Japan examines ways to harvest frozen fuel

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TOKYO -- Like an ice that burns, methane hydrate is cold, white and would light up like a gas stove if held to a flame. So much of the frozen fuel naturally blankets the seabeds off Japan and elsewhere that scientists say it could power the world for centuries.

Yet as soon as researchers plumb the depths and pull the potentially revolutionary energy source to the surface, the frosty crystallized methane starts to fizz and bubble to oblivion as it warms up, gasifies and dissolves into the ocean.

Most countries don't even bother exploring offshore reserves for lack of harvesting technology. But in resource-poor Japan, plucking the deep-sea bounty off its shores is more than science fiction; it is a national initiative Tokyo hopes will become reality by 2015.

"Japan's domestic resources are almost zero, so nonconventional sources are a top priority," said Tetsuo Yonezawa of the methane hydrate research team at the government-backed Japan National Oil Corp. "There is more than 100 years worth of Japanese natural-gas consumption there."

Japan's push heats up in January, when a drilling ship sets sail for the choppy Pacific Ocean off south-central Japan to dig 10 to 20 wells in methane hydrate beds along the Nankai Trough, more than 3,630 feet under water.

Japan hopes to determine by 2011 whether commercial methane hydrate mining is economically feasible and, if so, begin doing it four years later.

Methane hydrate is a crystal structure of methane gas surrounded by water molecules, held together by freezing temperature and crushing pressure. Separating the two yields the methane, or common natural gas, and water.

Knowledge of the substance dates to the 1890s, but it has not caught on as an energy source because it is found in Arctic permafrost and deep-ocean sediments.

Worldwide resources, however, are huge -- 875,000 trillion cubic feet, or about twice as much carbonized energy as worldwide coal, oil and ordinary gas resources combined, estimates show.