One of the critical problems identified with ‘peak oil’ – that point where stocks of petroleum begin to inexorably decline – is the resultant shortage and expense of aviation jet fuel. As traditional jet fuel sources decline, it’s bad enough for a world that’s knit together by (relatively) inexpensive air travel, but there’s another problem – the lack of an alternative source. Bio-fuels made from agricultural products simply do not have enough energy density to function as jet fuel. To address this problem – and find one of those inimitable ‘technological fixes’ – a team from the University of Wisconsin (Madison, USA) actually started with a problem of their own.

The team had done considerable work with conversion of plant sugars into transportation fuel. The problem was that these sugars degraded (broke down) rather quickly into two not very useful substances – levulinic acid and formic acid. So the team decided not to fight the problem of degrading sugars and instead find a way to use the two acids.

The discovery, then, was to use metal catalysts to react with the acids to form gamma-valerolactone (GVL). Currently GVL is made in small quantities for herbal foods and perfumes, but using only basic lab equipment and inexpensive catalysts, the research group converted a water solution of GVL into jet fuel. (Technically, they produce a pure stream of alkenes with a fairly pure stream of carbon dioxide.)

“The hydrocarbons produced from GVL in this new process are chemically equivalent to those used in the present infrastructure,” says Alonso [post doctoral student, UW-Madison]. “The product we make is ready for the jet fuel application and can be added to existing hydrocarbon blends, as needed, to meet specs.”

The biggest barrier to implementing the renewable fuel is the cost of GVL. Until now, says Dumesic [Steenbock Professor of Chemical and Biological Engineering at UW-Madison], there has not been an incentive to mass-produce the compound. “The bottleneck in having the fuel ready for prime time is the availability of cost-effective GVL,” he says.

Now that they have demonstrated the process for converting GVL to transportation fuel, Dumesic and his students are developing more efficient methods for making GVL from biomass sources such as wood, corn stover, switchgrass and others. “Once the GVL is made effectively, I think this is an excellent way to convert it to jet fuel,” he says.

[Source: EurekAlert]

Of course, the techniques work at the scale of the lab are a long way from mass production – and for jet fuel, mass – biomass – is the key word. Nevertheless, this represents at least one instance of a technological fix in the waiting for a time when cheap petroleum based jet fuel is no longer available.