Enzymes convert biomass starches for fuel cells

By Susanne Retka Schill
Researchers at Virginia Tech, Oak Ridge National Laboratory (ORNL) and the University of Georgia have proposed using polysaccharides from biomass to directly produce hydrogen in a low-temperature, low-atmospheric-pressure process.

Using synthetic biology approaches, the process adds a combination of 13 enzymes never found together in nature to a mixture of starch and water. The enzymes use the energy in the starch to break up the water into carbon dioxide and hydrogen, said lead researcher Y.H. Percival Zhang, assistant professor of biological systems engineering at Virginia Tech in Blacksburg, Va. A membrane bleeds off the carbon dioxide, and the hydrogen is used by the fuel cell to create electricity. Water, a product of the fuel cell process, is recycled for the starch-water reactor. Laboratory tests confirm that it all takes place at a low temperature of about 86 degrees Fahrenheit and under low atmospheric pressure.

The research was based on Zhang's work with cellulosic ethanol production, and ORNL and University of Georgia researchers' work with enzymatic hydrogen production. According to Virginia Tech, the researchers were certain they could put the processes together. Zhang's colleagues in the project include Barbara Evans and Jonathan Mielenz of ORNL, and Robert Hopkins and Michael Adams of the University of Georgia.

The next step will be to increase reaction rates and reduce enzyme costs, Zhang said. He described the energy conversion efficiency from the sugar-to-hydrogen fuel cell system as extremely high-more than three times higher than a sugar-to-ethanol internal-combustion-engine system. "It means that if about 30 percent of transportation fuel can be replaced by ethanol from biomass as the DOE proposed, the same amount of biomass will be sufficient to provide 100 percent of vehicle transportation fuel through this technology," Zhang said.