News and analysis about energy in California with an eye toward renewables.

Breakthrough Claimed in Hydrogen Biofuel

Percival Zhang in his lab | Photo: Virginia Tech

Researchers at Virginia Tech are claiming a breakthrough in producing hydrogen fuel from a common plant sugar in a method that they say reaches efficiencies higher than 100 percent, offering the possibility of cheap, ecologically benign gas fuel for engines and fuel cells.

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The research team, which just published a study in the chemistry journal Angewandte Chemie, has apparently found a way to use enzymes extracted from so-called extremophile microorganisms' to break down xylose, the second most-common sugar found in plant tissues.

"Our new process could help end our dependence on fossil fuels," said Y.H. Percival Zhang, associate professor of biological systems engineering at Virginia Tech, in a press release. "Hydrogen is one of the most important biofuels of the future."

According to that press release, Zhang's team found a way to use microbial enzymes at relatively low temperatures -- around 120°F -- in combination with xylose and another enzyme called xylulokinase to create three times as much hydrogen from the chemical energy in the xylose as had been possible with earlier methods of hydrogen biofuel production.

According to that release:

The energy stored in xylose splits water molecules, yielding high-purity hydrogen that can be directly utilized by proton-exchange membrane fuel cells. Even more appealing, this reaction occurs at low temperatures, generating hydrogen energy that is greater than the chemical energy stored in xylose and the polyphosphate [xylulokinase]. This results in an energy efficiency of more than 100 percent -- a net energy gain. That means that low-temperature waste heat can be used to produce high-quality chemical energy hydrogen for the first time. Other processes that convert sugar into biofuels such as ethanol and butanol always have energy efficiencies of less than 100 percent, resulting in an energy penalty.

There are still major obstacles to use of hydrogen as a fuel, especially in the infrastructure arena. Hydrogen is notoriously hard to contain, leaking readily from pipes and storage tanks. Storage itself is an issue as well: hydrogen isn't particularly energy-dense, and to hold as much power as an equivalent volume of other fuels hydrogen must either be kept under pressure or captured chemically in a hydride or other compound.

Still, that's some exciting news from Zhang's team, with possible useful applications down the road a few years.


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About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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