[co-authors: Claire Robertson, Eran Sthoeger Esq., Riley Arthur, Gigi Lockhart, Benjamin Crowley]
Key takeaways
- Deep Sea Mining (DSM) involves extracting mineral deposits from the seabed (at depths below 200 metres). The deep seabed covers approximately two-thirds of the total seafloor and is rich in deposits of critical minerals required in battery manufacturing such as manganese, iron, cobalt, nickel, and zinc.
- Proponents of DSM argue for its potential to accelerate the net-zero transition through supplementing the world’s battery mineral supplies with marine mineral resources. On 24 April 2025, the United States White House issued an Executive Order expediting a domestic process to authorise the exploitation of resources in areas beyond its national jurisdiction (international waters) under its domestic Deep Seabed Hard Mineral Resources Act.
- Opponents of DSM highlight its potential to cause irreversible disturbance and destruction to habitats and organisms, which may also accelerate global warming. 37 States so far have taken positions against DSM in international waters, some calling for a moratorium, others a precautionary pause, and one a ban.
- While small-scale exploratory devices have been deployed to test machinery for DSM, no commercial mining has yet been undertaken.
Introduction
With news of renewed interest emerging in recent weeks following the United States White House’s Executive Order (Unleashing America's Offshore Critical Minerals and Resources), deep sea mining (DSM) is the subject of both excitement and controversy. Its proponents argue that DSM may be the key to unlocking billions of tonnes of critical battery minerals. Its opponents argue that DSM will cause irreversible damage to the environment. What is clear is that the world – and the International Seabed Authority (ISA) – must strike a balance between protecting unique and ecologically important species in the deep sea and meeting the mineral demand necessary for the transition to net-zero.
This article, Part One in our three-part series, uncovers the basics of DSM – what is it, where the potential mineral deposits are located, who are the key DSM players, the state of play of current DSM technology, and the science for and against DSM.
In Part Two, we will outline the regulatory and legal framework applicable to DSM, with Part Three exploring the geo-politics, the wider international law issues at play and the landscape of international and domestic disputes likely to arise in relation to DSM.
The treasures of the deep sea
The deep seabed covers approximately two-thirds of the total seafloor and is rich in deposits of critical minerals required in battery manufacturing such as manganese, iron, cobalt, nickel, and zinc. These minerals are used in rechargeable batteries that are needed for renewable energy storage, such as for electric vehicle batteries. These mineral deposits come in three forms: polymetallic nodules, polymetallic sulphides, and cobalt-rich ferromanganese crusts. DSM involves extracting these mineral deposits from the seabed at depths below 200 metres.
Figure 1: Types of mineral deposits
Of significant interest to DSM proponents and opponents alike is the Clarion-Clipperton Zone (CCZ), which spans 4.5 million square kilometres in the Pacific Ocean. A conservative estimate is that 21.1 billion dry tonnes of polymetallic nodules exist in the CCZ manganese nodule field, the largest in area and tonnage of the known global nodule fields.1 Based on that estimate, the tonnages of many critical metals in the CCZ nodules are greater than those found in global terrestrial reserves. About 7.5 billion dry tonnes of cobalt-rich ferromanganese crusts are estimated to occur in the Prime Crust Zone, the area with the highest tonnage of critical-metal-rich crust deposits. So far, 19 of the 31 exploration contracts the ISA has issued are for the exploration for polymetallic nodules in the CCZ.
Importantly, much of the CCZ sits in international waters, beyond national jurisdictions. The United Nations Convention on the Law of the Sea (UNCLOS) refers to the seabed, ocean floor, and subsoil beyond limits of national jurisdiction as “the Area”.
Figure 2: Maritime zones according to UNCLOS
A State’s Exclusive Economic Zone (EEZ) extends from the baseline of its territorial sea out to 200 nautical miles from its coast. In that EEZ, a State has rights to explore, exploit, conserve, and manage the natural resources of the waters and of the seabed. As such, a State has the means to permit and regulate DSM within its EEZ without the ISA’s approval, but in line with its obligations to protect and preserve the marine environment.2 The Area, in contrast, is subject to the ISA’s administration. UNCLOS provides that the Area must be protected from harmful effects and any benefits derived from it must be equitably shared among all State Parties.
States such as Norway and the Cook Islands moved swiftly towards DSM in their own EEZs. In January 2024, Norway became the first State to announce the opening of an area of 281,000 square kilometres in its EEZ to commercial DSM exploration.3 However, in November 2024, Norway paused DSM exploration in its EEZ, after it was blocked by the country’s Socialist Left Party. Norway's Prime Minister, Jonas Gahr Stoer, described the pause as “postponement” and said preparatory work on regulations and environmental impact would continue.4
Most recently, talks between China and the Cook Islands regarding research efforts have accelerated.5 Korea, China, and India have all also sponsored, or contracted exploration contracts through the ISA in the CCZ.6 In the private sphere, industrial metals start-up The Metals Company (TMC) leads the charge on DSM. TMC has been granted three exploration contracts through its subsidiaries in the CCZ, sponsored by Nauru, Kiribati, and Tonga. Other private players include Cobalt Seabed Resources and Moana Minerals (who both hold licences in the Cook Islands EEZ), and Global Sea Mineral Resources (GSR) (who hold leases issued by the ISA in the CCZ).
