Deep-sea mining – plans are taking shape
Fundamental to technological progressMobile phones, internet and streaming TV have become as firmly embedded in our daily lives as electric vehicles, wind turbines and storage systems for the photovoltaic electricity generated in our homes. The increasing digitalization and electrification of our lives, however, has its price. To produce the necessary technology and expand the networks, large quantities of metals will be required, especially those of the rare earth group. Tungsten makes telephones vibrate, gallium and indium are necessary for light-emitting diode technology in lamps, semiconductors depend on silicon metal and hydrogen fuel cells require platinum-group metals.
Beside these, other mineral raw materials such as copper, nickel, cobalt, lithium and tellurium also have to be extracted from the earth using costly mining processes. As a rule, these activities are highly destructive to the environment, and in some countries the mining of raw materials also leads to corruption, war and the displacement of local inhabitants, and can have severe consequences for indigenous populations, especially when the mining is carried out in an unregulated or illegal manner.
- 5.1 > The European Union has to import many of the critical raw materials needed in Europe and relies on delivery of these from a few specific countries. There is an especially great dependency, for example, on China (99 per cent of all light rare-earth metals) and Turkey (98 per cent of the required borates).
- 5.2 > The global energy transition can only succeed if sufficient mineral raw materials are available. As many as eleven different metals are needed in the construction of wind turbines, photovoltaic systems and energy storage units.
- These consequences loom even larger when we consider the fact that the demand for these metals and minerals can only increase with the various transformations in energy and transportation systems that result from our responses to climate change. Just two examples: It is now estimated that the European Union will require up to 18 times more lithium and five times more cobalt for the production of electric vehicles and energy storage in 2030 than was needed in 2020. According to the European Commission, the demand for rare-earth metals contained in the permanent magnets used for electric cars, digital technology and wind generators could increase tenfold by 2050. How to meet this mounting demand?
To date, there are only two areas on Earth where people have not yet engaged in commercial mining. One of these encompasses the entire Antarctic region, including all waters and land masses south of 60 degrees south latitude.
The Protocol on Environmental Protection to the Antarctic Treaty prohibits both the mining of mineral resources and the extraction of energy resources in this region. The latter include fossil materials such as coal, oil and natural gas. The second area as yet untouched by commercial mining is the bed of the deep sea. This can be defined as the bottom of the world’s oceans at water depths greater than 200 metres. But the rising global demand for mineral resources is increasingly drawing the attention of the mining industry towards the oceans. There are a number of metals present in commercially promising quantities in the deep sea, including those of the rare earth group. Geologists distinguish three different kinds of potentially minable deep-sea ore deposits, each of which, unlike the deposits on land, contains a large variety of different metals. These three groups are manganese nodules, cobalt-rich ferromanganese crusts, and massive sulphides.
- 5.3 > If mankind wants to limit global warming to two degrees Celsius by the year 2100, it will have to completely restructure its energy sector. According to the World Bank, the demand for products in the field of energy technology will increase significantly by 2050, especially for graphite, lithium, cobalt and indium.
Manganese nodulesManganese nodules are mineral bodies that are black-to-brown in colour, generally round with a diameter of one to 15 centimetres, and usually structured like an onion peel. They form primarily on the deep ocean floors covered by sediments (particle deposits) at water depths of 3500 to 6500 metres. Oxygen-rich deep water is necessary for their formation as well as a grain or nucleus, around which multiple layers of iron and manganese oxides are deposited over millions of years, along with minor and trace metals such as nickel, cobalt, copper, titanium, molybdenum and lithium.
The nucleus is usually a piece of hard sediment or a nodule fragment, but may occasionally also be a fragment of basalt or other rock, or a piece of broken clam shell. Scientists have also found nodules that formed around a shark’s tooth or the tiny inner-ear bones of a whale. The metals, on the other hand, are natural components dissolved in the seawater and the pore waters within the sediments, and are deposited onto the manganese nodules through diagenetic and hydrogenetic processes.
Diagenetic accretion occurs when metal oxides precipitate from the pore waters that circulate through the upper sediment layers of the seabed. Among other elements, these pore waters contain dissolved manganese, which diffuses upwards and trickles out of the sea floor due to differences in concentration. On contact with the oxygen-rich ocean water it is oxidized and manganese oxides precipitate. These accumulate in concentric spheres around the nucleus. Other metals dissolved in the pore waters, including copper and nickel, are also captured with the manganese oxide. These originate primarily from the microbial breakdown of organic material in the sea floor. They may also be released, however, through the dissolution of calcareous or silicate shells of dead plankton in the sediments. As a rule, manganese nodules extract more than 80 per cent of their metals from the pore waters. This constant supply of material allows them to grow, albeit no more than a few centimetres over a time period of a million years.
- 5.5 > Manganese nodules grow in one way through the precipitation of metal oxides from the pore waters in marine sediments (diagenetic accumulation), and in another by the precipitation of manganese and iron oxides directly from the seawater (hydrogenetic accumulation). These two processes can occur simultaneously.
- Hydrogenetic processes also contribute to the growth of most manganese nodules. These involve the precipitation of colloids (minute particles from one nanometre to one micrometre in size) of hydrated manganese and iron oxides directly from the seawater. Manganese nodules that are formed exclusively, or mostly, through hydrogenetic processes are found on the slopes or peaks of seamounts. Their composition is determined by the water chemistry and by biogeochemical processes between the seawater and the particles it contains. Nodules formed by hydrogenetic processes grow extremely slowly. Their diameter increases by only a few millimetres per million years. However, they accrete more cobalt and rare earth metals than the nodules of predominately diagenetic origin.
