Deep-sea mining: Why it is time to sink this ship

A recent scientific discovery of polymetallic nodules producing “dark oxygen” at the bottom of the Pacific Ocean provides another reason why deep sea mining shouldn’t be allowed

This July, a scientific paper in Nature announced an extraordinary discovery. On the sea-bed of the Pacific Ocean’s Clarion-Clipperton Zone, 13,000 feet below the sea’s surface, far beyond the reaches of sunlight, said the paper, metallic lumps have been splitting seawater to produce oxygen.

The paper hit headlines in no time. Until now, it has been assumed that photosynthesis — first by tiny microorganisms known as the archaeans and then by plants and trees — produced the oxygen in the earth’s atmosphere. Some of this oxygen, it was also thought, diffuses into oceans’ surface waters. And that, a part of it sinks down, all the way to the sea-bed, supporting life there.

The paper in Nature, titled “Evidence of dark oxygen production at the abyssal seafloor”, challenged each of these notions. Its authors had found higher oxygen levels — not lower — as they got closer to the seabed. Lab tests revealed micro-organisms were not at play, nor were geological or environmental factors. Instead, they found, oxygen is being produced by the lumps — or, as they are more formally known — polymetallic nodules.

The precise mechanics here are yet unknown. It’s conjectured that these nodules get charged as they grow, depositing different metals — like manganese and cobalt — irregularly over time. This creates a gradient in charge between each layer that results in electrical potential, which splits seawater to oxygen.

As discoveries go, this one raises large questions. Some of them, scientific — about the origins of life on the earth; and the deep sea ecosystems supported by the nodules. Others are more ecological in their scope. Given the new discovery, should these nodules be mined?

The nodules are in demand

The world is, as we know, in the throes of an renewables revolution and needs, among other things, critical minerals like lithium, cobalt and manganese.

Most on-shore reserves of these minerals, however, are controlled by China. And so, the idea of deep sea mining for critical minerals — which seeks to pluck these polymetallic nodules from the seabed — has been doing the rounds.

A clutch of countries and companies, as this page shows, are vying to harvest these nodules. 

The construct here is familiar. The industry’s pronouncements are bullish. Take The Metal Company, probably the most high-profile deep-sea mining startup right now. According to its website, its seabed concession with the Republic of Nauru, potentially contains “enough metal to… supply battery metals for 140 million electric vehicles.” Between them, says the firm, its three concessions have “in situ quantities of these metals in quantities equivalent to the requirements for 280 million EVs, roughly the size of the entire US passenger vehicle fleet on the road today.”

The firm also insists that deep-sea mining is superior to land-based mining. “Unlike land ores, nodules do not contain toxic levels of heavy elements, and producing metals from nodules has the potential for us to productize nearly 100% of nodule mass and design a metallurgical flowsheet that generates no tailings and leaves nearly no solid waste streams behind.”

Nor is there, says its website, any accompanying deforestation. In all, it says, “polymetallic nodules are the cleanest path toward electric vehicles.”

These claims, however, have been challenged by critics of deep-sea mining. They claim firms might strip-mine seabeds, disturbing seafloor sediments, killing the species and the poorly understood ecosystems living in or on that layer of soil — with poorly understood fallouts for marine food webs, while potentially releasing the carbon stored in ocean sediments.

That is where things stood till July, when Nature published the paper, and challenged the assumption that polymetallic nodules are inert rocks lying on the seabed. 

In reality, it said, they perform a core ecological function on the seabed.

A deeper question about impact

To survive, life needs energy. Much of the world we see around us lives off photosynthesis. Another world, the ancient one of the archaeans, can still be seen near hydrothermal vents.

Until now, it was thought that life could exist only in places that have photosynthesis or these vents.

The nodules change that. Their discovery suggests a third ecosystem, one which lives off the oxygen produced by these nodules. Even before the paper, these ecosystems were poorly understood. As much as 60% of deep-sea DNA sequence variants have not been placed in any known higher-level grouping, says Discover, the online magazine of the Natural History Museum. “The unknown DNA could represent entire lineages of marine life that have yet to be described.” Some of these lineages, it also adds, were found to be associated with the biological carbon pump, which transports vast amounts of atmospheric carbon in the deep sea. As these organisms die and sink to the bottom of the ocean, they take the carbon with them. This can be preserved permanently in the deep sea sediment, or eventually returned to the upper ocean. “Some of the unknown taxa seem to be involved in this process,” says the article.
The role of the nodules in supporting these taxa now needs to be understood. In the meantime, can our species risk deep sea mining?

Firms like The Metal Company say deep-sea mining poses minimal risks to the seafloor. All it will do, says its website, is “lift polymetallic nodules to the surface, take them to shore, and process them with near-zero solid waste, no tailings or deforestation, and with careful attention not to harm the integrity of the deep-ocean ecosystem.”

