Perspectives on Deep-Sea Mining

The seeds of deep-sea mining were sown during the post-war boom. The massive use of raw materials and the wholescale destruction of both property and material during that war created a demand for raw materials that some thought could not be met from conventional sources. Amongst these was a group of University of California Professors who met at the Scripps Institution of Oceanography in 1957 and who initiated a programme on the evaluation of mining manganese nodules (Mero 1965). John Mero was appointed Chief Investigator of this project and went on to produce several papers on the subject (Mero 1959, 1960, 1962), and his now-classic book ‘The Mineral Resources of the Sea’ (1965) painted a very optimistic picture of deep-sea mining.

It was arguably the publication of Mero’s book that initiated interest in the whole business of deep-sea mining. However, Mero was not the first person to recognise the future potential of manganese nodules. John Young Buchanan, ship’s chemist during the Challenger Expedition (1873–1876) mentioned their possible future value in a letter to his father (Glasby 1977). Additionally, Dunham (1964) mentioned the possibility of potentially economic hydrothermal minerals occurring on the seafloor, several years before they were actually discovered.

The deep-sea minerals of interest in this Introduction are manganese (polymetallic) nodules, cobalt-rich ferromanganese oxide crusts and hydrothermal polymetallic sulphide deposits (PMS).

Deep-sea mineral resources within and beyond the national jurisdictions offer several opportunities for exploration and possible exploitation owing to their potential as alternate source of metals such as Ni, Cu, Co, rare earths and others. These are considered critical for meeting mankind’s increasing demands including that of transitioning to green energy in view of depleting or low-grade terrestrial deposits. Currently, several studies are underway for evaluating the economic and potential benefits of mining the deep-seabed minerals as well as developing suitable technologies for their exploitation, on one hand, and also for assessing the ecological risks, suggesting ecosystem-based management approach and developing relevant regulations for deep-sea mining, on the other. This chapter aims to put into perspective the current status and future prospects of deep-sea mining.

Deep-ocean ferromanganese crusts and manganese nodules are important marine repositories for global metals. Interest in these minerals as potential resources has led to detailed sampling in many regions of the global ocean, allowing for updated estimates of their global extent. Here, we present global estimates of total tonnage as well as contained metal concentrations and tonnages for ferromanganese crusts and manganese nodules using the most extensive compilation of geochemical data collected to date, along with updated boundaries of regions of interest for these minerals. We present results from mean composition calculated in two ways: first, a global flat average of regional mean compositions, and second, a regionally weighted average that considers differences in chemistry among genetic types and/or oceanographic and geologic settings for these mineral occurrences. For nodules, we use the three genetic types: (1) hydrogenetic, typified by nodules from the West Pacific Nodule Field and Penrhyn Basin; (2) diagenetic, typified by nodules from the Peru Basin; (3) mixed hydrogenetic-diagenetic, typified by nodules from the Clarion–Clipperton Zone and the Central Indian Ocean Basin, and Atlantic Ocean regional type hydrogenetic nodules. All crusts considered here are of hydrogenetic origin, which we divide into seven regional types that reflect a combination of ocean basin and other source inputs. Crust types include Arctic Ocean, Atlantic Ocean, Indian Ocean, Continental Margin, Prime Crust Zone (PCZ), North Pacific (non PCZ), and South Pacific. Based on our areal estimates, we find that abyssal regions likely to contain hydrogenetic-type nodules are by far the most widespread in the global ocean (47% of total area), Atlantic Ocean (28%) are next, followed by mixed diagenetic-hydrogenetic (22%) and diagenetic (3%) types. For crusts, the Prime Crust Zone is the most extensive global region (27% of total area) followed by South Pacific (20%), Indian Ocean (18%), North Pacific (12%), Continental Margins (11%), Atlantic Ocean (10%), and Arctic Ocean (2%) types. The global total tonnage estimates that we calculated from this method are 21 × 10¹⁰ dry tons for manganese nodules, within the range of previous estimates, and 93 × 10¹⁰dry tons for ferromanganese crusts, which is 4.5 times higher than the 20 × 10¹⁰dry tons reported by Hein et al. (2003). This geology and oceanography driven approach to marine mineral quantification contrasts with estimates typically carried out for terrestrial mineral resource deposits. Nevertheless, these estimates and the data that support them demonstrate that marine minerals are an impressive repository for global metals.

