Methane hydrates – or “fire ice” – could be key to meeting global demand for fuel when oil supplies run out.
But while they are being touted as a huge potential asset today, the same substance is believed by many to have caused a mass extinction of life on Earth about 55million years ago.
They are frozen water molecules that trap methane gas in a crystalline, lattice-like structure. CO2 hydrates exist on Mars, while on Earth most are filled with methane.
Unlike normal ice, if you light a match to the hydrate it would go up in flames.
Massive untouched reservoirs of fire ice lie deep underwater or under permafrost – and under pressure 23 times that of normal atmosphere.
The US government says the energy in methane hydrates “is immense, possibly exceeding the combined energy content of all other known fossil fuels”.
Extracting the gas is a very complex process, but the US and Japan are conducting advanced drilling tests and are preparing for commercial production.
Environmentalists are concerned about burning more earth-locked hydrocarbons, while some scientists fear large-scale extraction could cause a massive undersea landslide that could trigger a major methane hydrate release.
About 55million years ago, the world’s climate is believed to have changed catastrophically when volcanoes melted natural gas frozen in the seabed, triggering a sudden release of methane hydrates.
But other experts believe harmful CO2 could be injected into the hydrates when the methane is extracted, potentially helping to tackle climate change by cutting emissions.