Manganese nodules are typically found lying detached on the sea floor, with usually between one-third and two-thirds of the nodule embedded in the sediment. In some areas there are only a few nodules per square metre of seabed, while other areas can have as many as 1000. The largest and economically most attractive occurrences are found in the manganese nodule belt of the Clarion-Clipperton Zone (CCZ). This is situated in the near-equatorial region of the North Pacific between Hawaii and Mexico. Other significant manganese nodule deposits are found in the Peru Basin (southeast Pacific), the Penrhyn Basin (western Pacific) and in the central Indian Ocean.
- 5.6 > The commercially most interesting occurrences of manganese nodules are found in the Clarion-Clipperton Zone of the North Pacific, the Peru Basin, the western Pacific Penrhyn Basin and the central Indian Ocean.
- The manganese nodule belt of the Clarion-Clipperton Zone in the Pacific, with an area of around five million square kilometres (circa 5000 kilometres long and 1000 kilometres wide), is larger than the European Union. About three-fourths of this deep-sea area is characterized by a flat sea floor. Seamounts rise up throughout the remaining areas, some with heights of up to 1000 metres. On the deep-sea plains there are some areas where almost all of the nodules are large, ranging from four to 15 centimetres in diameter, and others where almost all the nodules are smaller than four centimetres. Smaller nodules cover around 85 per cent of the deepsea plains in the Clarion-Clipperton Zone. Areas with larger nodules comprise about twelve per cent, and nodules are absent in the remaining three per cent of the areas. In areas especially rich in nodules, the clumps of ore are so dense that they commonly have a wet weight between 15 and 30 kilograms per square metre of seabed area. It is estimated that the Clarion-Clipperton Zone contains nodule deposits with a total wet weight of 25 to 40 billion tonnes.
These have attracted particular commercial interest because of their high contents of manganese (30 weight per cent), nickel (1.4 weight per cent), copper (1.1 weight per cent) and cobalt (0.2 weight per cent). These four metals are necessary, among other things, in the production of communication technology and electric cars and for steel refinement. Along with nickel and manganese, cobalt, which until now has primarily been mined in the Democratic Republic of the Congo, is also a particularly indispensable component of modern lithium batteries. Compared to all of the known deposits on land, the manganese nodules in the Clarion-Clipperton Zone alone contain around 3.4 to five times more cobalt, 1.8 to three times more nickel and 1.2 times more manganese. Moreover, the nodules also contain comparatively high proportions of titanium, molybdenum and lithium.
Cobalt-rich ferromanganese crustsCobalt-rich ferromanganese crusts are hard coatings of iron and manganese oxides that form on the slopes of seamounts and, like hydrogenetic manganese nodules, obtain most of their metals from the surrounding seawater. Unlike in the flat deep-sea plains, no sediments are deposited on the slopes of the seamounts. Ocean currents wash away sinking particles rather quickly, so the ferromanganese crusts are only able to grow extremely slowly – about one to five millimetres per million years.
Various metals that are crucial for the production of modern energy supply, computer and communication systems are concentrated in the crusts. These include cobalt, titanium, molybdenum, zirconium, tellurium, bismuth, niobium, tungsten, rare earths and platinum. The rare metalloid tellurium, for example, is used both for cadmium-telluride alloys in thin-film photovoltaics and for bismuth-telluride alloys in computer chips.
- 5.7 > Ferromanganese crusts are mainly found in marine regions with the oldest oceanic crust, where the ore deposits have had the most time to grow. This is the case in the western Pacific, for example.
- Around two-thirds of the occurrences of cobaltrich ferromanganese crusts that are considered significant for deep-sea mining are located in the Pacific Ocean, while 23 per cent are in the Atlantic and about eleven per cent in the Indian Ocean. Deposits in water depths from 800 to 2500 metres are considered to be commercially promising. The known crusts are generally three to six centimetres thick, in exceptional cases sometimes up to 26 centimetres, so experts calculate that they contain 60 to 120 kilograms of ore per square metre of slope surface. The total global quantity of cobalt-rich ferromanganese crusts is estimated at 40 billion tonnes, whereby only half of these could be profitably mined given the present state of knowledge. To date, however, much fewer than one-tenth of the known occurrences have been studied in detail.
Massive sulphidesSea-floor massive sulphides are metal-sulphur compounds (metal sulphides) that form at hydrothermal vents on the sea floor, in water depths of 1600 to 4000 metres. These hydrothermal deposits are associated with volcanic structures and therefore occur primarily at tectonically weak points in the Earth’s crust, for example, at mid-ocean ridges, at island arcs and in back-arc spreading zones. They form as a result of the circulation of seawater through the uppermost three kilometres of the oceanic crust. The seawater is heated by deep-lying heat sources (magma chambers) and transformed into a hot, acidic and highly concentrated solution that can dissolve metals from the volcanic rocks.
The hot hydrothermal solution eventually rises and seeps out of the sea floor at specific sites. When it comes into contact with the cold, oxygen-rich seawater, the dissolved metals are precipitated in the form of metal sulphides. These include, for example, pyrite, chalcopyrite and sphalerite.
