In a world with a growing population the need to achieve climate policy goals as well as the UN sustainable development goals, primary mining for raw materials will continue in the coming decades. In the long term, recycling of metal stocks and a circular economy represent the most promising and responsible solutions and will help to eliminate the environmental and social impacts caused by mining. However, the metal quantities needed for this purpose are not available due to their long-term use. It will take decades to build up the primary stock of metals that will allow the foreseen demand to be met sustainably via recycling and a circular economy. Companies, politicians, and the media are therefore discussing possible substantial contributions from the oceans to meet the future demand for metallic raw materials, not only for this systematic change, but also for reasons of security of metal supply.
Marine minerals such as manganese nodules, Cobalt- (Co-)rich ferromanganese crusts, and seafloor massive sulfides are therefore commonly seen as the possible future resources that could, in combination with intensified recycling, provide the additional metals necessary for a clean energy transition and to reach the climate goals. As exploration activities in the oceans are increasing, cobalt, nickel, copper, rare-earth and other elements from the deep sea could enter supply chains within the decade. Whether they should is the subject of vigorous debate. Scientists and non-governmental organizations have raised concerns about the lack of a regulatory framework and environmental baseline studies and the limited knowledge of the potential environmental impacts of deep-sea mining. These concerns have resulted in calls for a moratorium on deep-sea mining by, e. g., the World Wide Fund for Nature (WWF) and the Deep Sea Conservation Coalition, until certain conditions are met. Others, such as Greenpeace, call for a ban on deep-sea mining altogether. As a consequence of this beginning debate, companies such as Samsung SDI, the BMW Group, and the Volvo Group have committed not to use metals sourced from deep-sea mining until the environmental risks are comprehensively understood.
2 The resources
Manganese nodules are mineral concretions that consist of manganese and iron oxides (1). They occur widely on the vast, sediment-covered, abyssal plains at water depths of about 3,000 to 6,000 m. The manganese and iron minerals in these concretions form by a combination of hydrogenetic growth, in which the minerals precipitate from cold ambient seawater, and diagenetic growth, in which they precipitate from porewaters within the sediment. The greatest concentrations of metal-rich nodules that have been discovered so far occur in the Clarion-Clipperton Zone (CCZ) of the eastern Pacific Ocean (Figure 1). Nodules are also known to be concentrated in the South East (SE) Pacific (Peru Basin), near the Cook Islands, and the Indian and Atlantic oceans.
Cobalt-rich ferromanganese crusts precipitate onto nearly all rock surfaces in the deep oceans that, due to bottom currents, are free of sediment. They form pavements of manganese and iron oxides on the flanks of volcanic seamounts, ridges, guyots, and plateaus in water depths ranging from 400 to 7,000m (1). Crusts with sufficient thickness and metal content to be of economic interest commonly occur at depths of about 800 to 2,500 m. Currently most of the economically interesting Co-rich ferromanganese crusts have been observed in the western Pacific, the so-called Prime-Crust-Zone. However, a few occurrences of crusts with exceptional metal contents have also been found in the Atlantic.
Seafloor massive sulfides deposits form from high-temperature fluids emitted as a consequence of the interaction of seawater with a heat source (magma) in the sub-seafloor at active volcanoes such as those along the global mid-ocean ridges. During this process, cold seawater penetrates through cracks in the seafloor, reaching depths of several kilometers into the crust, and is heated to temperatures above 400 °C (2). The chemical reactions that take place during this process result in a hot, metal-rich fluid. Due to the lower density, this hot fluid rises rapidly to the seafloor, where the dissolved metals precipitate upon mixing with cold seawater, forming a dispersing plume as well as metal-rich chimneys and mounds. Such sulfides have been found in water depths ranging from a few hundred meters to > 5,000 m. Most of the known sulfide occurrences are small and therefore not of economic interest, but certain geological conditions especially along slow-spreading mid-ocean ridges and in volcanic arcs associated with subduction zones seem to host larger deposits. Exploration work globally is currently focusing on inactive sulfide deposits as they lack the chemosynthetic faunal communities present at active sites that will likely be protected by the upcoming regulation framework of the International Seabed Authority (ISA).
