Monday, November 26, 2007

Making Fuel from Leftovers

Continued from page 1

By Jennifer Chu

The entire process generated 288 percent more energy than the electricity required to produce the reaction. Logan and his colleagues estimate that, compared with conventional electrolysis, which has a 60 percent efficiency rate, BEAMR achieved an 82 percent efficiency rate.

Logan says that his recent experiment shows that acetic acid could be a rich source of hydrogen-generating material under specific conditions. This suggests that researchers may be able to get more hydrogen out of biomass than was previously thought. Another implication from the study: cellulose may turn out to be better suited for hydrogen production than ethanol fuel is because using cellulose for ethanol involves a more complicated process.

"If you think of cellulose as a starting material to make ethanol, people have to add enzymes to break it down to sugars, and then those can be fermented into ethanol," says Logan. "But we can use cellulose directly to make hydrogen."

He says that a potential first application for the technology may be in powering farms, wastewater treatment plants, and other facilities with large amounts of unused biomass. However, scaling BEAMR up to commercial applications may take some rejiggering. The materials used in the system, particularly the platinum cathode in the reactor, would be very expensive if manufactured at a large scale. In the future, Logan's lab plans to reduce the cost of the reactor's components, and it has already started looking for alternatives to platinum.

Lars Angenent, assistant professor in the Department of Energy, Environmental, and Chemical Engineering at Washington University, works to optimize fermentation processes to produce bioenergy. He says that while Logan's technology successfully "circumvents biological limitations of hydrogen production," bringing it to a commercial level may pose challenges.

"Scale-up will be the problem," says Angenent. "This must be commercially viable while sustaining high efficiencies."