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THE stench of petrol at filling stations could soon be a thing of the past,
the ACS heard.

For every litre of petrol that goes into your tank, about a gram of vapour is
released into the air. The hydrocarbons in petrol contribute to ozone and smog,
and its aromatic compounds are suspected carcinogens and in high doses can cause
leukaemia. An additive called methyl-tert-butyl ether (MTBE) adds a
pungent smell to the fumes.

鈥淭here have been reports of feeling unwell after exposure to MTBE, and it has
caused tumours in animal experiments,鈥� says Melinda Henry at the World Health
Organization in Geneva. The WHO doesn鈥檛 recommend limits for petrol vapour
emissions, but to meet local regulations some filling stations in the US and
Germany have fitted vacuum pumps that suck excess vapour and air back into the
filling station鈥檚 tank. However, even the best of these systems still allow a
quarter of the vapour to escape.

Now Klaus Ohlrogge and his colleagues at the government-funded GKSS Research
Centre in Germany have devised a novel way of cutting vapour leakage to less
than 5 per cent. The system works by sucking out 1.5 times as much air as the
volume of fuel being pumped into the car tank, and pumping this air into the
headspace of the filling station鈥檚 storage tank.

When the pressure in this tank is higher than the pressure outside, this
vapour-laden air is funnelled through a stack of membranes coated with a
silicone material that selectively adsorbs hydrocarbons based on their chemical
structure. The adsorbed hydrocarbons diffuse through the membrane coating into a
porous inner layer, pulled by a concentration gradient, from where they are
funnelled back into the station鈥檚 storage tank. The cleaned air is then vented
to the atmosphere.

Nine petrol stations in Germany are trying out the system, and one unit is
being tested in the US.