As a result of the focused, upward flow of the hydrothermal solution at the hot seeps, spectacular chimney-like structures called “black smokers” are formed. These can reach heights of 20 or 30 metres, or even more. At some point, however, the chimneys become unstable and fall apart. Another chimney then begins to form and grows to a certain height until it also collapses. This continuous successive process results in the formation of metal sulphide mounds on the sea floor, which are subsequently further altered and consolidated by internal chemical reactions through the mixing of the hydrothermal solutions with penetrating seawater. These ore deposits can be several hundred metres in diameter and several tens of metres thick. In addition, the hydrothermal solutions can also precipitate their load of metals beneath the sea floor. This forms a zone of mineralization called a stockwork.
- 5.8 > Massive sulphides form at hydrothermal seeps, which only occur at tectonically weak points in the Earth’s crust, for example at mid-ocean ridges, in back-arc spreading zones and at island arcs. As yet, however, only the occurrences at hydrothermal seeps that have cooled down are considered to be minable.
- The sea-floor massive sulphides are the present-day counterparts to the fossil volcanic massive sulphide deposits on land. The latter are important sources of copper, zinc, lead, silver and gold. These same metals are found in the massive sulphide deposits on the sea floor. However, the current deposits in the sea contain additional minor and trace metals that are important for modern high-tech applications. These include cobalt, antimony, indium, selenium, tellurium, gallium, germanium, bismuth and molybdenum.
More than 630 active hydrothermal seeps with proven metal sulphide accumulation are now known to scientists. But hydrothermal fields always contain a combination of active and inactive areas. In this case, inactive means that no hydrothermal solutions are presently seeping out of the sea floor. For two reasons, only the inactive areas can be considered for possible mining of the massive sulphides. For one, it is assumed that there is less danger of the destruction of rare deep-sea ecosystems here than at active seeps. For another, in the active areas the high temperatures of several hundred degrees Celsius and strongly acidic solutions would probably damage the mining equipment in a very short time.
As yet, only a few completely inactive massive sulphide deposits are known. This is because inactive deposits are much more difficult to find than the active seeps. The latter can be located comparatively easily on the basis of their chemical signature and the particles that the escaping hydrothermal solutions produce in the surrounding seawater.
Guardian of the heritage of mankindAround 81 per cent of all known manganese nodule fields, 46 per cent of the ferromanganese crusts and 58 per cent of massive sulphides are located in international waters, and therefore do not fall under the jurisdiction of any individual nations. Rather they belong to the common heritage of mankind, as Article 136 of the United Nations Convention on the Law of the Sea defines the sea floor outside of the Exclusive Economic Zone.
This heritage, which encompasses about 42 per cent of the Earth’s surface, is managed by the International Seabed Authority (ISA), which has its headquarters in Kingston, Jamaica. It regulates and oversees all activities related to the commercial use of the international seabed and its subsurface. Furthermore, it is the obligation of the ISA to ensure the balance of interests between industrialized and developing countries as established in the Law of the Sea. Because no deep-sea mining is being carried out at an industrial scale as yet, its main tasks at present are to issue and oversee contracts for exploration of deep-sea deposits, to draft regulations for future mining, and constantly update the adopted statutory foundations. To date, 167 nations and the European Union have joined the ISA.
- 5.9 > Metal sulphides are precipitated where high-temperature hydrothermal solutions rise out of the sea floor and mix with cold, oxygen-rich seawater. They are deposited and, over time, form spectacular chimney-like structures called black smokers.
- Applications for an exploration contract can be submitted by either states or private companies. As a prerequisite, however, the applicant has to pay a fee of USD 500,000 and the home state of the company, known as the “Sponsoring State”, must support the application. In addition, the state must have adopted and implemented its own marine mining legislation, which it can use to verify compliance with the licensing obligations as well as the company’s financial and technical capabilities at any time. National regulations on marine mining may not be more permissive than the international regulations in this regard. The Sponsoring State is accountable for the activities of the contract partner it supports. In Germany, the State Authority for Mining, Energy and Geology (LBEG), headquartered in Hannover, is responsible for overseeing exploration activities.
Through its Federal Institute for Geosciences and Natural Resources (BGR), Germany itself holds exploration contracts for two areas in international waters. The first of these has been valid since 2006 for the exploration of manganese nodule deposits. The area involved consists of two tracts, both of which are located in the Clarion-Clipperton Zone in the Pacific Ocean. One tract lies in the central area of the manganese nodule belt, and the other is an area of about 60,000 square kilometres in the eastern part of the zone. Regarding the latter, around 20 per cent of the area may be considered minable for manganese nodules because only there is the seabed flat enough and the nodules present at a sufficient density to make mining worthwhile.
The second German exploration contract area encompasses a 10,000 square kilometre deep-sea region of the Central Indian Ridge and the Southeast Indian Ridge in the southwestern Indian Ocean, where abundant occurrences of sulphides are presumed to be present. Geologists of the BGR, together with deep-sea experts from other German research institutes, have been regularly carrying out expeditions to the contract area since 2015 in order to determine the extent of the deposits there as well as to study species diversity and evaluate the impacts of possible mining activity. In the German contract area they have now discovered twelve sulphide deposits with 30 active and 34 inactive sites (e.g., sulphide mounds with numerous chimneys). Based on chemical and physical investigations in the water column, evidence has been found for twelve additional deposits.
