Hydrogen Production Gets a Shock from Bacteria

Environmental engineers at Pennsylvania State University and a scientist from Ion Power have developed a process that enables bacteria to coax four-times as much hydrogen directly out of biomass than can be generated typically by fermentation alone. The researchers are using an electrically assisted microbial fuel cell (MFC) that does not require oxygen.

"This MFC process is not limited to using only carbohydrate-based biomass for hydrogen production like conventional fermentation processes. We can theoretically use our MFC to obtain high yields of hydrogen from any biodegradable, dissolved, organic matter -- human, agricultural or industrial wastewater, for example -- and simultaneously clean the wastewater," Dr. Bruce Logan, the Kappe professor of environmental engineering and an inventor of the MFC, said.
"While there is likely insufficient waste biomass to sustain a global hydrogen economy, this form of renewable energy production may help offset the substantial costs of wastewater treatment as well as provide a contribution to nations able to harness hydrogen as an energy source."

The new approach is described in a paper, "Electrochemically Assisted Microbial Production of Hydrogen from Acetate," which was released online and is scheduled for a future issue of Environmental Science and Technology. The authors are Dr. Hong Liu, postdoctoral researcher in environmental engineering; Dr. Stephen Grot, president and founder of Ion Power; and Logan.

Grot, a former Penn State student, suggested the idea of modifying an MFC to generate hydrogen.

In their paper, the researchers explain that hydrogen production by bacterial fermentation is currently limited by the "fermentation barrier" -- the fact that bacteria, without a power boost, can only convert carbohydrates to a limited amount of hydrogen and a mixture of "dead end" fermentation end products such as acetic and butyric acids.

However, giving the bacteria a small assist with a tiny amount of electricity -- about 0.25 volts or a small fraction of the voltage needed to run a typical 6 volt cell phone -- they can leap over the fermentation barrier and convert a "dead end" fermentation product, acetic acid, into carbon dioxide and hydrogen.

"Basically, we use the same microbial fuel cell we developed to clean wastewater and produce electricity. However, to produce hydrogen, we keep oxygen out of the MFC and add a small amount of power into the system," Logan said.

The researchers call their hydrogen-producing MFC a BioElectrochemically-Assisted Microbial Reactor or BEAMR. The BEAMR not only produces hydrogen, it simultaneously cleans the wastewater used as its feedstock. It uses about one-tenth of the voltage needed for electrolysis, the process that uses electricity to break water down into hydrogen and oxygen.

The Penn State researchers were supported by grants from the National Science Foundation, the U.S. Department of Agriculture, the Penn State Huck Life Sciences Institute and the Stan and Flora Kappe Endowment.

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