At present, a proper global assessment of the three resources is not possible due to a severe lack of information regarding their size, distribution, and composition. It is clear, however, that manganese nodules and Co-rich ferromanganese crusts are a vast resource and mining them could have a profound impact on global metal markets, whereas the global resource potential of seafloor massive sulfides appears to be small. The deep-sea mineral commodities are formed by very different geological processes resulting in deposits with distinctly different characteristics. The geological boundary conditions also determine the area that will be affected by mining. Similarly, the sizes of the most favorable areas that need to be explored for a global resource assessment are also dependent on the geological environment (2).
3 Exploration status in areas beyond national -jurisdiction
At present the ISA, responsible for administering seafloor resource in areas beyond national jurisdiction (ABNJ, “the Area”), has issued 35 fifteen-year contracts for exploration (Figure 1). Nineteen contracts are for the exploration of manganese nodules, mainly in the CCZ of the Eastern Equatorial Pacific (17; covering 1.2 M km2), but also one each in the western Pacific (74,000 km2) and the Central Indian Ocean (75,000 km2). Of the 19 contractors, eight are government bodies while the remaining eleven are commercial entities sponsored by states. In the first nine years of licensing, until 2011, only national institutions applied for exploration contracts in the Area, but since then only commercial entities backed by state parties made applications. Contracts for the exploration for seafloor massive sulfides, covering 10,000 km2 each, are currently issued to national institutions for areas along the Mid-Atlantic Ridge (3) and in the Indian Ocean (4). The remaining five contract areas, all with national institutions and covering 3,000 km2 each, are for the exploration for Co-rich ferromanganese crusts and are located in the Western Pacific (4) and the -Western Atlantic (1).
4 Other global activites
In addition to the work performed by the various contractors to the ISA, the last years have seen intensified exploration within the exclusive economic zones of selected countries. In some cases these activities were also met by substantial funding for technology development. In Japan, a multi-year R&D project on marine mineral resources that was extended in 2014 into a project on next-generation technology for seabed exploration (3). Within this project successful mining tests were performed at seafloor massive sulfide occurrences in the Okinawa Trough in 2012, 2015, and 2017.
In recent years, Norway has engaged in deep sea exploration within their EEZ through activities of the Norwegian Petroleum Directorate and is reported on planning to open its EEZ for exploration licenses as early as 2023 (4).
In Europe several large scale research projects targeted marine minerals: the Blue Mining Project (2015 to 2018, EU grant agreement no. 604500; https://bluemining.eu) was focused on technology developments for exploration, while the MIDAS Project (2013 to 2016, EU grant agreement no. 603418; www.eu-midas.net) investigated the various impacts of deep-sea mining. The European Joint Programming Initiative (JPI) Oceans specifically addresses the ecological aspects of deep-sea mining for manganese nodules through the “Mining Impact” projects 1 and 2 (2015 to 2022).
On the commercial side, Nautilus Minerals Inc., a company formerly holding a mining license in the territorial waters of Papua New Guinea and long aiming to become the first to mine seafloor massive sulfides, was delisted in 2019 from the Toronto Stock Exchange. Its famous Solwara 1 project and other assets were acquired by Deep Sea Mining Finance and the future of this operation is unclear.
5 German activities
Germany through the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) holds two exploration license areas in the Area: one in the eastern Pacific for manganese nodules (Figure 2) that was signed in 2006, and one for polymetallic sulfides in the Central Indian Ocean (Figure 3) signed in 2015. Both licenses are valid for 15 years. A proposal for extending the exploration contract for manganese nodules for another five years has been submitted to ISA.
5.1 Work in the CCZ
The German license for manganese nodules covers approximately 77,000 km2. Over the years BGR, together with its many research partners has performed nine research cruises and addressed questions regarding resource assessment as well as on acquiring environmental baseline data. Most of the work concentrated in the eastern area. With respect to the geological resource BGR has assessed the exploration area with various technologies including ship-based multibeam echo sounding and backscatter mapping, intense nodule sampling, video surveys using towed camera sleds as well as autonomous underwater vehicles, and geochemical analyses of the nodules (5). The results have been used to assess the variability of the nodule abundance and nodule size and to investigate the underlying responsible processes. In regions with a generally high abundance of large nodules a number of so-called prospective areas (PA) have been delineated for which resource estimates will be published soon.
