Starch diet could power car of the future

Green cars of the future could run on a syrupy mixture of starch and water, according to new research.
Researchers have found a cocktail of enzymes that converts starchy syrups to hydrogen and carbon dioxide. The hydrogen can then be fed into a fuel cell to run an electric car, or even used in an ordinary combustion engine.
The team says its technology is the solution to three major hurdles that stand between us and a hydrogen economy: safe and cheap production, storage and transportation of hydrogen.
The method hinges on a mixture of 13 enzymes, normally found separately in plants, rabbits, bacteria and yeast, but never together in nature. When the enzymes are added to starch and water, "the enzymes use the energy in the starch to break up water into CO2 and hydrogen," says Y-H Percival Zhang of Virginia Tech in the US.
The CO2 is separated from the hydrogen by a membrane and returned to the atmosphere. Because the starch is from biomass - wood and plants - the same amount of CO2 is released by the conversion as was taken out of the atmosphere by plants to produce the starch in the first place. So the process is carbon neutral.
Temperature limit
The hydrogen can then be used to run a fuel cell, and power an electric car. It could also be used to run an ordinary combustion engine, though Zhang does not favour this option as it is less energy efficient.
"Most car companies are putting some money into developing hydrogen cars," says Kylie Vincent of Oxford University in the UK. "A straightforward, cheap strategy like this will be important in allowing hydrogen energy technologies to come into common use."
Zhang, who plans to make a prototype toy car within three years, says his technique could produce hydrogen for as little as $8 for 4 kilograms of hydrogen. This could fuel a car for more than 300 miles.
He acknowledges that the enzymes used - sourced from a chemical supplier - are expensive. But he believes he can produce cheaper ones that would also work at higher temperatures.
For now, the researchers have shown that the conversion can happen at 30°C. Zhang believes he can produce enzymes that would convert starch to hydrogen equally well at temperatures up to 100°C – an important improvement if the cocktail is to be used in working cars.
Off-the-shelf fuel
The team's vision is that one day, you could buy starch in a supermarket, pour it into your engine and go. "We plan to use cellulose from plants, such as wood chip and agricultural waste," says Zhang. The enzymes would produce hydrogen in real-time, as your engine needs it.
"One challenge for getting hydrogen into use is finding a way of storing it," says Vincent. "That, and the public perception of hydrogen as dangerous and flammable. This way of storing hydrogen is lightweight, safe and easily distributed. It is no more dangerous than the petrol we use at the moment, and it is totally safe in the form it is poured into the engine."
"Other storage materials that will take up hydrogen tend to be heavy metals," she explains. "But this is a lighter way of carrying hydrogen around."
All in all, Vincent is impressed. She says Zhang's technique may not be an ideal end-solution for the hydrogen economy: like all biofuels, it relies on biomass, and therefore land, to produce the starch. But she thinks it could, in the short term, be a good stepping stone to introduce a hydrogen economy.
"If the financial support is sufficient, within three to five years, this technology will be applied to high-end markets such as cellular phone and laptop batteries," says Zhang. "After another three to five years it will be integrated with hydrogen-fuel-cell vehicles. If everything goes well, we will see the first real-size sugar car on the way after eight to ten years."
Journal reference: PLoS One (DOI: 10.1371/journal.pone.0000456)
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