Now this is interesting! The shift to biofuels, based not on diesel but hydrogen fuel cells just became a whole lot easier.
May 23, 2007
Researchers at Virginia Tech, Oak Ridge National Laboratory (ORNL), and the University of Georgia propose using polysaccharides, or sugary carbohydrates, from biomass to directly produce low-cost hydrogen for the new hydrogen economy.
According to the DOE, advances are needed in four areas to make hydrogen fuel an economical reality for transportation: production, storage, distribution, and fuel cells. Most industrial hydrogen currently comes from natural gas, which has become expensive. Storing and moving the gas, whatever its source, is costly and cumbersome, and even dangerous. And there is little infrastructure for refueling a vehicle.
Using synthetic biology approaches, Zhang and colleagues Barbara R. Evans and Jonathan R. Mielenz of ORNL, and Robert C. Hopkins and Michael W.W. Adams of the University of Georgia, are using a combination of 13 enzymes never found together in nature to completely convert polysaccharides (C6H10O5) and water into hydrogen when and where that form of energy is needed. This “synthetic enzymatic pathway” research appears in the May 23 issue of PLoS ONE, the online, open-access journal from the Public Library of Science.
The vision is for the ingredients to be mixed in the fuel tank of your car, for instance. A car with an approximately 12-gallon tank could hold 27 kilograms (kg) of starch, which is the equivalent of 4 kg of hydrogen. The range would be more than 300 miles, Zhang estimates. One kg of starch will produce the same energy output as 1.12 kg (0.38 gallons) of gasoline.
Since hydrogen is gaseous, hydrogen storage is the largest obstacle to large-scale use of hydrogen fuel. The Department of Energy’s long-term goal for hydrogen storage was 12 mass percent, or 0.12 kg of hydrogen per one kg of container or storage material, but such technology is not available, said Zhang. Using polysaccharides as the hydrogen storage carrier, the research team achieved hydrogen storage capacity as high as 14.8 mass percent, they report in the PLOS article.
The PLOS article gives all the details:
The stoichiometric reaction is C6H10O5 (l)+7 H2O (l)→12 H2 (g)+6 CO2 (g). The overall process is spontaneous and unidirectional because of a negative Gibbs free energy and separation of the gaseous products with the aqueous reactants.
Enzymatic hydrogen production from starch and water mediated by 13 enzymes occurred at 30°C as expected, and the hydrogen yields were much higher than the theoretical limit (4 H2/glucose) of anaerobic fermentations.
The unique features, such as mild reaction conditions (30°C and atmospheric pressure), high hydrogen yields, likely low production costs ($~2/kg H2), and a high energy-density carrier starch (14.8 H2-based mass%), provide great potential for mobile applications. With technology improvements and integration with fuel cells, this technology also solves the challenges associated with hydrogen storage, distribution, and infrastructure in the hydrogen economy.
BTW, the graphic is from an article about a similar technology developed at Oxford.
Dr Roger Welch from University of Oxford said: “We are delighted to see the invention powering a useful device, in this case a digital watch, and believe that this marks a milestone in the development process to improve the power density and lifetime of the enzymes. We are very excited about the commercial and environmental benefits of these latest developments since it has the potential to provide the world with a clean and cost effective way of locally generating electricity”.