We review recent results of onsite seabed surveys and geoscientific analyses of hydrogenetic ferromanganese crusts in the northwestern Pacific and attempt to identify the controlling parameters of the diversity of the deposits in terms of scientific understanding of processes and environments to be applied for future deep-sea mining. We ascertained that oxidizing seawater, old and stable rock substrates, and no or scarce sedimentation or productivity, are optimal conditions for high-grade abundant deposits. The following physicochemical and geological processes were verified from our observations and analyses: (1) ultra-slow and fairly continuous growth at a rate of several μm/kyr in all water-depth zones for more than 10 Myr; (2) initial precipitation of poorly crystalline vernadite (Fe/Mn around one with two diffused X-ray diffraction) now forming coccoid-like morphology as a final constituent to comprise the crusts, and (3) the highest Co concentration around the oxygen minimum zone. Moreover, the microstratigraphy of crusts indicates surprisingly similar structural zones, mineralogy, and chemistry on micron- or millimeter-scales among those from remote areas when the water-depth range is the same. Thus, continuity in abundance and grade at the regional scale can be reasonably expected. Geological characterization and consideration are essential for understanding mineral diversity and evaluating the economic potential and distribution.

The fine-scale concentration of platinum in a hydrogenetic ferromanganese crust (Takuyo-Daigo Seamount 2987 m water depth) was determined using secondary ion mass spectrometry (SIMS). The crust was analyzed chronologically, and the spatial resolution of the SIMS depth profiling was 0.013 μm, corresponding to 5 years of the crust growth. SIMS depth profiling is the only feature that is not found in other analytical methods. Platinum (Pt) concentration in vernadite of the crust ranges from 0.14 to 0.31 ppm, and it finely fluctuated along the growth direction. Little Pt was found in a brown matrix that exists among columnar vernadite. Our results showed that SIMS is a powerful and promising tool for Pt microanalysis to understand crust characterization and the environment for selective accumulation of seawater-dissolved Pt into crusts.

Global Sea Mineral Resources NV (GSR) holds an exploration contract with the International Seabed Authority (ISA) established under UNLOS to explore for polymetallic nodules on the seafloor of the Clarion Clipperton Zone (CCZ) in the Pacific Ocean.

The basis of GSR’s research and development (R&D) strategy was developed in 2013 following a desktop study that defined an integrated concept of operation. By performing this integrated study, it was possible to identify all systems and related subsystems and define an overall architectural diagram. A key component of the deep seabed mining system is the seafloor nodule collector (SNC).

The SNC has a significant influence on the overall operational environmental impact and on the achievable production rate, two criteria that are critical in developing a responsible mining operation. Additionally, given commercial deep-seabed mining operations are unprecedented, the SNC is the subsystem involving the highest number of information and knowledge gaps, such as the environmental impacts and effects, its response to soil characteristics, trafficability, and nodule collection methodology.

Hence, from all the systems and subsystems identified, GSR decided to focus its first efforts on the SNC system and more specifically on a pre-prototype of an SNC. This feasibility study, called ProCat (derived from “Prototype Caterpillar”) extended from 2015 to 2021 and consisted of a step-by-step approach and culminated in the design, building, and testing of a pre-prototype SNC, called Patania II (PATII).

Following the successful trials conducted with Patania II at 4500 m water depth in the CCZ in 2021, the final phase will commence, which will culminate in the design, building, and trial of a commercial-scale SNC.

GSR remains committed to responsible deep-sea research and technology development, one step at a time.

The Japan Oil, Gas and Metals National Corporation (JOGMEC) has been working toward developing seafloor polymetallic sulfide deposits. As part of its achievement, in 2017, it successfully tested continuous lifting of ore from the seabed in Exclusive Economic Zone (EEZ) of Japan near Okinawa. It is the first successful attempt in the world for sulfide mining. Furthermore, by the flotation test using 15 tons of ore, 2 tons of the concentrate with a sufficient grade of zinc were recovered and charged into the furnace of the existing domestic smelter. In this chapter, these results and remaining challenges toward the commercialization of the project are discussed.

A review of comparative advantages of mineral processing of deep-sea polymetallic nodules over terrestrial ores is attempted. The work conducted as part of Global Sea Mineral Resources’ onshore processing development strategy has contributed to answer the critical questions related to the choice of the flow sheet, the adequateness of the beneficiation of polymetallic nodules, the behavior of nodules with regard to comminution, and how it compares to land-based ores in terms of energy intensity. The results suggest there is an undisputable environmental advantage associated with the comminution of polymetallic nodules as compared to conventional (monometallic) land-based ores, due to their higher grade, polymetallic character, and comminution behavior.

