Nautilus undersea mining collecting machine and bulk cutter

Deep-sea mining: plundering the seafloor’s minerals

Image credit: Mike Smith

Decades after the discovery of vast deep-sea mineral deposits, has the lure of metal-rich ore finally tempted the mining industry to pillage the deepest frontier?

The technological developments required to exploit the resources known to exist in the harsh deep-sea environment are, although considerable, perhaps the least of the industry’s worries. After all, it can draw on the experiences of the offshore energy industry, where operations at depths of 3-4km are now almost routine.

The real difficulties begin when one tries to align that with the firm commodity prices, structured regulatory framework and environmental understanding of each area to be mined that are required to take the plunge. And then there is the small matter of the social contract: sufficient agreement that the deep ocean should be exploited at all.

The Canadian-registered, Omani and Russian majority-owned Nautilus Minerals may in late 2019 be the first company to commercially exploit a deposit of ‘seafloor massive sulfides’ (SMS). These are a metal-rich crust containing copper, zinc, gold and silver that lie 1,700m below the surface of the Bismarck Sea, the territorial waters of Papua New Guinea.

The world’s first giant deep-sea mining machines were delivered by UK-based Soil Machine Dynamics (SMD) to Nautilus Minerals in Papua New Guinea in 2017. However, none have yet been tested at depth due to contractual problems with completion of the production support vessel being built in China.

SMD’s Solwara 1 project, which aims to extract SMS deposits from the location, uses three machines that are needed to work the metal-rich SMS crusts in the Solwara 1 field. At these depths, copper is found at concentrations of seven times that of the average land-based mine. The first machine used as part of the extraction is the auxiliary cutter, which creates a level working surface for the subsequent bulk cutter and collector machines.

Nautilus auxiliary cutter diagram

Image credit: Nautilus/E&T

The bulk cutter is the main production machine and the heaviest deep-sea mining unit ever built, weighing in at over 300 tonnes. “Designing a ship-based launch and recovery system was challenging for something of that size,” says Stef Kapusniak, mining business development manager at SMD. “We settled on a cantilever system. The installed power of the cutter head is also bigger than any other rock cutter at 1.2MW. The power is supplied via an umbilical from the vessel.”

In the planned mining technique, the giant bulk cutter grinds up the seafloor with each pass, before the collector sucks up material from the piles made by the bulk cutter, which is then transferred via a riser pipe to the production support vessel on the surface, where it is dewatered. The dewatered ore slurry is transferred to another vessel, which transports it to China for processing.

Each of the mining vehicles is controlled remotely from the ship’s control room via an umbilical. This supplies power to multiple copper cores, as well as communications, data and control commands via fibre-optic cables, which are all wrapped in an armoured casing. The umbilical has a bend restrictor to prevent it from contacting the seabed. Each machine also has an intervention panel that can be accessed by a remotely operated vehicle (ROV), which can help couple and uncouple hoses and tools without the need to return the big machines to the surface and can also help in emergency situations.

An environmental impact statement from the company claims that operations at the mine site will produce minimal particulate plumes – which could potentially smother sea life – on a similar scale to those produced naturally by nearby hydrothermal vents, or ‘hot smokers’.

An additional environmental concern is that once the seawater has been removed from the ore-bearing substrate it must be returned to the ocean, and it too will carry small particles that could form a plume where it is expelled. The concentration of these particles is controlled in the operating licence.

Kapusniak views these concerns with a wry logic: “No one wants their gold dust to float away. We have made and tested key sub-assemblies of the machines and used computational fluid dynamic assessments to optimise the cutter heads so that escape of material is minimised on each machine.”


What lies beneath?

Most mineral resources that are attracting the attention of would-be subsea miners fall into three categories:

Polymetallic nodules

Scattered on the seabed at depths of 3.5 to 6km, these golf ball- to potato-sized nodules can form around a nucleus of fish bones or shark teeth on which minerals have accumulated over millions of years.

