The Yomiuri Shimbun
The following is the second installment of "Living on an island arc," part of a series of articles examining ways to restore Japan's vitality after the March 11, 2011, disaster. This section examines ways of turning Japan's weak points into strengths.
Japan's island-arc shape helped power the nation's industries with a type of high-quality ore more than 100 years ago, and efforts are under way today to use the volcanic characteristics of the archipelago to re-create this "kuroko" (black ore) on the seafloor.
Kuroko, named after its color, was originally created from the activities of seafloor volcanoes when the Japanese archipelago was created.
Japanese kuroko was of extremely high quality, and ore containing zinc, lead, copper and other metals was mined from the Sea of Japan from the latter half of the Edo period (1603-1867) to the Showa era (1926-1989).
This natural resource is peculiar to island arcs--volcanic archipelagoes parallel to and near the boundary of two converging tectonic plates--and is known as kuroko overseas, as well.
Although Japan's kuroko mines closed after the resource became largely depleted, seafloor volcanic activity similar to that which formed the Japanese archipelago is still going on under the surrounding sea.
The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) focused on this when it began investigating the possibility of creating one of the world's largest kuroko deposits on the seabed about 1,000 meters deep northwest of Okinawa Prefecture.
Strata in the region contain large quantities of hydrothermal water that contains gold, minor metals and other elements that are heated by magma.
JAMSTEC's team, led by senior research fellow Ken Takai, drilled into the seabed using the deep sea drilling vessel Chikyu and buried metal pipes from which hot water could well up.
Metals in the hydrothermal water cooled when they emerged from the pipes and reacted with sea water. The metals slowly settled around the pipes in chimney-shaped kuroko chunks. Natural kuroko deposits take years to form, but the team was able to create 11-meter-tall chunks in only 10 months.
The method was a world first, and JAMSTEC has applied for it to be patented.
Looking for a different type of mineral resource, a team of researchers led by Prof. Yasuhiro Kato of the University of Tokyo's School of Engineering analyzed samples of deep-sea mud collected during deep-sea drilling in the Pacific Ocean last year.
Their study revealed reserves of rare earth elements in quantities 800 times larger than aboveground stores in the deep seafloor in vast areas of the Pacific Ocean, including the Hawaiian Islands and Tahiti.
However, since the mud containing the rare earths is under international waters, mining would require registering the claims with an international organization. The potential cost involved in extracting the rare earths is also unknown.
Nevertheless, such achievements could be advantageous to Japan, which aims to be an ocean-oriented power. A new and significant rare earth find could put the brakes on the recent surge in prices due to China's dominance in production and its export restrictions.
"Japan needs to quickly find out exactly how large the deep-sea rare earth reserves are, figure out how to extract and refine them, and come up with a workable strategy," Kato said.
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Next-generation fuel resource
Methane hydrate, known as "burning ice," has been ramping up expectations as a possible next-generation fossil fuel.
Methane hydrate exists in a solid state in low-temperature, high-pressure environments like the seafloor. Mainly composed of methane and water, this substance could be used as natural gas if it could be exploited.
Japan is leaps and bounds ahead in the race to utilize methane hydrate. In February, the world's first underwater production trial started off Aichi Prefecture. The trial is being conducted by Japan Oil, Gas and Metals National Corporation (JOGMEC), consigned by the government.
JOGMEC has drilled wells for measurement and mining, and plans to start production of methane gas early next year.
If full-scale underwater production near Japan become a reality, gas could be directly supplied to domestic facilities via pipelines.
Scientists estimate the methane hydrate reserve in the sea area from off Shizuoka Prefecture to Wakayama Prefecture is equivalent to about 11 years' worth of liquefied natural gas imports.
More exploration in other areas could lead to more large methane hydrate finds. But again, the major problems are the time and money involved in developing the mining technology and extracting the fuel. Although the government has stated it aims to establish technology for commercial use by fiscal 2018, actual commercial production would take longer.
The government hopes to lower the mining costs by utilizing existing technologies, such as those used in oil drilling, and other means.
JOGMEC successfully achieved continuous production, considered essential for commercial operations, in a ground production experiment in Canada in fiscal 2007 and 2008. In the trial run, 13,000 cubic meters of gas was produced in six days.
Next, JOGMEC hopes to achieve continuous production for several weeks in a deep-sea experiment next year. Success in this trial would be a major step toward commercial production, and Japan's production methods could become the global standard.
"We have methane hydrate reserves close to Japan, which is very significant. We need to succeed in underwater production to pave the way for using this resource," said Yoshihiro Nakatsuka, deputy head of JOGMEC's methane hydrate development division.
(Jul. 11, 2012)
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