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Bioengineer Hong Liu is turning waste into watts.
Hong Liu and her son; photo by Dennis Wolverton

One-year old Joshua Fan plays with the microbial fuel cell his mother, bioengineer Hong Liu, is developing to turn biological waste into clean energy. Photo: Dennis Wolverton

Changing a baby’s diaper is one of the least inspiring activities imaginable. However, when Hong Liu changes her 1-year-old son, Joshua, she finds herself imagining a cleaner, brighter future, in which biological waste becomes a source of electricity for houses and hydrogen for cars.

Rinsing out a diaper (and flushing gallons of water to a distant treatment plant) or tossing out a disposable (and shipping it to a landfill), Liu thinks about a different kind of waste, about the inefficient use of resources.

“I think about all this wastefulness,” she says. “It is my hope that we can make use of biological waste, collect energy from it, and not send it to some central place for disposal.”

For Liu, extracting energy from wastewater is no pipe dream. She is developing a microbial fuel cell as a way of harnessing electricity from wastewater. On her lab bench in the Department of Biological and Ecological Engineering, she demonstrates a prototype. A few ounces of murky water sandwiched between glass plates generate a steady trickle of electrons, thanks to thriving colonies of bacteria.

“It turns out that some bacteria can transfer electrons from organic matter,” says Liu, who arrived at OSU in August after completing post-doctoral research at Penn State University. “Nobody ever tried sticking electrodes into wastewater; we were the first to do it for purifying domestic wastewater.”

As the microbes feed on organic waste, they kick out electrons that can be picked up by a carbon electrode. The current is just a trickle —about a half watt per square meter—but Liu has been able to increase electricity production by 3,700 percent in two years.

Working with Bruce Logan at Penn State and Stephen Grot of Ion Power, Liu induced microbial fuel cells to produce hydrogen gas—potentially the wonder fuel of the future since burning it produces only water.

Their discovery, which bears the illuminating name of BEAMR (“bio-electrochemically assisted microbial reactor”) won a Breakthrough Award from Popular Mechanics magazine in 2005. Liu envisions BEAMR fuel cells that will make wastewater treatment economically feasible.

“In developing nations where waste treatment may be too expensive, making a waste treatment plant almost energy self-sufficient might mean the difference between affordable treatment of wastes and no treatment at all,” she says. “The main challenge is the cost of electrode material, so we hope to find a more affordable option.”

Liu doesn’t foresee her microbial fuel cell replacing existing sewage treatment systems. Instead, she foresees portable BEAMR units providing water purification and electricity where they don’t already exist. She envisions a unit small enough to be loaded into a truck and hauled to a rural village where it would sit outside, purifying toilet and sink water for irrigating outdoor plants. The produced electricity would power a small water pump and a few lights. The portable units also might be useful in disaster zones, where power and water treatment have been disrupted.

Liu got her first exposure to the usefulness of organic waste shoveling “fertilizer” on her grandparent’s farm in the small town of Kazuo in northern China. Leaving the farm, she attended college in Harbin, a frosty industrial city famous for its ice sculptures. She earned degrees in civil and environmental engineering before leaving China in 2003 to take a post-doctoral position at Penn State. She joined the OSU faculty in 2005 to continue her research developing microbial fuel cells.

“Most impressive is that people here really care about people,” Liu said. “There is so much work to be done that you cannot do everything yourself. You have to work with others, and people here really want to collaborate.”

Liu thinks she will return to China with her son one day. She hopes that by then she will be able to show Joshua microbial fuel cells that she developed at OSU, bringing clean water and light to her homeland.