London, September 4 : Chemists have now developed a new way to transport gases like methane and natural gas, by converting them into a powdered form.
According to a report in Nature News, Andrew Cooper and his colleagues at the University of Liverpool, UK, have found that they can trap methane in a bizarre material dubbed 'dry water', a mixture of silica and water that looks and acts like a fine white powder.
The methane reacts with the water to produce a crystalline material called methane gas hydrate, in which individual methane molecules sit inside ice-like cages of water molecules.
In principle, this could offer a way to store methane conveniently for use as a vehicle fuel. Methane-powered vehicles produce less pollution than those running off petroleum fuels.
"It looks like a powder, but if you wipe it on your skin, it smears and feels cold," said Cooper.
Natural gas is mostly methane, and so the new material could even be used as an alternative to pipelines to ship it from gas fields.
Methane gas hydrate forms naturally when water is mixed with methane at high pressure and low temperature.
Huge deposits of the crystalline substance exist in the deep sea, where they could provide vast fuel reserves. But rising global temperatures increase the chances of the hydrate decomposing, releasing the greenhouse gas and accelerating further warming.
This mechanism has been proposed as a cause of dramatic environmental change in the distant past.
Using methane gas hydrate as a kind of 'solid methane' for storage and transport is an idea that might work, according to the researchers.
Cooper and his colleagues convert water to 'dry water' by stirring it up with a special form of silica, called hydrophobic fumed silica.
This consists of tiny grains of silica - the same basic material as sand - coated with a chemical layer that makes them water-repellent. The silica particles cover the surface of water droplets and stop them from coalescing.
The resulting 'dry water' is a very odd substance.
"It looks like a powder, but if you wipe it on your skin, it smears and feels cold as the water is released," said Cooper.
The researchers found that their powder soaks up large quantities of methane at water's normal freezing point, producing crystalline methane gas hydrate within the silica-coated drops.
A litre of methane gas can be stored in about 6 grammes of the material.
This storage capacity, they say, is very close to the target set by the US Department of Energy for such materials, and compares well with that of other candidate storage media.
Crucially, it is made from cheap raw materials, helping to make this method economical relative to other, more exotic potential methane-capture materials such as designed molecular frameworks.