Rare earth deposits sufficient to meet global demand for centuries have been found in Japan’s exclusive economic zone (EEZ) near one of the Ogasawara islands some 2,000 kilometers southeast of mainland Tokyo.

The discovery was announced by a research team led by the University of Tokyo and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in an article published in the online U.K. journal Scientific Reports on April 10.

Some 90 percent of the world’s supply of rare earths, used in the manufacture of advanced electronics, is currently produced by China. In 2013, the Japanese research team found rare earth-rich mud on the seafloor off Minamitorishima island, part of the Ogasawara island group. Between then and 2015, a research vessel took samples from 25 sites on the ocean bottom about 5,600 meters below the surface, approximately 250 kilometers south of Minamitorishima, and estimated the amount of rare earth deposits across about 2,400 square kilometers.

The team estimates there are about 16 million metric tons of rare earths in the survey area, including enough terbium (used in motors) to last 420 years, and enough europium (used in the luminescent component of liquid crystal displays) for 620 years.

The researchers also developed extraction technology. Taking into account that the rare earth granules in the mud are at least four times the diameter of usual mud grains, the team invented a technique to sift out the valuable materials with a special machine. Tests on land showed the sifting yielded mud with rare earth concentrations 2.6 times higher than just scooping up unsifted mud.

“We found that there are enough (rare earth) resources on the sea bottom,” said team member and University of Tokyo professor Yasuhiro Kato. “The possibility of extracting them efficiently is rising, and we are one step closer to making development of this resource a reality.”

(Japanese original by Yui Shuzo, Science and Environment News Department)