According to Wikipedia, Methane clathrate, also called methane hydrate or methane ice, is a solid form of water that contains a large amount of methane within its crystal structure. Originally thought to occur only in the outer regions of the Solar System where temperatures are low and water ice is common, significant deposits of methane clathrate have been found under sediments on the ocean floors of Earth.

Natural gas locked up in water crystals could be a source of enormous amounts of energy – and if a new technology delivers what scientists are claiming, then it could even be emissions-free too. US Scientists have revealed how natural gas locked up in frozen water crystals could provide massive amounts of energy, and claim that it could even be totally emissions-free. The claim was made by Tim Collett of the USGS at the national meeting of the American Chemical Society. He told the crowd that clathrate hydrate (CH) looks like everyday ice but, as well as being partly made of water, the molecules are also organized into “cages”, which trap individual molecules of methane.
Compared to other fossil fuels, methane – also known as natural gas – releases less carbon dioxide per unit of energy generated. Nevertheless, burning it still releases carbon dioxide and thus drives climate change.

Due to their physical structure, clathrate hydrate cages "prefer" to have carbon dioxide at their cores, so if carbon dioxide is pumped into the hydrate, it spontaneously takes the methane's place. As a result, it should be possible to simultaneously extract methane and store carbon dioxide. Remarkably, a new method of extracting the methane and ’swapping’ it with carbon dioxide could turn the substance into a revolutionary carbon-neutral fossil fuel.

Previous attempts to obtain methane by heating up the hydrate were not effective, but pumping fluids out of the hydrate to release the pressure does release the methane.The US Department of Energy is now working with the oil company ConocoPhillips on a field trial in Alaska, to test whether the technique can be scaled up. According to Ray Boswell of the US National Energy Technology Laboratory, “A lot of countries are getting very serious about this. Something that used to be more hype than reality is becoming something people are seriously talking about.”