The treasure hunt – technology and proposed process
The technology to be used in DSM is largely untested and the expected processes for mining and processing are in the experimentation phase. There will, however, be a difference in process between the types of deposits.
Nodules
The expected process for DSM of nodules is to transport tractor-sized machines down to the seabed, which would then crawl along the bottom, collecting the nodules and sending them back to the surface via long tubes as they go (almost like “vacuuming” the sea floor). How these machines would collect the nodules is one of the issues still being researched, although most likely the machines would “hoover” the nodules up from the seabed. Given the risks of disturbing and collecting sediment, and neighbouring life forms, alternative methods such as using a special rake to sieve the nodules out are also being explored.
There have been instances of technological failures of nodule-retrieving prototypes so far. While it is difficult to obtain reliable public data on all technology and equipment failures, the most recent known example occurred in April 2021, when a 25-tonne un-crewed prototype nodule mining device became detached from the cable linking it to a ship at the surface during a month-long trial program by GSR. The device became stranded on the seabed but was later reconnected and retrieved.
Crust and sulphides
Polymetallic sulphides can be mined around hydrothermal vents on the ocean floor. The specific process for mining crust and sulphides is, to date, unconfirmed and under-developed, though likely to follow a very similar form to current terrestrial mining.
Crust mining is technologically more difficult than nodule mining. Unlike nodules, which sit on a sediment substrate, crusts are attached to substrate rock, meaning they cannot simply be picked up from the seafloor like nodules. The crust must be separated from the substrate rock before they can be collected. It is anticipated that crust mining operations may include fragmentation, crushing, lifting, pick-up, and separation.7 A general method of crust recovery might consist of a bottom-crawling vehicle attached to a surface ship by means of a hydraulic pipe lift system and electrical cord. The vehicle might use articulated cutters that would allow crusts to be fragmented while minimising the amount of substrate rock collected. The technology to be used in this process is unconfirmed and there have been no field tests of equipment capable of mining cobalt-rich ferromanganese crusts.
The unknown: Evidence against DSM
While small-scale exploratory devices have been deployed to test machinery, no commercial mining has yet been undertaken. As such, there is no clarity on the actual impact DSM may have on the marine environment and whether those impacts will be irreversible. In this instance, the general approach is to adopt the precautionary principle.8 There are those who suggest that DSM will likely cause long-term environmental, economic, and social harms.9 However, the competing argument is that DSM will be a more economically and environmentally responsible alternative to ongoing reliance on terrestrial mining operations for sourcing the battery minerals necessary for the transition to net-zero.10
In a joint publication of Environment America, U.S. PIRG Education Fund, and Frontier Group, ‘We don’t need deep-sea mining’, the authors suggests that DSM is not necessary to meet the global critical minerals demand, analyse the expected environmental impacts, and argue that many of the resources needed for the net-zero transition would already be accessible if we were to utilise a circular economy.11 Ultimately, the publication recommends a moratorium on DSM in the Area.
Further, it is argued that DSM will be highly energy intensive and is likely to produce a high level of greenhouse gas (GHG) emissions, depending on the mining and transport procedure undertaken. However, it is hard to gauge the actual emissions impact without any exploitation activities being commenced to date. There has been very little scientific attention on the potential terrestrial impacts of DSM, including GHG emissions. Scientific studies, investigating the hypothesis that metal production from manganese nodules is less GHG emission-intensive compared to conventional sources, are scarce. The proposed metallurgical processing of nodules is currently similar to that of land ores. Consequently, the severity of climate impact is less dependent on whether ores come from the deep sea or land and is more dependent on the properties of processing: mainly the sources of fuel and electricity used, process efficiency, and processing technique.12
Alongside the minerals 200 to 6,500 metres below the surface, is an estimated 8,000+ undiscovered marine species (including the so-called “gummy squirrel”, a species of sea cucumber discovered in 2018 and gaining instantaneous fame when John Oliver covered DSM in "Last Week Tonight"). Exploration to date suggests that only 0.01 percent of the total area of the CCZ has been sampled by scientists, that 85 percent of the global seabed remains unmapped, and that 90 percent of species discovered are new to science. A recent publication in the Science Advances Journal noted that “sixty-five percent of all in situ visual seafloor observations [from the authors’ dataset, being the “largest deep submergence dataset yet compiled”] were within 200 nm of only three countries: the United States, Japan, and New Zealand [and that] ninety-seven percent of all dives [the authors] compiled have been conducted by just five countries: the United States, Japan, New Zealand, France, and Germany”.13 The authors therefore considered that “the small and biased sample is problematic when attempting to characterize, understand, and manage a global ocean”.14
Even decades after experimental dredging disturbed a site, scientific monitoring confirms that very few ecosystems recover. As such, it is argued that DSM threatens the existence of thousands of species on the sea floor. Some ecological and biodiversity concerns include:
- the direct loss of unique and ecologically important species and populations as a result of the degradation, destruction, or elimination of seafloor habitat, many before they have been discovered and understood;
- the production of large, persistent sediment plumes that would affect seafloor and midwater species and ecosystems well beyond the actual mining sites;
- the interruption of important ecological processes connecting midwater and benthic ecosystems;
- the resuspension and release of sediment, metals, and toxins into the water column, both from mining the seafloor and the discharge of mining wastewater from ships, detrimental to marine life including the potential for contamination of commercially important species of food fish such as tunas;
- noise pollution arising from industrial machine activity on the ocean floor and the transport of ore slurries in pipes to the sea surface, that could cause physiological and behavioural stress to marine mammals and other marine species;
- light pollution from mining activities introducing bright lights into an environment that, but for the biochemical emission of light from living organisms such as glow-worms and deep sea fish, is otherwise constantly dark. This could have significant impacts on species that have adapted to these dark conditions which may be blinded by the introduction of lights from deep sea mining operations; and
- uncertain impacts on carbon sequestration dynamics and deep-ocean carbon storage.