Assessment of deep-sea polymetallic nodules processing technologies has assumed renewed importance in the context of the current thrust for supply of metals such as Cu, Ni, Co, and Mn that are required for clean energy transition processes. Because of similarity of suggested nodules processing operations to nickel laterite processing from land ores, the energy intensity of the operations is high. Process energy consumption data are scarce although process energy costs have been referred. The chapter elaborates an approach for minimum gross energy estimation (GER) and subsequent CO₂ emissions based on key process steps of existing flow sheets based on both foreground and background processes. For example, for hydrometallurgical processes, estimated emissions for slurry heating may vary between 0.11 T CO₂/T and 0.34 T CO₂/T nodules, with addition of 0.25 T CO₂/T nodules for downstream process using electricity to produce metals and a marketable manganese slag product. Key process emission for pyrometallurgical process is estimated at 0.67 T CO₂/T nodules. The chapter examines the possibilities of lowering such process emissions by replacing fossil fuel-based reductants with less carbon intensive inputs such as methane and renewable hydrogen, recycling CO₂ and other innovative options of using renewable energy. For hydrometallurgical flow sheets, minimizing reagent recycle such as ammonia, use of lower temperature sulfuric acid leach, combination of multiple input reactants are the possible options. Use of grid electricity with lower emission value and use of renewable electricity such as hydropower for meeting electrical energy requirements will play important role in future plant flow sheet design. The chapter provides estimates of energy and emission values for integration of renewable energy options for existing flow sheets. Although there is considerable potential for use of renewable energy for a hypothetical polymetallic nodules plant design, additional data based on industry parallels/experiments need to be generated.

Polymetallic nodules (PMN) are considered to be a potential source of valuable metals such as copper, nickel, and cobalt. Over the last five decades, several processes have been developed to recover these metals with or without recovering manganese. Utilization of this resource has become more pertinent due to the large requirements of these metals for lithium-ion batteries used in electric vehicles besides other conventional requirements. Environmental agencies are enforcing strict regulations for metallurgical and chemical industries to minimize liquid, solid, and gaseous effluents. In fact, presently the emphasis is on zero waste processes. In this chapter, it is proposed to critically analyze the hydrometallurgical reductive ammonia leaching process for the recovery of metal values from nodules. This process comprises ammonia leaching with sulfur dioxide, demanganization of dissolved manganese, copper solvent extraction-electrowinning to obtain copper cathode, bulk sulfide precipitation followed by its dissolution and solvent extraction-electrowinning for cobalt, nickel separation to produce their respective cathodes. In this chapter, we look into the effluents generated in this process and critically analyze the utilization/minimization of the effluents for providing a cleaner environment.

Deep-sea ecosystems (DSE) undergo changes which result from natural variability and from human activities, with frequent feedbacks between these two dimensions. Given the seriousness and costs of future deep-sea mining (DSM), a substantial human intervention into the natural environment of the deep-sea, this intervention should be successful (providing the benefits intended), sustainable (providing the benefits in a long term) and responsible (causing the least possible disruption of the deep-sea environment and its communities). The success, sustainability and responsibility of DSM require knowledge of conditions under which the intervention will be carried out as well as the ability to predict the severity of mining effects. The present knowledge on the status and natural variability of ecosystems to be impacted by future mining operations, particularly polymetallic nodule fields on abyssal plains and polymetallic sulphides in hydrothermal vent fields on mid-ocean ridges, is severely limited, as is knowledge on possible consequences of the impacts caused by DSM and rates of recovery from it. We present a brief overview of time-series studies carried out to date in the parts of DSE targeted for future mining operations and discuss the two major dimensions of DSE changes, natural and anthropogenic. We conclude by reiterating the need for intensified, high-resolution observation system(s) of DSE and the necessity of having appropriately resolved time-series of data.

The International Seabed Authority (ISA) is developing a regulation for seabed mining beyond areas of national jurisdiction. On the other hand, there are calls against seabed mining due to concerns about various environmental impacts. One of the key causes for environmental impact is the plume that would be generated by the operation of the mining collector. The potential impact of plume was recognized four decades ago, and about 30 years have passed since four impact assessment experiments were conducted, followed by two long-term monitoring studies. Considering the knowledge accumulated on monitoring the environmental conditions over 25 years, the authors have summarized the findings so far and converted them into a scenario that shows the causal relationship that would lead to the impact of seabed mining.