- 5.10 > Since 2002 the International Seabed Authority has issued 31 contracts for exploration of the sea floor for mineral resources. These comprise 19 contracts for the exploration of manganese nodules, five for ferromanganese crusts and seven for massive sulphides.
Plans are progressingSince the year 2002 the International Seabed Authority has issued 31 contracts for exploration rights for mineral resources on the sea floor. There are 19 contracts for the exploration of manganese nodules with areas of around 75,000 square kilometres each, an area larger than the German state of Bavaria, five contracts for the exploration of ferromanganese crusts with areas of 3000 square kilometres each, and seven contracts for the exploration of massive sulphides in areas of 10,000 square kilometres each. With all of the contracted areas together, the ISA has so far authorized a sea-floor area of around 1.5 million square kilometres for the exploration of resources, an area as large as France, Spain and Germany combined.
Each contract has a duration of 15 years and includes the option for multiple extensions of five years each time if the contracted party has been unable to complete the exploration work for reasons beyond its control (for example, due to a pandemic), or if the global economic situation precluded the mining of raw materials in the deep sea. Holders of an exploration licence also have preferential rights to subsequent mining and are allowed to test their technology for raw-material production in the deep sea. For this, however, they are required to have an environmental impact statement approved and recognized by the ISA Legal and Technical Commission.
Deep-sea mining technologyMANGANESE NODULES: To date there has been no mining of manganese nodules. But over the past ten years at least five different companies and government institutions have contributed to its technological advancement by testing initial prototypes for future mining tools, albeit at reduced size and weight scales. The Korean research institute KIOST, for example, has designed a collector for manganese nodules as well as a conveyor system for transporting the nodules to the sea surface, and has already tested both of these in water depths of 1200 and 1400 metres.
A water depth of 4400 metres was achieved in 2017 with the basic chassis assembly of the manganese nodule collector Patania I, which was developed and successfully tested by the Belgian company DEME-GSR. The company has an exploration contract for the Clarion-Clipperton Zone. In September 2018 it publicly presented for the first time the Patania II collector, which had been upgraded with a manganese nodule collection system. An early deep-sea deployment of this prototype in the contract area (also at a water depth of 4400 metres) in 2019 failed due to technical problems with the cable connecting it to the ship. A second test in the spring of 2021, however, was successful, and was closely monitored by European researchers in order to gain information about the impacts of nodule mining on the marine environment and to evaluate the observation systems.
- 5.11 > Patania II, a caterpillar-like collector of manganese nodules made by the Belgian company DEME-GSR, is twelve metres long, 4.5 metres high, four metres wide and weighs 25 tonnes. The prototype was tested successfully in the spring of 2021 in the Clarion-Clipperton Zone at a water depth of 4500 metres.
- Both the Belgian and South Korean manganese nodule collectors are caterpillar-like vehicles in design, and both employ a hydraulic collection system to pick up the loose nodules lying on the sea floor. The Indian contract holder MoES, on the other hand, is adopting a mechanical concept for collecting the nodules, and is developing a mobile system with barbed shapes to rake up the nodules. After they are picked up, the nodules are cleaned, crushed and transferred to a vertical conveyor system. Depending on the design used, the nodules are then transported to a delivery platform at the water surface via a pneumatic process or by the use of a slurry. There they are dewatered and loaded onto bulk carriers for transport to shore.
- COBALT-RICH FERROMANGANESE CRUSTS: For mining ferromanganese crusts, the China Merchants Industry Holdings (CMI) has developed a prototype that was successfully tested at a water depth of 1300 metres in the South China Sea. The machine not only proved its ability to move along the sea floor, but also to cut and crush ferromanganese crusts. Dislodging ferromanganese crusts from the subsurface of the sea floor is a technical challenge, because the crusts often replicate the form of the underlying bedrock surface. For example, if there are boulders, rounded blocks and slabs of rock, or the flow structures of ancient lava beneath the crusts, the crusts will precisely follow those structures. As a result, mining machines could easily become stuck on very uneven grounds. The Chinese vehicle, however, appears to move in steps that compensate for the unevenness. For cutting and crushing the crusts, engineers rely on designs that employ either a high-pressure water jet or rotating roller bits like those used in mining coal.
- 5.12 > The now bankrupt Canadian company Nautilus Minerals developed three remote-controlled underwater vehicles for mining a massive sulphide deposit in the Bismarck Sea off Papua New Guinea: a shaper (auxiliary cutter, right), a bulk cutter (centre) and a collector (left).
- MASSIVE SULPHIDES: The mining of massive sulphides will probably prove to be equally difficult, but initial progress is being made here as well. The now bankrupt Canadian company Nautilus Minerals, for example, developed a process for mining a massive sulphide deposit at a depth of 1600 metres in the Bismarck Sea off Papua New Guinea using three remote-controlled underwater vehicles, and even had the machines built. The fleet consists of a shaper to level the seabed, a bulk cutter (the main mining vehicle) and a collector.
However, experts doubt that all three of these vehicles can be deployed feasibly at one time. The area of the targeted ore deposit, with a diameter of a few hundred metres, is relatively small. Moreover, the deposit is cone-shaped. This means that its area decreases in size with increasing depth, which would severely limit the mobility of the mining machines. The specialists see a further obstacle in the presence of hard volcanic rocks in the vicinity of the massive sulphides, which would have to be removed. Nautilus Minerals wanted to use a roller-bit technology for this, but experts believe that this procedure would be very difficult. Nevertheless, the Japan Oil, Gas and Metals National Corporation (JOGMEC) is pursuing a similar approach. In 2017 the company carried out an initial successful mining test for sulphides in the Okinawa Trough in Japanese territorial waters. Plans for undersea mining in the Okinawa Trough foresee an annual production of 1.3 million tonnes of ore following additional multi-year development and testing phases.
