“Green” gasoline?

Cellulosic ethanol? How about cellulosic gasoline and diesel fuel instead?

A research team from the University of Wisconsin at Madison has come up with what may be an economic way to produce what a UW press release calls “green gasoline” from the sugars in corn stalks and stover and other plant residues that the Department and Energy and other are targeting for production of alcohol fuels. The paper, published last week in the online edition of Science magazine, explains how it is possible, using catalysts common to the oil refining industry, to turn the sugars in plant wastes directly into gasoline and diesel, not alcohol.

The research team led by James Dumesic of Wisconsin’s department of chemical and biological engineering identified a “catalytic approach for the conversion of carbohydrates to specific classes of hydrocarbons for use as liquid transportation fuels, based on the integration of several flow reactors operated in a cascade mode, where the effluent from the one reactor is simply fed to the next reactor. This approach can be tuned for production of branched hydrocarbons and aromatic compounds in gasoline, or longer chain, less highly-branched hydrocarbons in diesel and jet fuels.”

The university press release notes that the process begins by adding a solid catalyst (identified in the Science article as Pt-Re – or Platinum-Rhenium—a common catalyst in the petroleum refining industry) to a water solution containing the sugar-rich cellulosic bio-wastes. This, said the press release, leads to “the formation of an organic oil-like solution floating on top of the water. The oil layer, which is easily transportable, contains molecules of acids, alcohols, ketones and cyclics.” Dumesic calls these “functional intermediates” to conventional transportation fuels.

They can then be easily upgraded to different forms of fuels. “This is the same fuel we’re currently using, just from a different source,” says Dumesic. “It’s not something that burns like it – it is it.”

The Dumesic process appears to be simpler and less expensive than the approach that many researchers have taken toward converting plants wastes into ethanol, which can be blended into conventional fossil fuels for powering cars and trucks. It is fairly easy to convert high-sugar plant substances, such as corn kernels and sugar cane, into alcohol, but much more difficult and expensive to turn plant wastes into fuel. President Bush famously cited plans to turn switchgrass (Panicum virgatum) into alcohol in his 2006 State of the Union address, with few results to date.

The Science Express article concludes with the usual caveats. More research is needed to demonstrate just how this scales up to commercial production. The initial research had funds from the U.S. Department of Energy and the National Science Foundation.