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Researchers study organic enzymes as future car fuel

Posted: 29 May 2007 ?? ?Print Version ?Bookmark and Share

Keywords:organic enzymes? future car? fuel cell?

University and government researchers are investigating whether a blend of starch, enzymes and water could produce hydrogen fuel for future cars.

"Our energy conversion efficiency is so high that we believe we can provide the fuel for all future vehicle transportation," claimed Percival Zhang, an engineering professor at Virginia Tech.

The Energy Department has mandated that ethanol from plant sources should power 30 percent of vehicles by 2012, and that a "hydrogen economy" based on fuel-cells should power vehicles by 2020. Teams from Virginia Tech, University of Georgia and Oak Ridge National Laboratory claim their technology exceeds the energy department's goals with a biomass/fuel cell conversion process they claim is cheaper, more compact and organic.

'Organic' answer
While hydrogen can be converted into electricity by a fuel cell to drive a car engine, the search continues for a way to release hydrogen on-demand and at a rate sufficient to power a vehicle fuel cell. The research team claims to have found an "organic" answer that mixes starch (derived from biomass) with water. A blend of organic enzymes was added to release hydrogen from water when a driver of a future hydrogen-powered car steps on the accelerator.

"We envision that future vehicles will store solid starch, then mix it with water from which our enzymes release the water's hydrogen to fuel cells which produce the electricity to drive a vehicle's motor," said Zhang.

Using their technology, the researchers claim the requisite 300-mile range consumers expect from gasoline-powered vehicles would require just a 12-gallon tank. A full tank would hold about 27.22kg of starchthe equivalent of about 4.08kg of hydrogen. About 2.72kg of starch produces roughly the same energy as about one gallon of gasoline.

The key enabler, Zhang said, is a proprietary blend of 13 organic enzymes not found combined in nature, but which were discovered by Zhang and his colleagues. The team has applied for a provisional patent covering the process.

CO2 check
The only drawback reported so far by the researchers is that the process releases carbon dioxide. That's because they used C6H10O5a polysaccharide. Plants store energy in polysaccharides and release their stored energy using naturally-occurring enzymes. The researchers main task was to design an enzyme blend that could break up sugar-water into CO2 and hydrogen at a fast enough rate to power a car-sized fuel cell.

A membrane was used in the laboratory to bleed off CO2 while hydrogen was used to feed a fuel cell, which coverted it into electricity to drive motors. The starch-water conversion reaction takes place at normal atmospheric pressure at 30C.

The researchers next plan to try out their technique on small fuel cells for cellphones before integrating it with polymer electrolyte membrane cells for testing in vehicles. They hope to increase the efficiency of their process while lowering the enzyme blend cost.

- R. Colin Johnson
EE Times




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