- A consortium of German companies comprising Harren & Partner, Combi Lift and Bauer is counting on a single piece of equipment to mine massive sulphides. Their designers are developing a vertical mining system that works on the same principle as diaphragm wall cutters, like those used for rectangular foundations in underground construction, but also in pipeline, harbour and canal construction. The vertical cutter consists of a steel frame with counter-rotating cutting-wheel drums on the underside. This kind of design has already been used successfully in the sea to mine diamonds at a water depth of 165 metres.
With this method, the need for removal of the associated volcanic rocks in projected sulphide mining could be largely avoided and more focus given to production of the ore. The technology would make it possible to cut several dozen metres deep into the massive sulphides at selected locations, thus leaving a very small footprint of only a few square metres at each site on the sea floor. Specialists would therefore expect a much smaller environmental impact. For example, there would be a minimal amount of drill cuttings or tailings released onto the sea floor. It would allow a more focussed mining of the ore on the sea floor without causing a significant suspension plume. Moreover, the installation of a vertical conveyor pipe would be eliminated, and with it the environmentally risky transport from the deep water to the surface. However, the earliest possible test-scale trials of a prototype of this device are planned for 2026 at a water depth of 2400 metres in the German contract area in the Indian Ocean.
Technical development not yet completeIn theory, all of these technical mining concepts may sound comparatively straightforward and achievable, but in practice the technology has to overcome a myriad of challenges over the long term. These include, among other things, water pressures of 400 to 600 bars and ambient temperatures near the freezing point at the deep-sea floor, as well as corrosive salt water. In addition, the cutters, nodule collectors and conveyor systems would have to operate for long periods of time without maintenance because bringing them to the sea surface for repairs would involve considerable expense.
All of the test operations so far have been carried out with prototypes at a reduced scale. For production at an industrial scale, mining machines four to five times as large will have to be built and tested. Methods for the metallurgical processing of manganese nodules and crusts are also still in the early stages of development. For the first time in the world, a concept for the complete smelting and utilization of manganese nodules has been developed by scientists from Germany’s Federal Institute for Geosciences and Natural Resources and RWTH Aachen University, and has already been tested successfully on an expanded laboratory scale. The project partners are presently working to convert the process to an industrial scale. The initial objective is to demonstrate the feasibility of virtually residue-free metallurgical processing and, secondly, they want to find out what a smelting plant would have to look like, and how expensive it would ultimately be to actually extract all the materials contained in the manganese nodules and process them into marketable intermediate products.
Present estimates suggest that the costs of preparation and processing of the nodules would probably make up about one-half to two-thirds of the total investment and operating costs of a deep-sea mining project. The investment costs would amount to around USD 1.5 billion, a sum that is on the order of that required for the development of land-based deposits. The operating costs are estimated at USD 160 to 400 million per year, which means that deep-sea mining is probably not economical today with the current world market prices for metals. The increasing demand for raw materials, however, should cause a long-term rise in prices. Due to these financial aspects and the technological uncertainties set out above, experts believe that it will take at least another five, but more likely ten years before marine mineral resources can be mined on a large scale for the first time. How realistic this assumption is remains to be seen.
Progress or dirty business?The increasing technological feasibility of marine mining has rekindled the dispute over the desirability and sustainability of extracting ore deposits from the sea. Proponents argue that the resource requirements of humankind are increasing enormously as a result of the transition from fossil fuels to renewable energy (electricity storage, e-mobility). If states do not satisfy this demand, it will put their economic development and the prosperity of their populations at risk. In order to meet the demand for raw materials, the existing mining facilities on land would have to be expanded or new mines opened.
- 5.13 > The brittle star Amphiophiura bullata is one of several new deep-sea species that researchers have discovered in the Clarion-Clipperton Zone in recent years. Genetic analyses have revealed that some of the previously unknown brittle stars belong to new ances tral lineages that have evolved in the deep sea over more than 70 million years.
- Either of these options would have immense environmental impacts. Supporters of deep-sea mining therefore point out that:
- For deep-sea mining it would not be necessary for forests to be cleared, groundwater levels to be lowered, or people to be resettled or displaced. Furthermore, there would be no need for costly infrastructures such as roads, power lines, buildings and dewatering systems;
- No large tailings piles would be generated because the ore deposits are directly accessible, and there would be no need to remove tonnes of overburden material;
- With deep-sea mining no pollutants or heavy metals would be released, a problem that often leads to severe environmental damage in the mining of ores on land;
- Deposits in the deep sea, such as manganese nodules, often contain three or more metals in economically viable quantities, so that a number of materials can retrieved from a single site. On land, different deposits have to be excavated for each individual metal;
- The mining of raw materials in the sea can only be carried out by machines. Compared to mining on land, there would thus be significantly less risk for mine workers. Child labour, which is especially common in developing countries, would not occur;
- Mining the marine deposits would help to diversify the currently increasingly concentrated sources of supply on the international commodity markets. For many metals, a large proportion of production comes from a single country, some from politically unstable or undemocratic states that use their market power for political leverage. Resources from the deep sea would mitigate dependency on these nations, because their extraction from international waters is subject to international law and thus to control by the international community.
