Petroleum is a finite resource, and extracting energy directly from it is causing severe environmental damage. Alternative sources of energy are sorely needed.
There are at least two complications to this issue. One is that carbon-based combustion for energy will not go away soon. A more environmentally friendly source of carbon for combustion than fossil fuels is still needed in the short term.
A second complication is that no matter what clean energy sources are applied in the future -- wind, solar, etc. -- carbon-based molecules will still be needed. For example, chemists will still need to synthesize pharmeceuticals.
Mark Mascal and Edward Nikitin at the University of California (Davis) have shown that these complications can be addressed with biofuels. They have easily, and efficiently, converted cellulose into solvents of high energy content.
Chewing up cellulose into a useful fuel.
Historically, scientists have used microorganisms to convert cellulose into ethanol by fermentation. This wastes 33% of the carbon in cellulose, and is not energy-efficient. Mascal and Nikitin instead directly converted cellulose into 5-(chloromethyl)furfural, which is easily converted into useful biofuels.
Finely divided cellulose was added to a salty acid solution, which was all added to an incompatible oily solvent. This mixture was continuously stirred to keep everything mixed together, and heated for a little less than one day. More salty acid solution was subsequently added, with a further half day of heating.
Afterwards, the mixture was cooled, and the oil spontaneously separated from the salty acid. The oil layer contained the solvent as well as the biofuel precursor. The solvent and biofuel precursor were easily separated from one another by chromatography.
Isolating biofuels.
The biofuel precursor was a mixture of four oils, in 85% total yield. Of the four, the oil recovered in the highest yield (71%) was 5-(chloromethyl)furfural (CMF). This 85% yield is far greater than that obtained from fermentation (67% at best, under the most ideal conditions imaginable).
CMF is not a biofuel. However, it can be easily converted into ethoxymethylfurfural (EMF), in nearly 100% yield, by simply stirring it in ethanol. EMF is a potential biofuel, of virtually identical energy content as gasoline, and has been investigated for possible commercial use.
Furthermore, the use of ethanol can be avoided entirely. Under gentle conditions, CMF can instead be converted into 5-methylfurfural (MF), 2-5-dimethylfuran, or 2,5-dimethyltetrahydrofuran. Similarly to EMF, these are also potential biofuels.
Safety of the biofuels.
An important question is whether the potential biofuels produced by these scientists are toxic. EMF and MF are both considered to be, at worst, mild irritants. Additionally, they do not give off much vapor at room temperature, further reducing risk of exposure.
The future.
Further work on this system needs to apply Mascal and Nikitin's process to "raw" cellulose instead of finely divided cellulose. In the meantime, they have made a giant step forward for environmentally responsible use of the planet's limited resources. Cellulose can now be efficiently and easily converted into useful biofuels and carbon sources needed by scientists and the general population.
for more information:
Mascal, M.; Nikitin, E. B.
Direct, high-yield conversion of cellulose into biofuel.
Angew. Chem. Int. Ed. 2008, 47, 7924-7926.