Japan taps methane hydrate from seabed

Sara Reardon, reporter

A burst of flame atop of a Japanese drilling ship today heralded the world's first successful production of gas from frozen methane hydrate at the bottom of the ocean. This slushy substance, made up of methane caged by water molecules, holds 164 times the energy of an equivalent volume of conventional gas. If Japan can harvest its hydrate cache in commercial quantities, the country could eventually become a net energy producer for the first time in its history.

The methane hydrates in the Nankai trough, about 80 kilometres off Japan's southern coast, are estimated to hold enough energy to supply the country's needs for a century. Worldwide, the energy stored in hydrates is greater than all other energy sources combined. A number of countries, including the US and Russia, which have methane hydrate caches offshore and under their permafrost, have begun researching ways to harvest them.

The 2011 Fukushima nuclear disaster, which threw Japan's energy planning into turmoil, spurred its government to fast-track the methane hydrate project. For the current production test, the government-run Japan Oil, Gas and Metals National Corporation first drilled a borehole hole 300 metres into the seabed, about 1000 metres below sea level. Methane hydrates' solid structures are maintained by cold and high pressure, so the researchers break them up into gas and water by pumping seawater out of the borehole to lower the pressure within. The gas then rises up a pipe to the ship.

In the current tests, the gas is being burned off. Today's success in producing a steady flow is promising for future commercial production, which could start as early as 2018. But a number of environmental challenges remain before large-scale extraction could begin. Removing crystallised methane from the sea floor could destabilise the seabed and cause landslides. And if methane escapes from the deep well in the Nankai trough, it will dissolve in the water and acidify the local area, potentially harming ocean life.

Hydrate mining in shallower waters could pose further problems. If methane escapes into the atmosphere, it could contribute to global warming. Measured over a century, methane is 25 times as powerful a greenhouse gas as carbon dioxide.

Source: http://feeds.newscientist.com/c/749/f/10897/s/297e1e04/l/0L0Snewscientist0N0Cblogs0Cshortsharpscience0C20A130C0A30Cjapan0Etaps0Emethane0Ehydrate0Efro0Bhtml0Dcmpid0FRSS0QNSNS0Q20A120EGLOBAL0Qonline0Enews/story01.htm

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