Impacts on the marine environmentAfter 30 years of research, a lot has been learned about the possible consequences of deep-sea mining for species diversity and biological assemblages on the seabed, although researchers still do not completely understand the functioning of deep-sea ecosystems and their role in the many services provided by the sea. There are a plethora of mobile and sessile organisms living on and beneath the sea floor, including in those areas rich in manganese nodules. They range in size from nematodes, which are only a few tenths of a millimetre long and make up the largest share of species diversity, to sea cucumbers and metres-long fish. Sponges and deep-sea corals grow on the nodules and provide a source of food and protection for many other animals.
Who lives where on the sea floor depends on the particular conditions at a given location. In the German contract area of the Clarion-Clipperton Zone, for example, the sedimentological and geochemical conditions on the seabed can change within a distance of less than 1000 metres. In addition, the expansive deep-sea plain is punctuated by seamounts and ridges. The associated biotic communities are adapted to the local conditions.
The diversity of life in the deep sea is much greater than was previously believed. In recent years, scientists have been able to identify and describe numerous species from the Clarion-Clipperton Zone. In addition, through the use of molecular genetic investigation techniques, they have also succeeded in obtaining an initial impression of the diversity of deep-sea organisms. This is so huge that it is often compared with the species diversity of rainforests. However, the population density of most of the individual species on the sea floor is low, which is why only an estimated ten per cent of the smallest organisms (meiofauna, benthic organisms from 0.32 to 1.0 millimetres in size) and 30 per cent of the mid-sized animals (macrofauna, body size from two to 20 millimetres) have been scientifically described so far.
- 5.15 > Octopuses are one of the many deep-sea inhabitants that are directly dependent on manganese nodules. They attach their eggs to sponges that grow on the manganese nodules.
- On the other hand, the conditions that deep-sea inhabitants have adapted to, which are very inhospitable from a human point of view, are well known. Food is only sporadically available, the water pressure is immense, and temperatures are low. It is also pitch dark 24 hours a day. Most organisms feed on the few particles that sink down from the upper layers of the sea. The consequences of the paucity, and especially of the short-term availability of food following the sinking of plankton blooms at the surface, are that the animals grow slowly on the sea floor, reproduce very late in life, and under some circumstances have extremely long cycles of brooding.
In the period from 2007 to 2011, for example, US American scientists observed a female deep-sea octopus of the species Graneledone boreopacifica off the coast of California whose offspring hatched from the eggs after it had guarded its clutch for four and a half years. Soon thereafter, German deep-sea researchers were able to verify that deep-sea octopuses in the Peru Basin laid their eggs directly on manganese nodules. The animals had attached their eggs to sponges growing on the manganese nodules at a water depth of about 4000 metres.
In the eastern part of the Clarion-Clipperton Zone, other researchers have determined that around one of every two deep-sea inhabitants larger than two centimetres (megafauna) is dependent on manganese nodules because these present virtually the only firm substrate onto which sponges, corals and other sessile organisms can attach. If the nodules were to be removed by giant mining machines, there would no longer be a substrate for recolonization unless restoration measures were carried out to replace the nodules with other solid objects. European researchers are presently carrying out a series of experiments to test the feasibility of these kinds of measures.
Larger organisms are comparatively rare in the Clarion-Clipperton Zone. Researchers calculate just 0.5 animals per square metre of seabed area. The smallest animals, which live mainly within the sediment (microfauna, smaller than 0.3 millimetres), are much more abundant. With an average density of around 300,000 organisms per square metre, they represent the greatest proportion of animals by far. During mining, however, not only the nodules themselves would be removed, but also the upper ten centimetres of the seabed, along with all of the organisms living on it or in it. How long it would subsequently take for nature to recover from this massive intervention is poorly understood.
- Using so-called disturbance and recolonization experiments, scientists have been able to show that interventions in deep-sea life result in long-lasting, but extremely variable changes in the abundance and species composition of animals. In 1989, in order to simulate manganese nodule mining, scientists ploughed up the deep-sea floor across an area of a few square kilometres in the Peru Basin with a harrow. They returned 26 years later to investigate the life in and on the ploughed seabed. They found that the traces of ploughing were still very visible. Surprisingly, the biogeochemical conditions in the sea floor had been altered to such an extent that even the microorganisms able to live there were still severely impacted and, according to predictions, would need at least another 50 years to even approach a state of full recovery.
An overview study from the Clarion-Clipperton Zone also concluded that, following an intervention, some of the species living in the sediment will return to the area relatively soon, meaning within a few months to years, and that their numbers even exceed the original abundance, while other species require decades to recover. Experts therefore contend that the resettlement of disturbed areas can take many generations. The composition of the biotic community on and in the seabed remains altered for decades after the event, although research results from one kind of area cannot be extrapolated – neither to other deep-sea regions nor to other types of marine mineral deposits (sulphides, crusts).