Consisting of mostly manganese oxides, they also contain metals such as nickel, cobalt and copper, and were first identified as potentially economically attractive back in the 1960s. They also have a high local impact on seabed life forms, for example, trawling for shellfish. But at much greater depths, in colder waters, biodiversity would be slow to recover.

Seafloor Massive Sulfides (SMS)

These metal-containing deposits are located around mid-ocean ridges where the sea floor is, or was, volcanically active. Mineral-rich superhot water from underlying magma meets cold deep seawater and forms a crust on the seafloor at a depth that is often richer in minerals, particularly copper, than can be found in land deposits. Active ‘hot smoker’ vents with their rich biological diversity, often compared to coral reefs or rainforests, are likely to remain off-limits. However, the seabed contains much larger areas of extinct or inactive zones of SMS, though these are harder to find. Most of the rights to the exploitation of SMS at the mid-Atlantic ridge have already been granted by the International Seabed Authority.

Cobalt-rich ferromanganese crusts

These form by precipitation from seawater on to hard rock surfaces over millions of years, mostly on the flanks of underwater seamounts and extinct volcanoes, often because of subsea volcanic activity in the waters of island states like the Cook Islands. They contain iron, manganese, cobalt, nickel and other minor metals. Rugged terrain may make mining challenging but may result in the least environmental impact.

Japan’s Oil, Gas and Metals National Corporation, JOGMEC, has also been testing deep-sea mining equipment within its exclusive economic zone (EEZ) at the Okinawa trough of the East China Sea. Working at 1,500m, in 2017 the company demonstrated a successful ore-lifting to a surface vessel from a sulfide mound, proving the deep-sea mining concept at depth for the first time.

The economic case for extraction is highly dependent on cyclical commodity prices. Metallic ores such as copper, cobalt, manganese, nickel, tellurium and lithium are vital to produce electric-vehicle batteries, solar panels and wind turbines, and are currently sourced from depleting surface mines. Increasing demand on the supply side is set to drive commodity prices upwards, justifying the exploitation of the ocean and the emergence of a new multi-billion-dollar industry.

Many countries view the development of the deep sea and secure access to its mineral resources as strategically vital. World production of key metals is geographically concentrated; some 97 per cent of global demand for rare earth metals is owing to the manufacture of electronic products, and this currently depends on Chinese land-based supplies. There are other sources that are not currently exploited, notably in Australia. In 2017, the Democratic Republic of Congo was responsible for 58 per cent of global cobalt production, while Chile and Peru were producing 40 per cent of the world’s copper.

The race is on for countries to define the boundaries of their Exclusive Economic Zones (EEZs) – an agreed band of jurisdiction extending 200 nautical miles from a coastal state’s boundaries, and within which the state has special rights of exploration and use of marine resources including mineral resources. Importantly, within these EEZs the state makes the rules.

Small Pacific island nations such as Fiji, Papua New Guinea and Tonga have vast EEZs relative to their populations. These nations see deep-sea mining as a way to boost faltering economies and to offer opportunities for their citizens. The island groups all lie near known subsea deposits. For example, the Cook Islands’ EEZ is estimated to hold 15-20 per cent of the world’s known reserves of cobalt. Such possession is likely to increase in value as cobalt’s role in the post-carbon economy expands its use.

Paul Lynch, of the Cook Islands’ Seabed Minerals Authority, says: “We have passed legislation aimed at a positive conservation and environmental outcome where we will permit zoned areas of resource utilisation across our whole EEZ (almost two million square kilometres). Partnership with the right corporate entities, and training for young Cook Islanders, is essential.”

Nautilus Minerals

Papua New Guinea

The imminent commencement of mining activities by Nautilus Minerals in Papua New Guinea’s exclusive economic zone has been predicted since 2013.

The site, Solwara 1, is a small, mineral-rich inactive hydrothermal vent site where seafloor massive sulfides (SMS) will be exploited. 2019 is cited by the company as a possible start date.

Nautilus Minerals has also explored the seabed in nearby Pacific countries, although it is currently struggling financially and the contract for the specialist ship that seafloor robots built by Soil Machine Dynamics (SMD) would tether to has been rescinded by the Chinese shipbuilder. The company is currently working to resolve the issue by finding another owner who could complete the shipbuilding contract and lease the ship to Nautilus.

