Trillions of metallic nodules on the sea floor could help stop global heating, but mining them may damage ocean ecology
Last modified on Sun 29 Aug 2021 09.27 EDT
In a display cabinet in the recently opened Our Broken Planet exhibition in London’s Natural History Museum, curators have placed a small nugget of dark material covered with faint indentations. The blackened lump could easily be mistaken for coal. Its true nature is much more intriguing, however.
The nugget is a polymetallic nodule and oceanographers have discovered trillions of them litter Earth’s ocean floors. Each is rich in manganese, nickel, cobalt and copper, some of the most important ingredients for making the electric cars, wind turbines and solar panels that we need to replace the carbon-emitting lorries, power plants and factories now wrecking our climate.
These metallic morsels could therefore help humanity save itself from the ravages of global warming, argue mining companies who say their extraction should be rated an international priority. By dredging up nodules from the deep we can slow the scorching of our planet’s ravaged surface.
“We desperately need substantial amounts of manganese, nickel, cobalt and copper to build electric cars and power plants,” says Hans Smit, chief executive of Florida’s Oceans Minerals, which has announced plans to mine for nodules. “We cannot increase land supplies of these metals without having a significant environmental impact. The only alternative lies in the ocean.”
Other researchers disagree – vehemently. They say mining deep-sea nodules would be catastrophic for our already stressed, plastic-ridden, overheated oceans. Delicate, long-living denizens of the deep – polychaete worms, sea cucumbers, corals and squid – would be obliterated by dredging. At the same time, plumes of sediments, laced with toxic metals, would be sent spiralling upwards to poison marine food-chains.
“It is hard to imagine how seabed mines could feasibly operate without devastating species and ecosystems,” says UK marine biologist Helen Scales – a view shared by David Attenborough, who has called for a moratorium on all deep-sea mining plans. “Mining means destruction and in this case it means the destruction of an ecosystem about which we know pathetically little,” he says.
It is a highly polarised dispute. On one side, proponents of nodule extraction claim it could save the world, while opponents warn it could unleash fresh ecological mayhem. For better or worse, these mineral spheres are going to play a critical role in determining our future – either by extricating us from our current ecological woes or by triggering even more calamitous outcomes.
Polymetallic nodules were first discovered during the 1872-6 expedition of HMS Challenger, whose round-the-world voyage laid the foundations of modern oceanography. Hauled from seabeds more than 4,000 metres deep, they were initially thought to be formed from volcanic rocks and salts. Later it was shown they grow by absorbing metal compounds in seawater.
“Typically, a nodule takes shape around an object – like a clam shell – that has fallen onto the seabed,” says marine biologist Adrian Glover of the Natural History Museum, London. “The one we have just put on display formed around the tooth of a megalodon, a species of giant shark that became extinct more than 3m years ago. That shows how long a nodule takes to grow on the seabed – about a centimetre every million years.”
Despite this aeons-long accretion rate, trillions of nodules now cover the ocean bed. Some regions are so densely packed with them they look like cobbled streets. The Clarion-Clipperton Zone (CCZ) – which stretches from Mexico to Hawaii and covers more than 4 million square kilometres of seabed – is particularly rich in nodules, with estimates suggesting there is six times more cobalt and three times more nickel there than in the world’s entire land-based reserves.
These riches have sparked the interest of mining and dredging companies, which are now lining up to get approval to explore the Clarion-Clipperton. To date, more than 20 exploration contracts have been awarded by the International Seabed Authority (ISA), the UN body responsible for controlling mining on international waters.
Ultimately these companies hope to transform their exploration contracts into permits to extract the abyss’s mineral treasures and bring them to the surface. It will not be an easy task. On the dark ocean floor, pressure is 500 times greater than at the surface – the equivalent of lying underneath a stack of several dozen jumbo jets.
To get around these hurdles, huge surface ships will be needed – to lower pipelines attached to robot bulldozers, which would then trundle over the deep sea floor sucking up nodules, before pumping them back to the surface five kilometres overhead.
It sounds ambitious. Yet mining companies are upbeat. “We have built robot craft that run over the seabed to search for diamonds off the coast of Namibia and to build deep-sea pipeline trenches,” said Laurens de Jonge, manager of marine mining at Royal IHC, the Dutch supplier of maritime technology for dredging, offshore energy and mining.
