as his team has determined just the right combination of bacteria that create the desired effect. Back in 2009, Logan and and his team figured out that running a measured jolt of electricity through a battery containing these bacteria enervated the bugs, causing them to get going on breaking down the organics to release hydrogen.
Now his team has found a way to make hydrogen without consuming that electric energy. In a new study published on September 19 in the Proceedings of the National Academies of Science, Logan and lab member Younggy Kim showed how the hydrogen production could be powered by salt water.
Desalination—extracting salt from water—soaks up energy. So, it makes sense that the reverse process would release it, Logan explains. Reverse desalination releases the energy necessary to get the bacteria going. With the right amount of salt water nearby, "You can hitch a wastewater treatment to a hydrogen production plant without any external energy," Logan told Fast Company.
While the concept works in the laboratory, it's too soon to say if this technology can perform as needed on a large scale. "Right now the main barriers are, can we do this on a large scale, and can we do this economically," Logan said.
For the time being, Logan sees value in being part of a larger movement to chip away at the renewable energy issue. "People are investing large amounts of money into technologies that have large scale impacts on energy production," Logan said, "But there are ways to make the same kind of change from the summation of smaller advances."
Turning the energy story on its head, Logan says an energy efficient way to treat wastewater could be used in poor countries like China and India, which don't have and won't afford the energy cost of sanitation for the entire country, as it is designed in countries like the U.S. Logan's energy-efficient wastewater cleaner may one day change that.