London, April 24 : Methane hydrate, more popularly known as 'flammable ice', could turn out to be the world's last great source of carbon-based fuel, if it is mined properly.

Methane hydrates are crystal lattices of ice that trap methane beneath ocean beds and permafrost.

According to a report in New Scientist, one problem with extracting this methane is that you have to melt the ice to bring the gas to the surface.

In 2002, a team of geologists from Canada and Japan tried injecting hot water into the ice beneath the delta of the McKenzie river in northern Canada. While this released some hydrates, it used a lot of energy.

Now the same group has extracted methane much more efficiently, and without hot water, by pumping air out of drill holes in the frozen structures. This reduced the pressure, and so raised the melting temperature of the ice so the methane could be removed.

The state-owned Japan Oil, Gas and Metals National Corporation, which announced the test results, wants to extract the 7 trillion tonnes of methane thought to be trapped in hydrates in Japanese coastal waters.

It hopes this will be the answer to Japan's century-long search for an indigenous source of fuel.

ANI