“The abyss means working at greater depths and pressures which will certainly involve new challenges, including our main focus: to limit the environmental impact as much as possible. However, we do not expect major differences occurring between past operations and future nodule mining. I would anticipate that once a company has decided to commit to a seabed mining operation and has been given an extraction licence, it could probably get under way in around three years.”
As part of its plans, Royal IHC has designed a 16-metre-wide robot and built a three-metre test vehicle – called Apollo II – which would be able to gather about 400 tonnes of nodules in an hour and pump them aloft. Over two weeks’ operation, more than 100,000 tonnes could be removed this way. And after operating for 25 to 30 years – the anticipated limit for an ISA extraction licence – about 10,000 square kilometres of the seabed could be strip-mined.
Extraction on this scale makes many marine biologists blanch – for its likely effect on deep-sea life could be profound and widespread, a point stressed by marine biologist Callum Roberts, of York University. “Nodules provide the only hard substrates in the thousands of square kilometres of the fine sedimentary ooze that covers the abyssal plain,” he says. “They are critical attachment points for a variety of creatures that cannot live directly in mud.”
These residents include anemones, sponges, corals, nematode worms, and microscopic creatures called tardigrades – as well as octopuses, which have recently been found to lay eggs in sponges attached to nodules. “The biomass of the animals in the sediment is very low,” says ocean biologist Cindy van Dover, of Duke University. “However, the diversity is very high.”
In fact, vast numbers of species still remain to be discovered in the abyss, say scientists, and many would be obliterated by deep-sea mining before they have been identified. “As the mining machines thunder across the seabed, they would kick up fine, muddy clouds that would hang in the water, because no strong currents are there to disperse them,” says Scales in her recent book, The Brilliant Abyss. “Delicate animals caught in these clouds and unable to swim away, like corals and sponges, would be smothered and choked.”
Nor would there be any chance of a quick recovery from the onslaught. At these depths, where food and energy are limited, life proceeds at an extraordinarily slow rate. Populations could take centuries to recover.
These dangers were summed up in a recent report by the international conservation charity Fauna and Flora International. “Deep seabed mining will result in large-scale habitat removal,” it states. “It will also produce sediment plumes which will disrupt ecological function and behavioural ecology of deep-ocean species, smothering fundamental ecological processes over vast areas.”
For their part, mining companies stress they do not plan to start nodule dredging until full environmental assessments of their proposals are completed. These are now being worked on by ecologists, marine biologists and oceanographers.
In addition, companies such as Ocean Minerals point to the damage done by mines on land, which create sinkholes, trigger biodiversity loss, and cause widespread contamination of soil and surface water. “In our considered opinion, the impact of nodule mining will be magnitudes less than the equivalent impact of the mining on land for the volumes of metals we will need in future,” says Smit.
Pressure to obtain these metals in sufficient volumes is certainly going to become intense, analysts agree. One estimate, by the World Bank, suggests there will have to be a 500% growth in cobalt production by 2050 if demands for electric vehicle batteries and turbine manufacture are to be met. Nevertheless, deep-mining opponents say such forecasts still do not justify ploughing up the abyssal plain and point to two other approaches – metal recycling and alternative green technologies – that could reduce the need to mine for cobalt, manganese, nickel and copper.
In the first case, these elements could be extracted from old electric-car batteries and used to make new ones. This recycling would limit the need to mine for fresh supplies of metal ores. And the concept is a useful one, acknowledges Professor Richard Herrington, head of earth sciences at the Natural History Museum, London. “Recycling is going to be important but it will not be enough on its own. By 2035, we might have about 35 to 40% of these metals from recycling – if we can get our act together now.
“Where we get the other 60 to 65% is a different issue and a museum like ours has a real role to pay here – to get people to think about where we should extract the metals we need to save the world. These issues are going to shape our lives in the next few decades, after all.”
Not everyone agrees with the claim that cobalt, manganese, nickel and copper are necessarily vitally important, however. “There are a whole range of viable alternative battery technologies that could avoid using these metals,” says Matthew Gianni, of the Deep Sea Conservation Coalition, a Dutch-based alliance of international green groups. For example, lithium iron phosphate batteries are now looking very promising.”