Important methodological steps were the use of ship-based backscatter information for the delineation of areas covered with manganese nodules (6) and the development of an automated and reliable detection of manganese nodules in seafloor images that is able to analyze the vast amounts of bottom photos retrieved during surveys (7). However, comparison between the box corer samples and the automated analysis of the images revealed a consistent underestimation of the nodule abundance preventing this method of being useful for resource assessment (8). Nevertheless, continuity of the manganese nodule abundance was shown with the video surveys.
One of the major hurdles of the economic utilization of manganese nodules lies in the processing of the fine-grained and complex polymetallic ore. Already in the 1970s, the International Nickel Corporation (Inco) proposed the so-called Inco-process to utilize polymetallic deep-sea nodules as a resource for nickel, copper and cobalt. The process is based on standard metallurgical processes where the valuable metals nickel, copper and cobalt are concentrated in an early stage of the process and manganese is mainly discarded in the slag. Today, contractors favor a full utilization of the metals in the nodules by including manganese and the slag into the product line (zero-waste). Over the past years BGR, together with its partners at the TU Clausthal University and RWTH Aachen University, has optimized the processing of manganese nodules in order to develop such a zero-waste process. The processing is based on a modified pyrometallurgical process followed by hydrometallurgical processing of the alloy (9). The processing is still in the lab-scale and further work is needed to upscale to industrial scale. Similar investigations into processing are being done by other contractors to the ISA.
Data such as nodule distribution, metal content, and topography from the German license area has also been used to develop spatial planning tools for mining concepts (10) and resulted in the delineation of possible mining designs for future nodule mining (11).
Germany is currently not involved in the construction and development of collectors for seabed mining. In this respect, contractors such as the Belgian GSR, Korea, India, and China are much advanced. During its most recent campaign in the spring 2021, BGR and scientific partners from the JPI Oceans project “Mining Impact 2” are, however, involved in the environmental impact studies around the trial of the nodule collector Patania II within the German and Belgian license area. During this trial a collector of a quarter of the full-size mining collector is being tested and the impacts are being monitored by an independent international research team.
5.2 Work in the INDEX area
The second license area assigned to BGR consists of 100 blocks of 10 km x 10 km and covers nearly 1,000 km of the Central Indian Ridge and Southeast Indian Ridge (Figure 3). Since the contract for exploration work for seafloor massive sulfides between BGR and ISA was signed in 2015, a series of cruises was performed nearly annually to investigate the license area. It has to be noted that BGR has to return 50 % of the license area back to the ISA by 2023 as part of their contract. In addition to ship-based seafloor mapping of the entire license area, regional geophysical data (magnetics, gravity) and local, high-resolution data (electromagnetic, magnetics, acoustic) has been collected. The water column has been intensely studied by various tools, including surveys for the detection of hydrothermal anomalies in the water column. Bottom photos and samples were collected by a suite of instruments including remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs) and towed platforms. Over the years BGR has developed a unique set of tools for the exploration for massive sulfides including the electromagnetic profiling tool GOLDEN-EYE, and the towed sensor platforms HOMESIDE and SOPHIE (5). During the surveys, numerous new active and inactive hydrothermal fields have been found many of them with the recently developed geophysical exploration tools (12).
Many of the datasets and samples obtained by BGR are intended to provide environmental baseline data needed under the contract with ISA. Since the beginning of BGR’s activities in the Indian Ocean in 2011, baseline studies for biodiversity, sedimentation, ocean currents and others represent an important and integral part of the activities.
As with manganese nodules, BGR is also investigating the optimization of ore processing for massive sulfides, currently on a lab-scale (13).
