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Enzyme Cocktail Generates High Volume Hydrogen from Biomass

H2 hydrogen icon


Bioengineers at Virginia Tech in Blacksburg, with colleagues from elsewhere in the U.S. and Mexico, developed a process to inexpensively extract large volumes of hydrogen fuel from any type of plant matter. The team led by biological systems engineering professor Y.H. Percival Zhang, published its findings online in a recent issue of the journal Angewandte Chemie International Edition (paid subscription required).

Zhang, with associates from Virginia Tech, University of Georgia, Oak Ridge National Lab, and Centro de Investigación y de Estudios Avanzados-Merida in Mexico, generated hydrogen from xylose, a common and abundant sugar found in the cell walls of a wide variety of plants. Among the sources of xylose for biofuels are agricultural refuse, such as straw, pecan shells, cottonseed hulls, and corncobs, which makes Zhang’s process feasible with biomass made from non-food plant materials, and thus not likely to affect food prices.

Xylose has been considered a potential source for hydrogen, but the amounts of hydrogen have been limited by the activity of microorganisms that produce the catalytic enzymes used to react with xylose. The microorganisms, both natural and engineered, tend to use their energy to grow and reproduce rather than split hydrogen from water (H20) molecules. Zhang’s team worked around this obstacle by producing a synthetic enzyme cocktail, derived from microorganisms, but that also thrives at higher temperatures.

The researchers combine the enzyme mix with xylose and polyphosphates — inorganic salts from phosphoric acid — at temperatures of 122 degrees F and normal atmospheric pressure. The chemical reactions that result produce three times as much hydrogen as other hydrogen-producing microorganisms. The waste heat generated by the process is sufficient to heat the reactor and thus produce more energy than is stored in the xylose, returning an energy efficiency greater than 100 percent.

The hydrogen is produced by splitting hydrogen from the water atoms that can be used directly in proton-exchange membrane, sometimes called polymer electrolyte membrane, fuel cells. In these fuel cells, a catalyst, usually platinum, splits the hydrogen into positive ions and negatively charged electrons. The membrane then allows the positive ions to pass through to a cathode, while the negatively charged electrons travel through an external circuit creating an electric current. The only byproduct of hydrogen fuel cells is water.

Zhang founded a company in Blacksburg, Cell-Free Bioinnovations Inc., which says on its Web site is “developing cell-free platform technologies that enable low-cost production of biochemicals and biofuels and increase the power density generated by enzymatic biofuel cells.” An online directory of corporations lists Zhang as the company’s president.

Virginia Tech says the commercial market for hydrogen derived from natural gas is valued at about $100 million, which requires the use of a non-renewable fossil fuel, and contributes to the accumulation of greenhouse gases. “It really doesn’t make sense to use non-renewable natural resources to produce hydrogen,” says Zhang. “We think this discovery is a game-changer in the world of alternative energy.”

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2 comments to Enzyme Cocktail Generates High Volume Hydrogen from Biomass

  • Dennis Mingus

    Low cost hydrogen in large volume is great, but the problem is in how to use it. We should not be trying to place fuel cells in cars. We can use fuel cells in power plants and supply an electric grid. Building an electric grid over the roads that cars can hookup to, as is done in bumper cars in an amusement park, would allow all electric cars with vary inexpensive and small batteries. The batteries shouldn’t need to carry you more than 20 or 25 miles, making them smaller and cheaper. The cars would also be much cheaper. The government with the power companies could build the electric grid over the roadways.

  • Lots of good ideas there Dennis. Thanks for sharing them here. – AK