The current rush to extract nodules is therefore misplaced, say green groups who argue that engineers and entrepreneurs should be given a time to develop new battery and power plant technologies – like lithium iron phosphate batteries. Hence their calls for a deep-sea mining moratorium.
The problem is that the timetable for reaching net zero emissions of greenhouse gases is now so tight. The world cannot wait for much longer for new battery technologies to emerge. It needs to eliminate fossil-fuel burning urgently.
Mining companies also deny they are rushing ahead with their plans. “We are still gathering in the science and I would say commercial operations are unlikely to start until the end of the decade,” says Chris Williams, managing director of UK Seabed Resources, which has its own plans to extract nodules from the Clipperton-Clarion Zone.
“I am confident we will be able to show that extracting polymetallic nodules will have a lower impact on the environment than will be the case with the opening of new mines on land or the expansion of existing ones.”
However, the notion that nodule-mining negotiations are going to proceed smoothly with agreement about strict extraction rules eventually being reached by the International Seabed Authority was thrown into disarray several weeks ago.
The Pacific Island state of Nauru – one of ISA’s 167 member states – activated an obscure sub-clause in the UN Convention on the Law of the Sea that allows countries to pull a two-year trigger if they feel negotiations are going too slow. The ISA now has two years to agree regulations governing deep-sea mining – if they don’t, mining contractors will be allowed to begin work regardless.
Nauru is partnered with a mining company called DeepGreen and says it fears being overwhelmed by rising ocean levels and wants to speed up the exploitation of abyssal nodules as a way of promoting green technologies that might save it from inundation. Its activation of the ISA’s two-year clause has caused some consternation in the industry – and among deep-sea mining opponents who fear attempts are being made to stampede the world into deep-sea mining before its consequences can be properly assessed.
For its part, ISA has played down the implications of Nauru’s move. Others are less sanguine. “This could really open the floodgates,” says Gianni.
Such prospects only strengthen the urgency of assessing the likely effects of deep-sea mining, say scientists. It is a point stressed by Andrew Sweetman, professor of deep-sea ecology at Heriot-Watt University, Edinburgh, who has been involved in carrying out deep-sea mining impact assessments for governments and mining companies.
“We are living in a world where more and more people want to have the latest cellphones as well as electric vehicles and wind and solar power plants that will help in achieving net zero emissions. And these require metals like cobalt and manganese.
“On its own, recycling these metals is unlikely to provide the ingredients we need for these devices, so mining is going to be important. On land it is associated with all sorts of problems and eventually there will be a push for deep-sea mining – and in the end it will happen. That means we need to get as much information about its impact so we are best placed to limit the damage.”
The world’s appetite for copper, manganese, cobalt, nickel and other elements needed for green technology is rocketing.
Global use jumped from 17.8m tonnes in 2009 to 24.5 million in 2019, driven by demands from manufacturers of renewable energy plants and electric vehicles. Copper’s high electrical conductivity, durability and malleability make it invaluable.
Manganese compounds have been used by humans for millennia, with traces found in pigments used in cave paintings and Roman glassmaking. Today it is used in the form of electrolytic manganese dioxide, a key ingredient of lithium-ion and alkaline batteries.
This vital ingredient of guitar strings is resistant to corrosion and oxidation, and easily forms alloys with other metals. More recently, it has become a main component for electric vehicle batteries.
This is the most controversial metal that is powering green technology. Used to make batteries, and solar and wind power plants, more than half the world’s supply is found in the Democratic Republic of Congo, where small independent mines have used children as young as seven to dig cobalt ores.
Three key sources are being explored in the deepest parts of Earth’s oceans.
These are underwater volcanoes that spew sulphur compounds that include sulphides of silver, gold, manganese, cobalt, and zinc.
Many of these underwater peaks are known to be rich in cobalt chemicals and have sparked the interest of mining companies.
These litter the bottom of the deep ocean. Mining companies have shown most interest in this source because of the relative ease of extraction. Most plans have earmarked the Clarion-Clipperton Zone as the target for mining, although some have pinpointed other areas. Florida’s Ocean Minerals wants to mine off the Cook Islands in the Pacific, for example.