Gas boom may be mixed blessing for climate change
Coal may be on the way out as a source of energy, but all the hype over its cleaner replacement should come with a climate-change health warning
Thanks to its controversial nature, most people have some knowledge of shale gas and fracking, the method used to extract it.
Methane hydrate is formed naturally when methane gas, produced by microbial action or the effects of earth's heat and pressure on buried organic matter, combines with water at moderate pressures and temperatures ranging from below zero to nearly 25 degrees Celsius. After it is formed, it becomes fairly stable and looks like ice.
About 99 per cent of methane hydrate deposits are found in deep-water environments and 1 per cent occurs on land.
It may be found in nodules and mounds on the seafloor and in spaces such as pores, cracks, and seams within sediment on the seabed that is hundreds of metres thick, as deep as 2,000 metres down. It occurs on land mainly in sediment under thick permafrost in Arctic latitudes in Alaska, Canada, and Russia.
In the US, in the deep sediment of the northern Gulf of Mexico alone, potential methane hydrate resources are estimated to be as large as 605 trillion cubic metres (tcm). A more modest 2.4 tcm is estimated to be present on the Alaskan North Slope in sandy sediment beneath thick permafrost. These two deposits represent a tenfold increase over the US' future natural gas supply as estimated in 2008. Natural gas production in the US in 2008 was about 0.5 tcm, and the extra methane hydrate could potentially extend that supply for another 1,000 years.
New optimism in the US over indigenous natural gas resources thus comes independent of expected advances in fracking that will allow significantly more shale gas to be extracted than is currently possible.