"Flammable ice" or methane hydrates, could be the world's last great source of carbon-based fuel - assuming the methane can be mined from the crystal lattices of ice that trap it beneath ocean beds and permafrost.

A new study that great extinction at the end of the Permian epoch, where at least 90 percent of the planet's plant and animal species were wiped out, could have been caused by a dramatic increase in methane in the atmosphere. The authors caution that current plans for mining methane hydrates from the ocean could release catastrophic levels of methane.

The U.S. has initiated research into a near-limitless energy source that has the potential of ending America?s dependency on foreign fuels but could, if improperly used, cause devastating damage to the environment.

Scientists believe there is a vast and as yet untapped source of energy locked in mud at the bottom of the ocean. They say frozen natural gas produced by deep sea bacteria has built up over thousands of years to provide the huge energy reserve.