In September 2017, an operation in the East China Sea changed mining forever. Tapping a geological feature called a ‘hydrothermal vent’ – a crack in the ocean bed that spews magma and minerals up from the earth’s crust – the Japan Oil, Gas and Metals National Corporation (JOGMEC) was the first organisation to carry out large-scale mining operations in this way. From an economic perspective, the scheme went well: JOGMEC deployed excavators to capture ore at a depth of around 1,600m, while officials argued they’d secured enough zinc to fulfil Japan’s national consumption for an entire year.

With such wealth beneath the seas, other pioneers have unsurprisingly followed the Japanese example. From Madagascar to Norway, mining vessels have been busy hunting for ores and perfecting extraction techniques, with research by UC Santa Barbara suggesting that dozens of such missions have occurred over the past decade. And why not? In terms of mineral quantities alone, the numbers are astounding. According to one recent study, there is $150tn worth of gold under our oceans – or nine pounds for every single person on the planet. Across the sector more broadly, Global Mining Review suggests annual compound growth could soon reach 37.1%. Not, of course, that the future of deep-sea mining is simply a matter of profit margins. Even before JOGMEC’s landmark expedition, scientists and environmentalists were warning of the serious consequences of the sector to the ocean and its fauna – hardly surprising to anyone who’s seen how mining can ravage landscapes on dry land. No wonder, moreover, that battles over regulations continue apace, with companies and nation-states in disagreement over how fast to embrace the deep-sea revolution. More than that, critics argue that deep-sea mining is fundamentally unnecessary. Countering the widespread assumption that rare minerals are vital to industrial life in general and the green revolution in particular, they instead suggest that humanity can find other ways to save the planet – while leaving the oceans well alone.

Down to the depths

Scientists have known about the theoretical potential of deep-sea mining for generations. In Jules Verne’s classic 20,000 Leagues Under the Sea, published back in 1870, a character proclaims that “in the depths of the ocean, there are mines of zinc, iron, silver and gold that would be quite easy to exploit”. The Frenchman may have been right about the bounty beneath the waves – but the practicalities of securing them have proved trickier. From air compressors to hydraulic pumps, the years after 1975 saw several theoretical successes, yet the quantities of harvested ore remained too low to be economically viable. Bolstered by improvements in dredging technology, however, the situation has been transformed. In November 2022, to give one example, a Canadian operator called The Metals Company successfully extracted 3,000t of ‘nodules’ – essentially, sea rocks that contain precious minerals – from the ocean floor between Hawaii and Mexico, an area known as the Clarion- Clipperton Zone.

But, if the business case for deep-sea mining is improving all the time, even industry enthusiasts are worried about what it means for the health of the planet. “I discovered the polymetallic nodules that live on the seabed – and got a little bit horrified with the dredging technology that others were pursuing,” recalls Oliver Gunasekara, CEO of the US-based mining company Impossible Metals. Other experts make a similar point, with Dr Kirsten Thompson at the University of Exeter describing the potential of “irreversible damage” to marine environments if deep-sea mining increases. To a large extent, these concerns seem reasonable. According to work by the Deep Sea Mining Coalition group, for instance, stripping seabeds of their metallic crusts could destroy coral ecosystems that formed over thousands of years. Sucking up nodules risks upsetting the undersea environment too, while the sediment and noise whipped up by all this activity could cause distress to nearby whales and dolphins.

Whatever his personal worries over dredging, however, Gunasekara is convinced that deep-sea mining has to happen somehow – if nothing else, because of the immense importance of the minerals to the green revolution. “The biggest driver is the fact that we need massive quantities of these metals to move away from fossil fuels,” he stresses, adding that the World Bank has estimated that 500 times more metals are needed if humanity is to achieve net zero by 2050. Certainly, the ocean floor could be a boon in this respect: vital for electric vehicle batteries and wind turbines, Gunasekara notes that the Clarion-Clipperton Zone alone may contain six times the world’s known nickel reserves.

Can there be balance?

Is there a way, in short, of balancing the environmental impact of deep-sea mining with the rising demand for new minerals? Gunasekara believes there is. Fundamentally, his solution involves a shift in extraction technique. Rather than the traditional dredging strategy – sucking up nodules indiscriminately, ravaging ecosystems along the way – Impossible Metals is using undersea robots for a more subtle approach. First, autonomous robots are dispatched to the ocean floor. They then gather up nodules, before returning to the surface with their loot. Crucially, the process should theoretically keep environmental disruption to a minimum.

Trained to avoid nodules that have coral or other lifeforms attached, Gunasekara says Impossible Metals is working with marine scientists to perfect the relevant code. Just as importantly, Gunasekara’s robots don’t dredge. Rather, they use independent motors to hover above the seabed, avoiding the sediment storms other operations can bring.

Lacking other accoutrements of traditional deepsea mining, notably the pipes and surface vessels that can cause so much disruption, it’s clear that Gunasekara is excited by the project. “We’re not claiming zero impact – all extraction has an impact,” he says. “But our design goal was to absolutely minimise that.” Not that industry insiders should expect to see full-scale Impossible Metals robots scouring the ocean immediately: so far Gunasekara and his team have only developed prototypes suitable for depths of up to 25m. Even so, the aim is to have a full fleet ready by 2026, a plausible aspiration given what else is happening across the industry. Pliant Energy, for instance, is a New York company that’s developed stingray-shaped nodule extractors to suck up minerals. Firms from the UK to China, for their part, are making similar moves.

All the same, it’d be wrong to suggest everyone is enthusiastic about this robot-inflected future. For one thing, Thompson points out that even if machines are discerning enough to only harvest certain nodules, that’ll still disrupt an underwater environment shaped over literally millions of years. “Those areas,” she argues, “will never recover.” Like other environmentalists, Thompson has broader problems with deep-sea mining too. Rather than starting a new industrial revolution – albeit one with stronger green credentials – she suggests that humanity should instead address “fundamental issues” around resource use and management. Thompson is similarly sceptical of the argument made by many mining advocates, Gunasekara among them, that undersea extraction is better than wrecking the dry-land habitats of animals like orangutans. “We ignore these deep-sea creatures at our peril,” she says, “because we don’t understand how important they are for ecosystem structures.”

Deal or nodule?

Perhaps unsurprisingly, Gunasekara gives these claims short shrift. “The rail line has to be built, the power plant needs to be built,” is how he puts it, adding that from a geopolitical perspective, an added advantage of deep-sea mining is that it helps drag Western countries away from Chinese dominance of rare earth and other minerals. And if these philosophical disputes seem set to continue, there’s a similar lack of agreement around practical next steps. Currently, the International Seabed Authority (ISA), the body tasked with organising rules around mining in international waters, has until July 2023 to come up with new guidelines. But in March, diplomats from a range of countries accused the organisation of rushing proposals through.

And while Gunasekara and Thompson agree that what the ISA ultimately decides is important – especially as, in Thompson’s telling, what companies can and can’t do isn’t “rigorously formulated yet” – there’s a familiar sense of disagreement around what nation-states are doing domestically. On the one hand, countries like France are electing to ban deep-sea mining off their coastlines. On the other, the Cook Islands, a self-governing Pacific archipelago linked to New Zealand, recently approved mineral exploration licences in its territorial waters. To put it differently, it seems clear that the battle over deep-sea, both legally and rhetorically, is destined to rage on, even as firms like Impossible Metals get closer to their gold.

This article first appeared in World Mining Frontiers magazine.