TOKYO — Japan said Tuesday that it had extracted gas from offshore deposits of methane hydrate — sometimes called “flammable ice” — a breakthrough that officials and experts said could be a step toward tapping a promising but still little-understood energy source.  The gas, whose extraction from the undersea hydrate was thought to be a world first, could provide an alternative source of energy to known oil and gas reserves. That could be crucial especially for Japan, which is the world’s biggest importer of liquefied natural gas and is engaged in an anguished public debate about whether to resume the country’s heavy reliance on nuclear power.  Experts estimate that the carbon found in gas hydrates worldwide totals at least twice the amount of carbon in all of the earth’s other fossil fuels, making it a potential game-changer for energy-poor countries like Japan. The exact properties of undersea hydrates and how they might affect the environment are still poorly understood, however, as is the potential for making extraction commercially viable.  Japan has invested hundreds of millions of dollars since the early 2000s to explore offshore methane hydrate reserves in both the Pacific and the Sea of Japan. That task has become all the more pressing after the Fukushima nuclear crisis, which has all but halted Japan’s nuclear energy program and caused a sharp increase in the country’s fossil fuel imports.  The Japanese Ministry of Economy, Trade and Industry said a team aboard the scientific drilling ship Chikyu had started a trial extraction of gas from a layer of methane hydrates about 300 meters, or 1,000 feet, below the seabed Tuesday morning. The ship has been drilling since January in an area of the Pacific about 1,000 meters deep and 80 kilometers, or 50 miles, south of the Atsumi Peninsula in central Japan.  Using a specialized drill, the team converted the undersea methane hydrate into ice and natural gas, and brought the natural gas to the surface, the ministry said in a statement.  Hours later, a flare on the ship’s stern showed gas was being produced, the ministry said.  “Japan could finally have an energy source to call its own,” said Takami Kawatomo, a spokesman for the Japan Oil, Gas & Metals National Corp., or Jogmec, the state-run company leading the trial extraction.  The team will continue the trial extraction for about two weeks before analyzing how much gas has been produced, Jogmec said. Japan hopes to make the extraction technology commercially viable in about five years.  “This is the world’s first trial production of gas from oceanic methane hydrates, and I hope we will be able to confirm stable gas production,” Toshimitsu Motegi, the Japanese trade minister, said at a news conference in Tokyo. He acknowledged that extraction still faced unknowns and technical hurdles.  Still, “shale gas was considered technologically difficult to extract but is now produced on a large scale,” he said. “By tackling these challenges one by one, we could soon start tapping the resources that surround Japan.”  Jogmec estimates that the surrounding area in the Nankai submarine trough holds at least 1.1 trillion cubic meters, or 40 trillion cubic feet, of methane hydrate, enough to meet 11 years’ worth of gas imports to Japan.  A separate, rough estimate by the National Institute of Advanced Industrial Science and Technology has put the total amount of methane hydrate in Japanese waters at more than 7 trillion cubic meters, or what researchers say is closer to 100 years’ worth of Japan’s natural gas needs.  “Now we know that extraction is possible,” said Mikio Satoh, a senior researcher in marine geology at the institute who was not involved in the Nankai trough expedition. “The next step is to see how far Japan can get costs down to make the technology economically viable.”  Sometimes referred to as “flammable ice,” methane hydrate is a sherbet-like substance that can form when methane gas is trapped in ice below the seabed or underground. Japan, together with Canada, has already succeeded in extracting gas from methane hydrate trapped in permafrost soil.  Experts say there are abundant deposits of gas hydrates in the seabed and in Arctic regions. According to the U.S. Geological Survey, recent mapping off the North Carolina and South Carolina coasts show large accumulations of methane hydrates. Canada, China, Norway and the United States are also exploring hydrate deposits.  Scientists at the U.S.G.S. note, however, that there is still a limited understanding of how drilling for hydrates might affect the environment, particularly the possible release of methane, a greenhouse gas, into the atmosphere, and are calling for continued research and monitoring.  “Gas hydrates have always been seen as a potentially vast energy source, but the question was: How do we extract gas from under the ocean?” said Ryo Matsumoto, a professor in geology at Tokyo’s Meiji University, who has led research into Japan’s hydrate deposits. “Now we’ve cleared one big hurdle.”
If the extraction process is successful, it could provide enough energy to meet the countryâs gas consumption needs for 14 years, experts say.