The site of the trials in Nagaoka (Research Institute of Innovative Technology for the Earth)
Interest in sub-seabed storage - a method of sealing carbon dioxide (CO
2) under the seabed - has been growing. Atmospheric carbon dioxide is believed to be the principal cause of global warming, and the underground sequestration of the gas is regarded as a very promising method for reducing carbon dioxide emissions, which is considered one of the most vital environmental issues facing humankind.
Two Trillion Tons Worldwide
Injecting carbon dioxide into the ground is a technology currently used for the subterranean storage of natural gas and for increasing petroleum production - known as "enhanced oil recovery," or EOR. The idea behind sub-seabed storage is to apply this technology in the interests of environmental conservation.
Sub-seabed storage of carbon dioxide involves capturing the gases emitted by fossil-fuel-burning power stations and large factories and other industrial facilities, and then separating out the carbon dioxide while still in gaseous form. This is then transported by tankers or pipelines to the sea, where it is injected under pressure into the aquifer layer - a layer of water-containing permeable rock over 1,000 meters below the seabed.
Work on the trial (Research Institute of Innovative Technology for the Earth)
Above the aquifer stratum is a layer of impermeable rock called caprock. This acts as a lid on the aquifer, and it is thought that large quantities of carbon dioxide could be sequestered in the aquifer layer for a long period without escaping. Research is currently under way in Japan, Europe, and the United States on capturing carbon dioxide in this way, not only under the sea but also deep under land. Some researchers believe that as much as 2 trillion tons of carbon dioxide could be sequestered in this way.
Japan's Wealth of Experience
It is estimated that up to 90 billion tons of carbon dioxide can be stored in subterranean locations in Japan and sub-seabed locations in Japanese waters. This corresponds to 70 to 80 years' worth of Japanese carbon dioxide emissions. As Japan has a wealth of experience and know-how in underground storage of natural gas and EOR technology, its work in the field of carbon dioxide sequestration is thought to be closest to practical application.
In 2003 the Research Institute of Innovative Technology for the Earth (RITE) started trials of injecting carbon dioxide into the aquifer layer at a depth of 1,100 meters in Nagaoka, Niigata Prefecture. This was the first time that trials of this technology as a means of carbon dioxide sequestration had been undertaken in Japan. In 2005, researchers successfully injected 10,000 tons of carbon dioxide. The major earthquake that struck the Chuetsu area of Niigata Prefecture in October 2004, measuring magnitude 6.8 on the Richter scale, had no effect on the carbon dioxide that had been stored up to that time. In the light of this, the trials of this technology were continued.
In the words of Murai Shigeo, the leader of the RITE carbon dioxide sequestration group: "We have been able to show that carbon dioxide injection in Japan's particular geological conditions is possible, and computer simulations based on our monitoring activity give a good idea of how the gas will behave over the next thousand years."
The parties to the 1996 protocol to the London Convention (Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, 1972) recently approved carbon dioxide disposal into sub-seabed geological formations. In the light of this, the Japanese government has indicated its intention to amend the Law Relating to the Prevention of Marine Pollution and Maritime Disaster and introduce the necessary ordinances to facilitate carbon dioxide sequestration as a means of combating climate change.
http://web-japan.org/trends/science/sci070202.html