In addition to the stripping of the top layer of the seabed, however, experts expect to see other kinds of environmental impacts from the mining methods that have been developed for manganese nodules. For one, there would be disturbances caused by the noise, the vibrations and the bright lights of the giant excavation machines. For another, as a result of the collection of manganese nodules and the processes for cleaning and transporting the ore, clouds of sediment or turbidity can be expected to form, mainly near the sea floor but also higher in the water column. Researchers expect that the hydraulic nodule collectors now being built will stir up 500 to 1000 tonnes of sediment from the sea floor per hour. This amount of material will be extremely problematic when it settles back onto the surface. Under natural conditions, sedimentation rates in the deep sea are only a few millimetres per 1000 years. But the agitation from nodule mining would cause a drastic increase in this rate.
- From experiments and computer calculations it has been determined that 90 to 95 per cent of the sediment churned up by the mining machines would be redeposited quickly within a radius of up to ten kilometres. However, the newly formed sediment surface has a completely different structure and composition than the original sea floor, and thus no longer resembles the former natural habitat. The remaining particles are carried away by ocean currents and deposited outside of the mining area. Experts believe that industrial mining of the manganese nodules will lead to significantly higher sedimentation rates as far away as 20 or 30 kilometres.
The impacts that these turbulence clouds and sediment deposits will have on the biotic communities of the deep sea probably vary from species to species, and have not yet been thoroughly researched. Initial investigations indicate that microorganisms in the sediment can tolerate up to about one additional centimetre of cover by resuspended sediment. If this sediment layer is thicker, very few animals will survive. Sessile animals like sponges and corals, which live on the sea floor close to the mining area and filter the otherwise very clear bottom water to obtain food, will be covered by the masses of sinking sediment particles and have very low chances of survival. But octopuses, fish and the larvae of many other deep-sea species could also suffer under the clouds of sediment. In addition, scientists cannot rule out the possibility that the turbidity clouds caused by deep-sea mining could be detrimental to fisheries.
- Basically, then, the bottom line for science is this: Because no deep-sea mining has yet been carried out at an industrial scale, and there is a lack of relevant accompanying studies, no dependable conclusions can be drawn regarding the true intensity and duration of the disruptive intervention, nor about its long-term consequences for the biotic communities of the deep sea. Therefore, the only option for regulatory bodies such as the Internatio-nal Seabed Authority is to introduce regulations at the outset that limit the consequences as far as possible. Minimizing large-scale consequences will require the development of low-impact equipment and careful and adaptive territorial planning for mining areas. The current level of knowledge, however, is not sufficient to allow effective protective measures to be taken. Many areas of the deep sea can be considered as still undiscovered. Furthermore, no one can say with certainty exactly what role the deepest layers of the ocean play in the many mass cycles of the sea, and thus ultimately for the Earth’s climate processes.
The International Seabed Authority addresses this lack of knowledge by requiring compliance with the precautionary principle and the highest environmental standards, and by establishing regional environmental management plans. For the protection of species diversity in the Clarion-Clipperton Zone, it has also created nine protected areas on the sea floor of 160,000 square kilometres each, which constitute around 30 per cent of the total area. However, it has not yet been scientifically proven that their size, location and species diversity would be sufficient for the recolonization of potentially disturbed mining areas. For this reason, the Legal and Technical Commission of the ISA is now discussing whether an additional three or four protected areas should be established that encompass habitats previously not considered. In addition, international negotiations are being held to determine where appropriate protected zones should be established for all other areas of the high seas that are rich in resources, and what obligations these would carry for the contract holders. The primary goal is to create binding regulations for careful and adaptive territorial planning for deep-sea mining, and provide effective environmental protection measures on a regional level.
Criticism of the International Seabed AuthorityEnvironmentalists, however, doubt that the International Seabed Authority can justly fulfil its diverse roles as contractor, mining facilitator, fee collector and top-level inspection and environmental protection body. The ISA bodies, but particularly its key organ, the Legal and Technical Commission, which is responsible for legal and science-technology questions, are very insufficiently funded and too understaffed in the field of environmental expertise to be able to properly carry out their tasks. Moreover, there are fundamental conflicts of interest within the agency resulting from the various requirements. For example, how can an agency be expected to effectively protect the environment when at the same time it is evaluated based on the extent to which it enables deep-sea mining?
The environmental organization Greenpeace accuses the ISA of issuing exploration contracts to various companies that are acting on behalf of only a few corporations from industrialized countries. The subsequent deep-sea mining in international waters would thus preferentially benefit these companies. The burden of the many risks associated with mining, on the other hand, would be carried mainly by the developing countries. For one reason, this is because they act as the Sponsoring States for private mining companies and, for another, because large ore deposits lie within their national waters. Although the ISA cannot make decisions about the mining of these, conceivable damages such as the collapse of ecosystems or the impacts on fisheries would mainly affect the coastal populations of these countries.
Other experts dispute Greenpeace, saying that there are currently no private investors in massive sulphides and ferromanganese crusts, and that about half of the manganese nodules are also state-held contracts involving both industrialized and developing countries. Companies that want to carry out mining in international waters also have to be insured against environmental damage and pay into an environmental compensation fund. With respect to the criticism of the ISA, it should be noted that the Authority itself calls upon all member states to send additional specialists to strengthen the Commission’s environmental expertise.
These experts also praise the international cooperation within the ISA and the progress that the Seabed Authority has made in recent years. In July 2000 the legal foundations for prospecting and exploration of manganese nodules were adopted. This was followed in May 2010 by the regulations for massive sulphides and in July 2012 by those for ferromanganese crusts. Since July 2016 the ISA member states have been negotiating mining regulations that will become a component of the Mining Code, an overarching set of regulations for the exploration and industrial mining of mineral resources, which, in the view of many observers, offers the rare opportunity to establish science-based environmental protection measures prior to the actual mining activities.
