Could Hydrogen Breakthrough Revive The Fuel-Cell Car?

Researchers at Virginia Tech have found a way to efficiently extract hydrogen from plant materials, overcoming one of the obstacles that led the Obama Administration to put hydrogen fuel-cell technology on the back burner.
"We think this discovery is a game-changer in the world of alternative energy,” said Y.H. Percival Zhang, an associate professor of biological systems engineering. Zhang lead a Virginia Tech team that developed a way to produce large quantities of hydrogen from xylose, an abundant simple sugar that makes up 30 percent of the cell walls of plants.
Hydrogen is conventionally produced by steam reforming natural gas, a process that wastes some of the energy stored in the gas while releasing large amounts of CO2. In a 2009 interview with the MIT Technological Review, Energy Secretary Steven Chu identified the conventional source of hydrogen as the first of four obstacles to hydrogen fuel-cell technology for automobiles:
"I always was somewhat skeptical of it because, right now, the way we get hydrogen primarily is from reforming gas. That’s not an ideal source of hydrogen. You’re giving away some of the energy content of natural gas, which is a very valuable fuel."
Chu had just reduced the budget for fuel-cell vehicle development from $250 million to $70 million, betting that battery-powered electric vehicles could sooner reach the Obama Administration's goal of "a $20,000 personal vehicle that can compete with a 45- or even 50-mile-per-gallon internal combustion car."
Less is known about Obama's candidate to succeed Chu, Ernest Moniz, when it comes to hydrogen fuel-cell technology. But in a 2004 appearance at MIT, Moniz expressed a similar attitude: We "can't afford to have a focus on this direction impede serious approaches regarding security and the environment," he said of hydrogen fuel-cell technology.
At Virginia Tech, Zhang has been researching ways to use enzymes to extract hydrogen from plant biomass. Reported in a recent issue of Angewandte Chemie (subscription), the breakthrough came when the team submitted xylose to a cocktail of 13 enzymes, producing hydrogen at low temperatures:
To liberate the hydrogen, Virginia Tech scientists separated a number of enzymes from their native microorganisms to create a customized enzyme cocktail that does not occur in nature. The enzymes, when combined with xylose and a polyphosphate, liberate the unprecedentedly high volume of hydrogen from xylose…. 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. 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.
According to Virginia Tech, Zhang's discovery is endorsed by Jonathan R. Mielenz, the group leader of the bioscience division at the Oak Ridge National Laboratory:
“The key to this exciting development is that Zhang is using the second most prevalent sugar in plants to produce this hydrogen,” Mielenz told VT. “This amounts to a significant additional benefit to hydrogen production and it reduces the overall cost of producing hydrogen from biomass.”
Mielenz predicts Zhang's process could reach the $100 billion hydrogen marketplace in three years. Even if it does, Steven Chu named three more obstacles to hydrogen fuel-cell technology:
"The other problem is, if it’s for transportation, we don’t have a good storage mechanism yet. Compressed hydrogen is the best mechanism [but it requires] a large volume. We haven’t figured out how to store it with high density. What else? The fuel cells aren’t there yet, and the distribution infrastructure isn’t there yet. So you have four things that have to happen all at once. And so it always looked like it was going to be the distant future. In order to get significant deployment, you need four significant technological breakthroughs. That makes it unlikely."
Despite the cuts to its hydrogen program, DOE has been making progress on those obstacles as well. For example, it recently released a report on the viability of transporting hydrogen by blending it into the existing natural gas pipeline infrastructure.
"In the longer term, blending may provide an economic means of hydrogen delivery when the hydrogen is injected upstream and then extracted downstream for use in fuel cell electric vehicles or stationary fuel cells," the report concludes.

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