Mining The Ocean Bottom For Metals – Is This A Bad Idea?

Everyone is finally getting the idea that going green isn’t just shutting down coal plants or driving electric vehicles.

Those are necessary, but the how may be even more important than the what. Bringing up green tech like electric vehicles and wind turbines takes a lot of resources, more than we can provide now, particularly special metals like Co, Li, Te and Nd, as well as just base metals like Fe, Cu, Pb and Zn.

And getting those metals out of the ground in the amounts needed is as bad or worse for the environment as drilling for oil and gas, or mining for coal. And China leads the world’s production of these metals – by a lot.

In mineral-rich regions of China, poisoned water and soil have caused skyrocketing disease, cancer and death rates in impoverished villages, like that shown above. As a result of producing things like neodymium (Nd) for wind turbine magnets, most crops and animals have died around a 5-mile-wide crusty lake of toxic black sludge near the City of Baotou.

This toxic wasteland is so large that it’s visible by satellite.

So it was disappointing to see the world moving ahead on mining for some of these metals on the ocean floor.

Geologists have long known that the ocean floor is chock full of metals – Cu, Ni, Ag, Au, Pt and even diamonds.

These occur as sulfide crusts around deep ocean vents, in thin sediment layers and as bits lying on the ocean floor. But the big prize is something called a manganese nodule.

Manganese nodules are polymetallic rock concretions on the sea bottom formed of concentric layers of iron and manganese oxihydroxides. These nodules occur in most oceans, even in some lakes, and are abundant on the abyssal plains of the deep ocean between 4,000 and 6,000 meters (13,000 and 20,000 ft).

Manganese nodules contain varying, but large, amounts of manganese, iron, nickel, copper, cobalt, titanium and barium, as well as lesser, but significant, amounts of precious and rare metals like niobium, vanadium, thallium, bismuth, yttrium, lithium and molybdenum.

Nodule formation is simple. Most metals are dissolved in sea water to some amount. Over time, they can precipitate around a nucleus of some kind on the sea floor - a shark’s tooth, a fragment of shell - around which the nodule grows.

Manganese oxide minerals are key, especially vernadite, todorokite and birnessite. These form naturally in water and in the pore water between the sediment particle. Other metals are incorporated in smaller amounts during their precipitation.

Nodules grow very slowly, millimeters per million years, and environmental conditions must remain stable over this long of a time - a lot of sediment can’t be raining down on them, there must be constant flow of ocean bottom water, small pieces of shells need to be around to serve as nucleation sites, the sediment must be porous, not hard rock, and there must be a good supply of oxygen in order to form the manganese oxides.

Thus, deep ocean abyssal plains are perfect. Areas having high economic supplies are concentrated particularly in the Pacific and Indian Oceans, in the wide deep-sea basins at depths of 3500 to 6500 m.

The Clarion-Clipperton Zone (CCZ) is the largest, about the size of Europe, extending from the west coast of Mexico to Hawaii. The total mass of manganese nodules here is over 21 billion tons. Other important areas include the Peru Basin, the Penrhyn Basin near the Cook Islands, and the central Indian Ocean.

So you might wonder – Who owns these areas?

Uh…no one. These are in international waters, supposedly overseen by the United Nations. But regulations have never been formally established for ocean mining. The UN has a little-known, and little watched, bureaucracy known as the International Seabed Authority (ISA) headquartered in Kingston Harbour, Jamaica.

The ISA kind of goes its own way, receives little oversight and convenes their own general assembly once a year at their headquarters. Delegates from the 168 member countries descend on Kingston from around the world. Their assignment is to try to mitigate the long-term destruction of the ocean floor, not to prevent its mining.

The members choose locations where ocean mining will be permitted, issue licenses to mining companies, and draft the technical and environmental standards of an Underwater Mining Code, waiting for the day when this new thing takes off and parts of the ocean floor look like wet ant colonies. And that day may be this year.

The ISA is already granting “exploratory permits” to dozens of companies, and some of these are for delicate subsea places like the beautiful “Lost City” of underwater hot springs east of Florida, the largest ever discovered. These will be destroyed before anyone is even aware of their existence.

Expected mining rates are thousands of square miles a year and the horrible thing about this whole affair is that, for the most part, we don’t know what’s down there. It’s easy to figure out where the nodules are, but not much else. Like what’s living there.

The nice thing about manganese nodules is they are 99% usable minerals – they’re all metal. So there’s no toxic tailings or mining waste like on land.

Regular ores are mostly not metal. A 20% metal ore is a huge yield. Often they are less than 2%. This means that large amounts of mining wastes are generated, even before processing begins.

Another positive for nodules is no deforestation, no open pits, no contaminated rivers or aquifers, no tailings impoundments, and no exploitation of indigenous peoples. Certainly there will be no child labor as occurs in mining areas in sub-Saharan Africa.

But one thing Nature has taught us is there’s no such thing as a free lunch.

The individual nodules lie loosely on the sea floor or buried shallowly in the sediment. They can be harvested from the sea floor bottom with underwater vehicles similar to a potato harvester, but that might be too slow for industry.

According to WorldOceanReview, the scientific community agrees that mining manganese nodules would create a dire threat on the marine habitat, even those not in the mining area.

All organisms that can’t escape quickly enough are killed, including snails, sea cucumbers and deep sea worms, a huge part of the seabed food chain. The mining stirs up enormous amounts of sediment that are moved by ocean currents through and out of the area, to settle down on the sea floor again, covering sensitive organisms, particularly the sessile, or immobile ones, which then die.

Not might die, will die. Nothing like these sediment clouds have hit these organisms in a million years. They can’t handle it.

The mining, pumping and cleaning of the manganese nodules creates noise and vibrations, which disturb marine mammals such as dolphins and whales, and could force them to flee from their natural areas to die from not having their natural food supply.

The sediment-laden water produced on the ships by the cleaning of manganese nodules will be released back into the sea, creating another sediment cloud. We should release the sediment near the sea bottom instead of letting it fall through the entire water column killing everything on its way, particularly algae and plankton, but that would require miles of very wide tubing at high cost.

So the talk at ISA is how to reduce these problems as much as possible, admitting they can’t be eliminated. The ISA requires environmentally sound methods and solutions, which are possible. We can reduce the sediment cloud by using a cowled rather than an open harvesting machine.

Scientists in the German project Disturbance and Recolonization (DISCOL) ploughed up a sea-floor area of several square kilometers in the Pacific and observed that it took seven years for the sea bottom life to basically recover. Of course, many species disappeared permanently.

But destruction increases proportionally with the area, especially since recolonization occurs from the edges, so scaling up from several square kilometers in the above experiment to a million square kilometers indicates massive, long-term destruction.

Fortunately, the ISA plans that the licensed areas not be harvested all at once, but in small steps. Small harvested sites should be surrounded by large undisturbed areas for rapid recolonization. Marine biologists are determining what the patterns of mined and undisturbed areas should look like.

Sounds great if it can be agreed upon. And followed. No one will be down there looking, and the sea cucumbers won’t be able to tell us.