- he Mining Code regulates the formal aspects of proposal submission, protection of the environment through environmental impact statements, including environmental management and monitoring, as well as public involvement, occupational safety, monitoring of mining activities by inspectors, and the shutdown plans. In addition, the regulations shall spell out what fees and compensation payments the mining companies must pay to the ISA when they extract raw materials from international waters and privately profit from the common heritage of mankind. Directly related to this is the question of how the potential income could be fairly distributed to all countries. The Convention on the Law of the Sea contains an important clause that says raw material mining in the sea may not be detrimental to production on land. If one or more nations do incur a disadvantage due to deep-sea mining, perhaps because it causes a decline in raw-material prices or their ore deposits are no longer exploitable and the state loses income in the form of taxes, then according to the Law of the Sea they must be compensated by the ISA. How and by whom has also not yet been completely clarified.
Circular economy plus X – the better alternativeOnly the future will tell whether industrial deep-sea mining will someday become a reality. Environmentalists demand a general ban and comprehensive protection of the deep-sea environment. The arguments of businesses and governments, on the other hand, are based on the rising demand for raw materials and the need to secure the supply of these and the jobs that depend on their respective industries.
Added to all of this, there is also the fear that individual resource-rich nations will gain excessive market power and use it to exert political leverage. One conceivable solution to this dilemma entails a combination of different strategies, based on the premise that the global economic system and consumer behaviour could be fundamentally altered and no longer based exclusively on growth and consumption.
To start with, this would require adoption of a sustainable circular economy. Among other things, this presupposes that:
- there are sufficient metals within the circular economy to meet demand;
- products undergo further development so that as little mineral resources as possible are used in their production;
- goods and products have high durability and a long lifetime;
- all end-of-life devices and the materials they contain are recycled and reused.
- 5.17 > These pictures show two of the coral atolls in the South China Sea that China has transformed into islands using sand replenishment. Both the Fiery Cross Reef (above) and the Subi Reef have served as military stations since 2017. The atolls have been largely destroyed as habitats for corals and associated reef dwellers.
- Circular systems not only preserve the environment, they also have economic advantages. Through the recycling of metallic waste and scrap, the amounts of raw materials extracted by mining would be reduced and a great deal of energy saved in production. The mountains of waste would stop growing. Furthermore, many metals can be recovered with no loss in quality.
Worldwide today, recovery rates for materials such as iron, zinc, copper, gold and silver already reach 50 to 90 per cent. With many other metals there is great potential to improve recovery rates. However, it is also a fact that electronic products and their resulting scrap continue to become more complex, which makes the recycling of individual materials more difficult and in some cases no longer economical. Furthermore, a circular economy can only function if the amount of materials recovered is sufficient to cover worldwide demand.
Experts believe, however, that, in view of rapid population growth and increasing technological transformation around the world, the need will remain for metallic raw materials to be extracted from natural deposits in the future. On the other hand, the supply situation could be improved by a more thorough development of deposits.
Given this background, a few years ago the European Commission contracted scientists to determine the amounts of valuable minerals and metals that might still be present in the tailings of former mines or strip mines, and how they could be extracted in future.
Their results indicated that the probability of finding raw materials such as chromium, niobium or vanadium in the tailings piles is great, particularly because land-based mining in the past has always concentrated on the production of only one or two resources. However, it must be considered that some effort would be required to recover the metals and minerals that were previously not recognized as important. Methods by which various materials are all extracted at the same time are the most sensible, even though these kinds of processes are generally very energy-intensive.
Other researchers are searching for ways to directly extract dissolved metals from sea water. For example, there is an estimated 180 billion tonnes of lithium stored in the ocean. But the actual concentration of this metal in sea water is only 0.2 parts per million. In order to extract this very minor amount, scientists employ specially coated electrodes, which they repeatedly subject to an electric current. As a reaction to the electric current, the lithium ions migrate out of the water into the electrode. This method works in an experimental setting, but it is still far from being applicable on an industrial scale.
- For this reason, in 2017, a number of German scientists posed the question of whether it would be conceivable to search for ore deposits in the subsurface of the shallow, near-coastal shelves before undertaking deep-sea mining, which is technically more complex and fraught with serious consequences. The seabed of the continental shelf is merely an extension of the continent, which could mean that metal or mineral deposits occurring on land near the coasts also extend out onto the sea floor. These nearcoastal resources could probably be extracted comparatively easily, and with significantly less risk, than the ore deposits in the deep sea.
For example, geologists have predicted the presence of large gold deposits off the west coast of Africa, nickel deposits in the Arctic Ocean and lead-zinc deposits in the Gulf of Mexico and Mediterranean Sea. In many of these regions resource extraction would not be a new concept. In several shelf seas, oil and natural gas have been produced for more than 70 years. In other coastal areas, sand and gravel are being extracted, albeit with serious consequences for the sensitive coastal marine ecosystems.
This means that as long as demand continues to rise and truly sustainable alternatives are lacking, the extraction of mineral resources will always be a matter of balancing interests, posing the question of how the benefits compare to the somewhat unforeseeable consequences to the environment and people. The international community is now, for the first time, faced with the decision of whether industrial mining should actually take place in the international deep sea.