The players range from small, often precariously funded, entities dependent on repeated rounds of financing, to the state-sponsored efforts of Korea, China, Japan and India. Both the UK and Norway view deep-sea mining as a potentially huge emerging industry where the countries can build on their worldwide expertise in oil and gas technology and, like other state entities, secure access to strategic minerals.

Torgeir Stordal, director of exploration at Norway’s Petroleum Directorate, says: “Right now, the stage of development of this nascent business is like North Sea oil in the 1960s. We are making coarse level mapping of the seabed resources prior to licensing, and companies will make the detailed mapping as part of their exploration effort.” Norway is also assisting developing countries from Madagascar to Nigeria to demarcate their own EEZs, by establishing the outer limits of their continental shelves.

What is unusual about this new industry is that, unlike oil and gas, terrestrial mining or deep sea fisheries, the environmental and regulatory regime will pre-date the development of the industry, and that is important. The mining industry has not exactly covered itself in glory when it comes to environmentally sensitive processes, particularly in the developing world where regulatory regimes are weakly enforced.

Christopher Williams of UK Seabed Resources (wholly owned by Lockheed Martin UK) says: “It is right that this new industry be held to different and higher environmental standards. We will need a social licence from the rest of humanity to exploit the deep sea, as well as an economic, regulatory and contractual licence to do so.” Williams points out that the UN Convention on the Law of the Sea (UNCLOS) requires that the International Seabed Authority (ISA) is bound to make the regulations equitable with land-based mining.

If there has not yet been a subsea ‘El Dorado’ for mining companies, the pre-exploration mapping phase has heralded a golden age for deep-sea biology. This is because the economic mapping of mineral deposits goes hand-in-hand with the requirement for the assessment of marine biodiversity in depths that are rarely accessed by national scientific cruises.

Some 26 exploration contracts of 15 years each had been approved by the ISA as of May 2017, covering an area of seabed of 1.2 million square kilometres. During only two UK Ship Register (UKSR)-funded research and mapping cruises in the Pacific Ocean Clarion-Clipperton Zone, marine scientists spent a combined 50 days on station and covered over 700km of seabed. These scientists were also generating over 57,000 images of the seafloor, collecting more than 23,000 samples and, as of 2017, producing 50 peer-reviewed academic papers and conference presentations.

Slowly but surely, all of the elements required to propel this nascent area into a fully fledged industry – even outside those EEZs – are floating into place.

Exploration project

Atlantis II Deep

Manafai International was awarded a 30-year mining licence by the Saudi and Sudanese governments in 2010 to extract zinc, copper, silver and gold from the Atlantis II Deep in the Red Sea, which holds the world’s largest known massive sulfide deposit. An advanced exploration project within the two countries’ common Exclusive Economic Zone, it builds on work funded by the Saudis that was carried out by German company Preussag AG in the 1970s to a pre-pilot mining phase.

Situated 100km offshore, mid-way between Jeddah and Port Sudan, and approximately 2km deep, metal-rich muds are accumulating in one of several basins filled with hot, highly saline brines.

“We know there are a variety of other metals present, including lithium, but we have yet to quantify the precise amounts,” says project manager Dan Hamer. “Previous coring penetrated on average only 8.5m, although the muds are less than 25m deep in places. There’s plenty of scope for upside potential.”

The Atlantis Deep is a depression in the Red Sea floor, forming as the African and Arabian tectonic plates diverge. Hydrothermal circulation releases metal-rich geothermal brines along the plate borders. The proposed mining system will suck up a mud-brine slurry, which could be transported either vertically to a production support vessel for processing or by submarine pipeline direct to a shore-based facility. Filtered seawater could be returned to the deep to minimise sediment plume formation.

Hamer and his team expect to be drilling in the area to better quantify the resource in early 2019. Hamer says: “After that there will be a feasibility study phase, perhaps for two years, with a great deal of environmental work, and only when everyone is happy would we consider a trial mining phase.”

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