Adaptive management is widely referenced as a way to manage uncertainty about environmental impacts of an operation. However, it is often perceived as a ‘trial and error’ approach—rather than a structured process that works from a known state and integrates information, learning and management responses to support flexible decision making. Applied in this latter way adaptive management enables operations to be adjusted on a clear pathway to effective environmental management driven by science, or stopped if unacceptable harm is likely.

The chapter is divided into three core sections: the first describes the main concepts of adaptive management and aspects the approach needs to include to be effective; the second presents ideas of how to make the concepts more operational through a participatory systems modelling approach; and the third covers practical managerial and regulatory experience from mining proposals in New Zealand, and lessons learnt about what contractors need to consider in their management plans to help their uptake. Combining these three components can provide important insights for both contractors and managers in helping design and implement plans for adaptive management in deep-sea environments.

Conducting comprehensive environmental baseline studies is a prerequisite for determining effective environmental management strategies for deep-sea mining. Studies conducted along the Kermadec Volcanic Arc have described biological assemblage structure at multiple spatial scales, connectivity of assemblages at different sites, and functional sensitivity of assemblages to Seafloor Massive Sulphide (SMS) mining. Integrating information from these studies highlights the importance of having a highly connected network of protected seabed areas to help mitigate the impacts of SMS mining activities. Using the Kermadec Volcanic Arc as a case study, the additional knowledge required to conduct a full ecological risk assessment is discussed.

Though metal contents of deep-sea mineral resources are ten times or more than on-land ones, deep-sea mining has not been realized in the last 50 years since their first recognition as the potential source of metals in future. Not only some technical issues but also less economic benefits of deep-sea mining are the reasons for non-realization. Assuming metal contents, distribution characteristics, metal prices, and mining methods, some fundamental economic analyses of deep-sea mining have been conducted by the author for all the four types of deep-sea minerals, viz. polymetallic nodules, cobalt-rich ferromanganese crusts, seafloor massive sulfides and rare-earth element-rich mud. These results are discussed in this article. How to improve the economies to realize deep-sea mining by applying new technical approaches is proposed. The approaches include mechanical lifting, ore selection on the seafloor, self-standing riser, combined excavation, pulp-lifting, and reuse of wastes.

The transition toward more environmentally friendly energy production and e-mobility will increase the global demand for metals and minerals. The ocean floor might contribute to meet this demand. This would require that the mineral resources are managed well, from both governmental and industry perspectives. Strategic mine planning is an integrated part of such a management process and is here developed for deep-sea mining based on state-of-the-art methodologies developed for onshore mining. Focus is on seafloor massive sulfides (SMS) deposits known to contain anomalous amounts of, for example, copper, zinc, gold, and silver. It is known that the deposits can form cone-shaped ore geometries. This calls for a mining method inspired from onshore open pit mining. Conceptual 3D geometric and qualimetric models of the Loki’s Castle occurrence along the Arctic Mid-Ocean Ridge are developed. Based on these models and the characteristics of a preferred mining system, a 3D economic block model is developed. This model is used in direct block scheduling with varying sets of assumptions to develop the ultimate pit and schedules for a potential extraction.

Uncertainties concerning deep-seabed mining relate to the expected impacts on the abyssal benthic and pelagic environment and its ecosystems but also include geopolitical, economic, societal and cultural uncertainty. The uncertain impacts from mining lead to anxiety and a low societal acceptance for the activity and are not the same for everybody at the same time. Hence, uncertainty is an important element of the risk involved in deep-seabed mining. This chapter describes the different risks involved, develops a methodology for risk assessment for the exploitation of marine mineral resources that takes into consideration the state of knowledge and evolving research on deep-sea ecosystems, and informs on possible environmental threshold values in relation to deep-seabed mining operations.

In view of the possibility of deep seabed mining commencing in the near future, the International Seabed Authority (ISA) is considering a payment regime for polymetallic nodule mining consisting of a 2% ad valorem royalty for the first 4 years of a mine’s commercial production, increasing to 6% for all subsequent years. As the ISA continues to dwell upon the draft regulations, this chapter evaluates, with the aid of a financial model, this proposed royalty only payment regime. The pros of the proposed regime include that it would be easy to administer, limit scope for tax avoidance and (under our central price and cost assumptions) is consistent with encouraging investment. However, the cons are that this royalty only payment regime is regressive (with the ISA’s share of profits decreasing as the miner’s pre-tax profits increase) and is only consistent with maximising ISA revenues under highly specific assumptions regarding metal prices, sponsoring state tax and costs. A payment regime including a royalty, profit share and excess profit share would be more progressive, but would also be more difficult to administer and prone to tax avoidance.

