Seabed Nodules and Rare Earth Elements

Manganese nodules, about the size of potatoes, litter the deep-water seabed. Sometimes they are so abundant that they cover 70% of the seabed surface. They have been tantalizing potential miners for decades, and now they are suddenly back in play.

Manganese nodules at 5000m in the South Pacific (teara.govt.nz)

A nodule grows slowly, adding about 1cm to its diameter over the course of several million years. It grows around a core – a tiny fragment of shell or sand – with concentric layers of iron and manganese hydroxides, along with copper, nickel and cobalt oxides, precipitating from the water around it, reaching 5-10cm in diameter. Most of the nodules lie on the abyssal plains, 4000-6000m deep.

A manganese module split in half (nytimes.com).

The Challenger expedition of 1872 first dragged some up. Serious efforts to try to exploit them didn’t occur until the 1970s and 1980s, but the practical, economic and political problems were just too great to resolve.

For problems there are. For instance, who do the nodules belong to? Because they lie mostly in deep water, beyond the 200 mile limits of Exclusive Ecological Zones, the UN Law of the Sea eventually established that they are the Common Heritage of Mankind: whoever succeeds in mining them will have to share the profits with the rest of the world. Not exactly an attractive prospect for profit-oriented corporations.

Besides the question of who owns the nodules, and the taxes that will accompany any deep seabed mining venture, how do we get them to the surface? No one yet has a particularly good idea. Imagine trying to control a vacuum cleaner with a hose a few km long.

The biggest problem, though, is that, pure as the nodules might be, there are land-based sources of manganese, iron, copper and nickel where the costs of mining the ore have remained much less than any estimated for retrieving nodules from such deep water.

So nothing much has happened.

Until now. Since a publication in 1968, we have known that the nodules also contain low levels of Rare Earth Elements (REEs), and very recently Rare Earth Elements have caught everyone’s attention. They are the elements that are piled up in a ‘pull-out’ near the bottom of the Periodic Table with unfamiliar names such as Cerium, Dysprosium, Yttrium, and Lanthanium.

The 16 Rare Earth Elements on the Periodic Table (pubs. usgs.gov)

Modern technology can’t do without Rare Earth Elements. We use them increasingly in magnets, lasers, fiber optics, disc drives, memory chips, superconductors, liquid crystal displays, rechargeable batteries, smart phones, smart bombs. The magnets of green technologies of wind turbines and hybrid cars depend on them.

The 16 Rare Earth Elements aren’t actually rare, they just rarely occur in economically exploitable ore pockets. China now has 95% of world production, acquired through its familiar combination of low labor costs and particularly lax regulation of the environmental hazards – which include strip mining, acidification of watersheds, creation of toxic reservoirs, and accumulation of radioactive sludge. A reminder that our potentially green economy is currently dependent on very dirty mineral extraction.

China's monopoly is a recent development (pubs.usgs.gov)

Rare Earth mineral mining in China - strip mining, acid reservoirs, radioactive thorium accumulation (

And then a couple of months ago, China stopped shipment of REEs when Japan arrested one of its fishing vessels. The five week embargo caught the world’s attention. Though China eventually lifted the embargo, it says it needs most of what it produces its for own uses, and has told other countries to mine their own REEs, or move their companies to China.

So everyone is now looking at other sources of REEs. Companies are emerging in California, Greenland, Australia, Canada, South Africa and unfortunately Congo Republic to mine them, but it will still be about 10 years before the dependency on China will be broken.

And that brings us back to the seabed nodules. The value of their common minerals has been increasing, and now their REEs have become very attractive as well. Soon, despite the problems of profit sharing and accessibility, a new seabed mining industry will develop.

Competitive, high seas, deepwater seabed vacuuming. What could go wrong with that?

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