VOLATILE liquids burnt as waste at gas fields and coal mines could become a
component of clean “designer fuels”.
Fossil-fuel deposits often contain liquid short-chain hydrocarbons, including
butane and other alkanes. But these hydrocarbons have a low octane rating,
making them less useful as fuel, and also evaporate very easily. So they are
usually flared off, rather than being collected and put to use.
Stephen Paul of Princeton University in New Jersey, whose previous research
has centred on nuclear fusion, realised that these waste hydrocarbons might
still be useful as vehicle fuels if mixed with ethanol—which has a higher
octane rating and evaporates less easily.
Unfortunately, the two substances don’t mix well. But Paul has solved that
problem by adding a third component to the mixture: methyltetrahydrofuran
(MTHF), an ether highly soluble in both ethanol and the short-chain
hydrocarbons.
Advertisement
MTHF can be produced easily by fermenting wastes rich in cellulose or starch,
such as corn husks, straw, sugar-cane waste or paper-mill sludge. Tests show
that exhausts from vehicles powered by Paul’s designer fuel contain up to 50 per
cent less unburnt hydrocarbon, and 20 per cent less carbon monoxide, than those
produced by conventionally fuelled cars.
The fuel, containing ethanol, the short-chain hydrocarbons and MTHF in
roughly equal measures, can be used with “flexible-fuel” engines, designed to
run on conventional petroleum or a mixture of petroleum and ethanol. Paul
demonstrated this by driving a Dodge minivan from Princeton to the Boston
meeting on one tank of the fuel, with enough remaining for his wife to take
their children to local tourist attractions. That’s about the same as the
vehicle achieves on a tank of petroleum, Paul says.
Princeton has licensed the technology to the Pure Energy Corporation of New
York, and in July, the US Department of Energy proposed classing it as an
“alternative fuel” —a move that should encourage its use by companies
operating vehicle fleets.
