Sustainable Energy

A New Source of Hydrogen for Fuel-Cell Vehicles

The prospects for carbon-neutral vehicles could get a boost from a new way to make hydrogen from biomass.

Transportation accounts for roughly a quarter of the world’s carbon dioxide emissions.

A new method for making hydrogen directly from plants could be an inexpensive way to generate fuel for alternative vehicles, perhaps paving the way for hydrogen refueling stations that rely on agricultural waste.

For several years, Percival Zhang, a professor of biological systems engineering at Virginia Tech, has been developing an enzymatic method to break complex sugars—like those found in plant material—into their component parts. Zhang’s process is “cell-free,” meaning it does not require microörganisms like those used in fermentation. Now he’s shown that it can be used to efficiently turn corn stover, the most abundant agricultural waste product in the United States, into hydrogen fuel.

Zhang and his colleagues have demonstrated that the process produces three times more hydrogen per unit of sugar than conventional fermentation methods.

The technology is still at an early stage and has been proved only at a small scale, using a two-milliliter reactor. But Zhang says the method is nearly as fast and energy-efficient as existing processes that use microörganisms to produce fuel, including cellulosic ethanol, from organic material.

His next goal is to increase the production scale from just a few milliliters to a full liter, and he hopes to have a process that could be implemented in fueling stations within three years. Even further in the future, he imagines, cars could have an onboard reactor that converts sugars into fuel. Zhang will pursue commercialization through a spinoff company he cofounded.

The potential costs of the technology remain uncertain, however. Though the recent work is “very elegant from the biochemical and engineering standpoint” and represents a much more efficient way to use biomass than microörganism-based fermentation, there’s a long way to go before a commercially viable process can be implemented at scale, says Jamie Williamson, a professor of molecular biology and chemistry at the Scripps Research Institute. The process depends on enzymes, which are expensive, and the cost of making the entire set of those required for Zhang’s technology could be quite high, he says. It’s also not clear yet that the enzymes will be stable enough on a large scale.

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