As the prospect of commercial deep seabed mining comes closer to reality, the International Seabed Authority (ISA) has begun to turn its attention to the question of how to achieve equitable sharing of the benefits from such mining as mandated by the UN Convention on the Law of the Sea. One approach to equitable distribution is to develop a methodology for distribution of net financial benefits based on agreed rules or formulae. Under this scenario, ISA would collect the net financial benefits and transfer the monetary proceeds to a pool of qualified beneficiaries. However, there are inherent weaknesses to this approach. We propose, in line with similar suggestions by the Finance Committee of ISA, that an alternative form of distribution could be a Seabed Sustainability Fund, similar to a sovereign wealth fund, administered by ISA. Such a fund would support and enhance knowledge about the deep-sea for the benefit of all humanity. In line with this, it is envisaged that the Fund could also support other global public goods that benefit all of humanity, such as adaptation or mitigation of climate change, advancing scientific knowledge of the ocean and deep-sea ecosystems, and ensuring biodiversity conservation. These are known to be underprovided and underfunded and could also benefit from funding sourced from and returned to all humanity.

Myriad types of experts participate in developing regulations to manage seabed mining (SBM) in the Area under the auspices of the International Seabed Authority (ISA) pursuant to its mandate under the United Nations Convention on the Law of the Sea, which requires, inter alia, taking “effective measures” to achieve environmentally, socially, economically, and commercially responsible SBM. Interdisciplinary expert contributions to this complex endeavor are essential to designing these measures. Yet continuous, detailed, constructive dialogue between different experts and joint drafting of legally, scientifically, and technologically accurate language to further the “effective measures” objective are often lacking, such that despite the best intentions of everyone concerned, its achievement risks being impeded, and even thwarted, to the detriment of the health of our planet and ourselves. This chapter examines aspects of this “missing link,” drawing on examples from the regulatory process at the ISA. A way forward is proposed for SBM that could also be useful for other activities (marine, terrestrial and atmospheric) requiring continuous, constructive interaction between different groups of experts for their effective regulation and management that is consistent with the legal and institutional framework, adaptable to accommodate improved knowledge and experience, as well as being implementable, enforceable, operationally feasible, and cost-effective.

There are several regulatory frameworks that are already in place from an international context for maritime activities at sea that would apply to deep-sea mining operations and guide the operational implementation of such frameworks. There are also many examples of regulatory frameworks that are implemented by national authorities which are in line with United Nations conventions and agreements that could provide insights for the development and implementation of regulatory and non-regulatory framework for deep-sea mining. This chapter uses analogies drawn from maritime spatial planning and other international regulatory frameworks such as shipping and fisheries to provide insight and lessons learned for the development and implementation of deep-sea mining regulatory and non-regulatory frameworks.

Traditional knowledge, customary marine management approaches and integrated relationships between biodiversity, ecosystems and local communities promote conservation and ensure that marine benefits are reaped in a holistic, sustainable and equitable manner as fostered by contemporary ocean governance. However, the interaction between traditional knowledge, the present scientific approach to marine resource management and specific regulatory frameworks has often been challenging. To a certain extent, the value of community practices and customary rules, which has provided an incentive for regional cooperation and coordination, is acknowledged in several legal systems of the Pacific Island States and a number of regional and international instruments, but this important interconnectivity can certainly be perfected.

Based on recent multidisciplinary research (Tilot et al., Front Mar Sci, 8:637938. 10.3389/fmars.2021.637938, 2021; Tilot et al., Front. Mar. Sci, 2021), this chapter presents a science-based overview of the marine habitats and activities that would be affected by deep Sea mining (DSM) in the Pacific region, along with an analysis of the traditional dimensions and their interconnectivity with the socio-ecological aspects of marine resource management. We then assess whether the applicable regulatory frameworks attach sufficient importance to these traditional dimensions of seabed resource management and cultural representation in the Pacific region. On basis of this analysis, we identify best practices and formulate recommendations with regard to the current regulatory frameworks and seabed resource management approaches to reconcile competing values of the Pacific communities and to sustain the health of the Global Ocean.

In view of the principle of the common heritage of mankind and the duty to carry out activities in the Area for the benefit of mankind as a whole, the interests and needs of developing states must be taken into account. Diverse mechanisms were devised to make sure that developing states are able to participate in deep-sea mining activities in the Area and receive an equitable share of the benefits, but most of these measures are yet to be implemented and the recent trend of partnerships between private deep-sea mining companies and developing states might jeopardize the original objectives.