As this paper on the website of the International Seabed Authority says, deep-sea mining has made large progress in mining technology. In the seventies, the industry relied on suction dredges lowered to the sea bed to vacuum up nodules. The disturbance to sea floor sediments can be imagined.

That approach has since been junked in favour of more autonomous bottom collectors — vehicles that walk over the sea-bed collecting nodules. Other startups, like Impossible Metals, have created collectors that hover above the seafloor and pick up nodules through robotic arms.

These approaches, however, come with their own questions. Seabeds will get damaged as caterpillar-tracked vehicles range across it. And then, there is the de-oxygenating impact of nodule mining on the seafloor ecosystem. Even in the case of Impossible Metals, the latter point remains. 

For now, The Metals Company has disputed the Nature paper. For its part, Impossible Metals says its “image-sensing technology will identify megafauna present on the nodules and leave those nodules untouched, preserving nodule-dependent fauna.”

Its response raises yet more questions. What about smaller species? 

Just as consequentially, deep-sea miners are not working in an uncrowded market. They are competing not just amongst themselves, but also with on-land miners and critical mineral recyclers.

In such a landscape, the deep-sea miner, who can hoover up the most nodules at the lowest cost, will enjoy competitive advantage. This suggests a race to the bottom. Even that firm, however, might struggle to compete against open mines in Africa and elsewhere. Recall Cobalt Red and the opencast mines of the Congo it describes.

The Draft Red Herring Prospectus of The Metals Company alludes to this risk. “The battery metals production industry is capital intensive and competitive…. Chinese resources firms have… been able to produce minerals and/or process metals from land-based operations at relatively low costs due to domestic economic and regulatory factors, including less stringent environmental and governmental regulations and lower labour and benefit costs.”

Compounding matters, critical mineral prices are falling as battery makers innovate to reduce their dependance on rare minerals. Almost half of Tesla EVs produced in Q1 2022, for instance, had no nickel or cobalt in the batteries. Along the way, Nickel’s price has, as SP Global reported,  “dropped 42.1% since the beginning of 2023, from $29,886/t on Jan. 2, 2023, to $17,290/t as of March 19.” On 6 February, its price also hit a three-year low of $15,660/t. For their part, The Metal Company and Impossible Metals said they would be viable even with Nickel prices below $10,000/t.

And yet, as this essay in Nautilus says, oceanic exploration is expensive — and often goes over budget. In this case, as private equity investor Victor Vescovo told Nautilus, miners will be operating complex machinery in corrosive salt water at near-freezing temperatures under thousands of pounds of pressure per square inch.

Add the costs of ecological restoration — the world really needs to stop seeing ecological damage as an externality — and effective costs climb higher yet. “One estimate suggests that it would cost $75 million to restore one hectare of seabed in the Darwin Mounds in the Northeast Atlantic,” writes ScienceDirect. 

Finally, a regulatory code for overseeing deep-sea mining is not in place. The International Seabed Authority, a UN-affiliated body, is facing charges of election fraud — and accusations that it wants to allow mining even before environmental standards are finalised — as early as this year.

In all, fundamental questions remain unanswered. Should the world focus on developing deep-sea mining — the last frontier unsoiled by our species — or invest in technologies that do not need rare elements. 

The ways of the world

There is irony here. 

We have found out about the nodules around the same time we are looking to destroy them.
As things stand, Andrew Sweetman, a microbiologist who is the lead author of the Nature essay, made his breakthrough after a visit to the Clarion-Clipperton Zone on an environmental survey sponsored by The Metals Company. 

We have been here before. Scientists warned about the risks from smoking but were pushed aside by Big Tobacco. They spoke about the perils of excessive emissions — but were marginalised by Big Oil and Big Coal. Closer home, ecologists have warned about pell mell infrastructure building in the Himalayas, to take one instance, or against building on floodplains, to take another instance, but were brushed aside as well.

What will happen with the nodules? Unlike climate change, where Big Oil actively suppressed information about the greenhouse effect, we know more about the nodules and their importance. At the same time, deep-sea mining is nowhere as influential an industry as big tobacco or oil. The industry is still in an experimental phase. In 2020, it was worth $650 million. In comparison, the oil industry was valued at $6,705 billion in 2023.

So can it get its way? If the experience of geo-engineering and small and modular reactors is anything to go by, even firms positing risky solutions can get support from states and investors.
The first is susceptible to anything that promises to reduce its problems. As for the second, given multi-stage funding, they can cash out well before the larger costs are felt — or the viability itself is established.

It makes one think. Profits — and markets — alone cannot fix the climate crisis. Multilateral governance has to step in.

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M Rajshekhar

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