Dr. Bruce Logan, professor of environmental engineering, and his research group have shown they can boost hydrogen production 43 percent by using a continuous hydrogen release fermentation process. He explains that by using certain industrial wastewater as feedstock, the approach offers an abundant, "green," local source for hydrogen and potentially makes it a cheaper fuel than gasoline.
"Continuous fermentation is not hard to do and the high volumes of gas produced make it a potential source of supply for a wide variety of fuel cell applications besides cars and buses, including home power generation and the micro-fuel cells being developed for consumer products such as laptops, cell phones, smoke alarms, and calculators," Logan adds.
Logan and Dr. Sang-Eun Oh, postdoctoral fellow; Dr. In S. Kim, professor of environmental engineering, Kwang-Ju Institute of Science and Technology, and Steven Van Ginkel, doctoral candidate, are the authors of a paper, "Biological Hydrogen Production Measured in Batch Anaerobic Respirometers," published in the current (May) issue of the journal, Environmental Science and Technology. The paper details the group's experiments comparing the standard fermentation method, in which hydrogen is released from the processing vessels intermittently, with a method in which the gas is released continuously.
In the Penn State experiments, fermentation was conducted with bacteria from ordinary garden soil. The soil, collected from local farmland, was heat treated to kill hydrogen-consuming bacteria. While the heat treatment also kills non-hydrogen producing soil bacteria, it leaves hydrogen-producing bacteria in a dormant spore form that revives as soon as it is put in suitable conditions.
The researchers mixed the heat-treated soil with individual samples of glucose, sucrose, cellulose, lactate, potato starch and molasses. Fermentation of both glucose and sucrose with the heat-treated soil under slightly acidic conditions in the absence of oxygen produced high concentrations of hydrogen gas. Releasing the gas continuously during glucose processing resulted in 43 percent more hydrogen than when the gas was released intermittently.
Logan notes that wastewater from confectioners, canneries, sugar refineries, and other industries are rich in glucose and sucrose. "The conversion of the chemical energy in these sugars to electricity in fuel cells via hydrogen gas, provides a method for wastewater treatment and renewable energy production in one step. The greatest savings at treatment plants may result from reducing costs for aerators since aeration is the major operational expense at most wastewater treatment plants," says the Penn State researcher.
In addition, methane could also be generated via the same process and from the same materials to provide an additional source of clean energy for fuel cells.
Logan says, "Both hydrogen and methane production via fermentation could save money spent on aeration while at the same time making a wastewater treatment plant into a local power plant."
Van Ginkel notes that, "Generating hydrogen by fermentation is not new. Batch fermentation was used during World War II to produce industrial solvents for ammunition production. Small amounts of hydrogen produced early in the fermentation process were not recovered.
However, the industry later switched to steam reformation of petroleum to produce these industrial solvents when oil was cheap.
"Now, that oil has become more expensive, more efficient ways to generate hydrogen, for example the continuous fermentation processing method, may help us cross the barrier to realizing hydrogen's promise as the fuel of the future," he adds.
The research was supported by a grant from the National Science Foundation. Dr. Oh's participation was supported by Brain Korea 21 program funding which supports sending Korean graduate students abroad for study and research.
Journal
Environmental Science & Technology