Japan to mine rare earths from ocean floor

Japan has announced a successful attempt to mine rare earths, which are critical for high-tech manufacturing, from the depths of the Pacific Ocean. While the discovery is promising, significant obstacles remain before commercial exploitation can begin.

The Japanese government’s Strategic Innovation Promotion Program (SIP) has brought up seabed mud containing valuable elements such as yttrium and dysprosium from a depth of 5.6 kilometers near the island of Minamitorishima.

The mud found was exceptionally rich in medium and heavy rare earths, which are considered more valuable than lighter elements. They are widely used in electric cars, robots, radars and the aerospace industry. China controls the majority of the global supply of these elements.

According to the SIP report, medium and heavy rare earths made up about 54% of the mud mined. The most abundant element found was yttrium (29.9%), which is used in chip manufacturing and the defense industry. The mud also contained gadolinium (4.9%), which is used in nuclear reactor control rods, and dysprosium (4.6%), which is added to electric car motor magnets to improve their performance. Neodymium, another light rare earth metal important in magnet production, was also found at 18.9%.

Toru Okabe, a professor of resource technology at the University of Tokyo, said the mud’s properties are similar to those of ion-adsorption deposits, which have been widely developed in southern China and are also found in Vietnam and Myanmar.

Acquiring the equipment and ships needed to mine rare earths near Minamitorishima is extremely expensive. In a recent test, the research vessel Chikyu connected nearly 600 ten-meter pipes, lowered them to a depth of 5,600 meters to the seabed, and pumped the muddy water to the surface.

The larger trial, which will begin in February next year, will involve airlifts to exchange personnel and the separation of water from the mud at a factory to be built on the island. The plan is to confirm a mining capacity of 350 tons per day, but Japan's economy ministry estimates that profitability will only begin at 3,500 tons per day.

Nikkei Asia estimates that extracting rare earths from the seabed would require an investment of about 340 billion yen ($2.08 billion). After extraction, the elements must be separated and refined, which is also an expensive process. Unlike many terrestrial deposits, the mud at Minamitorishima was found to contain almost no radioactive or other harmful substances, reducing the environmental impact.

Professor Okabe, however, remained skeptical. He said the project was "academically important, but not a very realistic means of ensuring resource security when considering the cost-effectiveness."