New Technology to Make High Power Biofuel

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Biofuel engineers at the University of Wisconsin at Madison have been able to convert fructose, the sugar found in fruits such as apples and oranges into a new type of liquid biofuel for cars which, it is claimed, packs 40% more energy than ethanol (ethyl alcohol).

Ethanol is currently the only car fuel made in large quantities from biomass sources such as corn, sugarcane and some other plants containing large chains of carbohydrates. In their plant form, these long carbohydrate molecules comprise six carbon atoms and six oxygen atoms. However, car engines like a leaner form of carbohydrate molecule, i.e. a molecule with carbon atoms ranging between 5 and 15 and with very little oxygen atoms.

Ethanol, the biofuel commonly in use has, however, relatively high levels of oxygen. This reduces its energy density which besides having the effect of making it evaporate readily leaves it liable to water contamination by absorbing atmospheric humidity. To separate the fuel from water, distillation in needed which indeed is an energy-intensive process.

According to James Dumesic, a professor of chemical and biological engineering and the leader of the research team at the University of Wisconsin, his team could discover a process that produces a liquid fuel having energy density comparable to petrol. The process involves use of enzymes to convert plant carbohydrates into fructose. The next step is to convert this fructose into hydroxymethylfurfural (HMF) by using an acid catalyst and a solvent with a low boiling point. The process leads to the expulsion of three oxygen atoms. By exposing HMF, which is in gaseous form, to a copper-ruthenium catalyst two more oxygen atoms are kicked off an HMF gets converted into the final product 2,5- dimethylfuran (DMF). This is the liquid biofuel, which can be used as a general fuel for transportation.

More research is, however, needed before the technology can be commercialised. Says Dumesic, "There are some challenges that we need to address, but this work shows that we can produce a liquid fuel from biomass that has energy density comparable to petrol."

It may be noted that both biofuel and fossil fuels emit carbon dioxide (Co2), the principal greenhouse gas blamed for climate change. However, biofuels are environmentally-friendlier than fossil fuels although not completely clean because energy has to be harvest and process the biomass. This makes biofuels carbon-positive and not carbon-neutral as is generally believed.

Actually, in biofuels plants suck carbon dioxide out of the atmosphere in order to grow and this carbon is returned back to the atmosphere when the fuel is burned. However, the burning of fossil fuels pumps out the carbon that got stored for millions of years in the deep interior of earth. The contribution of the fossil fuels to the atomospheric pollution is, therefore, for more as compared to the biofuels.


Invention Intelligence , July-August 2007