6 Requirements for economic mining
The decision to commence mining of any of the deep-sea commodities discussed here will depend on the availability of metals from terrestrial sources and their price in the world market, as well as the techno-economic analysis based on capital and operating costs of the deep-sea mining system and the processing costs. In addition, there are still technological hurdles to overcome before full-scale deep-sea mining equipment can even be tested. Finalizing the exploitation guidelines by the ISA is yet the prime prerequisite for establishing dee-sea mining in the Area. Discussions and stakeholder consultations have been ongoing for years and there is hope to have the regulations in place by 2022 or 2023. If deep sea mining regulations by ISA are put in place in the coming years, and if society provides the social license to mine the deep-sea, metals sourced from the seafloor could be part of many consumer products very quickly. This could actually pose further threats on contractors, as due diligence guidance for responsible supply chains of metals, such as those provided by the OECD could impact their activities. Such guidelines are likely to become a cornerstone of responsible mineral sourcing globally (14). Existing due diligence and responsible sourcing standards and tools are designed for land-based mining only and it may require substantial adaptation before they can be applied to the deep sea.
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(2) Petersen, S.; Krätschell, A.; Augustin, N.; Jamieson, J.; Hein, J. R.; Hannington, M. D. (2016): News from the seabed – Geological characteristics and resource potential of deep-sea mineral resources. In: Marine Policy 70, pp 175 – 187.
(3) Urabe, T.; Ura, T.; Tsujimoto, T.; Hotta, H. (2015): Next-generation technology for ocean resources exploration (Zipangu-in-the-Ocean) project in Japan. OCEANS 2015, Genova, 2015, pp 1 – 5.
(4) Reuters 2021-01-12: Norway eyes sea change in deep dive for metals instead of oil. Accessed on January 13th, 2021.
(5) BGR (2018): Marine Rohstoffe Newsletter 2018. Marine Mineralische Rohtsoffe an der BGR. 9 pp.
(6) Knobloch, A.; Kuhn, T.; Rühlemann, C.; Hertwig, T.; Zeissler, K.-O.; Noack, S. (2017): Predictive Mapping of the Nodule Abundance and Mineral Resource Estimation in the Clarion-Clipperton Zone Using Artificial Neural Networks and Classical Geostatistical Methods. In: Sharma, R. (Ed.), Deep-Sea Mining, vol. 122. Springer International Publishing, pp 189 – 212.
(7) Schoening, T.; Kuhn, T.; Jones, D. O. B.; Simon-Lledo, E.; Nattkemper, W. (2016): Fully automated image segmentation
for benthic resource assessment of poly-metallic nodules. In: Methods in Oceanography 15-16, pp 78 – 89.
(8) Kuhn, T.; Rathke, M. (2017): Visual data acquisition in the field and interpretation for seafloor manganese nodules. EU Project Blue Mining (GA No. 604500) Delivery D1.31. www.bluemining.eu/downloads, 34 pp.
9) Sommerfeld, M.; Friedmann, D.; Kuhn, T.; Friedrich, B. (2018): “Zero-Waste”: A Sustainable Approach on Pyrometallurgical Processing of Manganese Nodule Slags. In: Minerals 8, 544 – 13.
(10) Volkmann, S. E.; Kuhn, T.; Lehnen, F. (2018): A comprehensive approach for a techno-economic assessment of nodule mining in the deep sea. In: Mineral Economics 31, pp 319 – 336.
(11) Volkmann, S. E.; Lehnen, F. (2018): Production key figures for planning the mining of manganese nodules. In: Marine Georesources & Geotechnology 36 (3), pp 360 – 375.
(12) Müller, H.; Schwalenberg, K.; Reeck, K.; Barckhausen, U.; Schwarz-Schampera, U.; Hilgenfeldt, C.; von Dobeneck, T. (2018): Mapping seafloor massive sulfides with the Golden Eye frequency-domain EM profiler. In: First Break 36, pp 61 – 67.
(13) BGR (2019): Marine Rohstoffe Newsletter 2019. Marine Mineralische Rohstoffe an der BGR. 13 pp.
(14) World Economic Forum (2021): Deep-Sea Minerals: Why Manufacturers and Markets Should Engage Now, 2021. Briefing Paper April 2021, 17 pp.