The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) said it conducted a trial extraction of rare earths from seabed mud at depths of around 6,000 meters near Minamitorishima Island, south of Japan, on February 1, 2026. Experts worry that the project, though intended to reduce reliance on Chinese rare-earth supplies, faces significant uncertainties regarding technological readiness, cost-effectiveness, and environmental impact.

Japan's deep-sea trial for rare-earth mining carries strategic significance, but it remains constrained by unresolved challenges in technology, cost, and environmental responsibility, said Hu Zhenyu, director of the Department of Sustainable Development and Blue Economy at the China Development Institute.

From a technical perspective, Japan has yet to establish a fully independent deep-sea mining capability. The trial relied on a slurry-pumping system manufactured in the United Kingdom, commonly known as a riser or slurry-lifting pipe. Earlier delays caused by equipment delivery issues exposed vulnerabilities in the project's supply chain. Hu noted that whether the equipment can function reliably under real-world, complex conditions has yet to be demonstrated. 

Economic viability is another major concern. Although waters around Minamitorishima are believed to contain substantial rare-earth resources, Hu said deep-sea mining costs are far higher than those of land-based mining. Rare-earth separation and refinement also pose an even greater challenge, as the processes involve more than 200 complex steps, making efficiency and cost control difficult.

The Day-ichi Life Research Institute estimates that Japan's production costs could be several times, or even dozens of times, higher than those of China's onshore rare-earth operations, largely due to extremely low extraction efficiency – around two kilograms of rare earth elements per tonne of mud.

The upfront investment is heavy and the period of return on investment is long. The equipment investment is estimated at approximately 75 billion yen, with a projected payback period of up to 16 years, according to Hu.

Environmental risks also loom large. According to the Chinese expert, deep-sea mining activities have shown both short-term and long-term effects.  

In the short term, extraction events cause sediment plume pollution and may disrupt benthic ecosystem organisms. Low-frequency noise from mining equipment may interfere with the behavior and migration of marine mammals. 

In the long term, deep-sea mining is widely regarded as posing potentially irreversible threats to fragile ocean ecosystems. Hu warned that deep-sea ecosystems have extremely low resilience and very slow recovery rates. He further noted that disturbances at such depths could lead to the loss of endemic species and the breakdown of ecological balance.

Although Japanese authorities say the trial adheres to self-established environmental monitoring standards, the International Seabed Authority has yet to finalize universal regulations for deep-sea rare-earth mining. Hu said that amid continued concerns from the international scientific community and environmental organizations, any unilateral push to advance such projects would pose not only technical and economic risks but also environmental and ethical implications.

Overall, Japan's deep-sea rare-earth extraction trial remains far from commercially viable, with its future constrained by gaps in technology, economics, and environmental sustainability.