As recently as late June 2025, a new study in the Frontiers in Marine Science Journal also noted that areas targeted for Deep Sea Mining by TMC in the CCZ, contained the presence of one sperm whale (Physeter macrocephalus) which is listed as vulnerable on the International Union for Conservation of Nature's Red List of Threatened Species.15
The opportunity: Evidence for DSM
There is sufficient evidence that DSM will irreversibly disturb, to some extent, the environment and harm life at the bottom of the ocean. However, proponents of DSM note that DSM could be the best – and possibly only – way to meet the growing demand for minerals needed in the transition to renewable energy.16 The deep seabed is believed to harbour quantities of critical minerals that could significantly reduce the world’s dependency on terrestrial mining. Amongst its proponents, DSM is hailed as the “solution” for sustainable development, particularly where some DSM proponents, such as TMC, have indicated that potential damage could be minimised and localised and not spread to wider ecosystems.
Proponents also suggest that ocean mining will be less detrimental than current land-based mining practices, where these activities can harm the environment and local communities through deforestation, air pollution, water contamination, and threats to biodiversity.17 While still mostly untested, DSM operations, when conducted responsibly, may produce fewer GHG emissions and result in less habitat disruption. Fuel consumption, emissions, and air pollution could potentially be reduced in DSM operations as compared to similarly yielding terrestrial mines. It is argued that expansion of land-based mining operations would cause further environmental havoc, and that it is necessary to transition to the sea floor.
One significant concern in relation to DSM is carbon sequestration.18 However, some studies suggest that carbon sequestration from DSM will be less than equivalent terrestrial mining as the global seabed surface potentially contains up to 15 times less carbon than all vegetation and soil on land.19 Because seafloor carbon density is low, and carbon has no known pathway for reaching the atmosphere other than the ocean’s thermohaline circulation or the earth’s geological cycle (tens or hundreds of millions of years), nodule collection is not expected to release significant amounts of carbon sequestered in seabed sediments.
Recently, The Metals Company Australia Pty Ltd commissioned a science consortium project, led by the CSIRO.20 The project developed the first environmental management and monitoring frameworks to protect deep sea ecosystems. The project reports cover an ecosystem-based management framework, explore the impacts of DSM on seafloor species groups and metal bioaccumulation from DSM activities.
Where does DSM go from here?
While the evidence is not yet settled, what it does confirm is that there is a high likelihood of a huge quantity of critical minerals on the seabed floor. Considering the finite amount of critical minerals available terrestrially, and the integral part batteries play in the net-zero transition, DSM may well prove necessary to make it physically and economically feasible to reduce reliance on fossil fuels. That said, as battery technologies continue to evolve, it is possible that deep sea mineral deposits will lose their attraction with alternative technologies not reliant on such minerals becoming more common.
In Part Two of our three-part series, we analyse the regulatory and legal frameworks applicable to DSM.
1 Eleonore Lèbre et al, 'Mining on land or in the deep sea? Overlooked considerations of a reshuffling in the supply source mix' (8 February 2023).
2 See Part XII of UNCLOS.
3 Rod Janssen, 'In January Norway became the first nation to open its continental shelf to commercial deep-sea mineral exploration' (9 February 2024).
4 Maia Davies, 'Norway suspends controversial deep-sea mining plan' (BBC News, 2 December 2024).
5 'Cook Islands dicusses deep-sea mining research with China' (18 February 2025).
6 International Seabed Authority, 'Exploration Contracts' (retrieved 7 July 2025).
7 Liu et al. 'Deep-sea rock mechanics and mining technology: State of the art and perspectives' (9 September 2023).
8 Daniele La Porta, 'The Precautionary Principle Applied to Deep Sea Mining' (August 2021).
9 See generally Rahul Sharma (ed) ‘Environmental Issues of Deep-Sea Mining’ Springer (2019); see further, statement of 827 marine science & policy experts, ‘Deep-Sea Mining Science Statement’; Travis Washburn et al. ‘Ecological risk assessment for deep-sea mining’ (2019) Ocean and Coastal Management 176.
10 Eleonore Lèbre et al. ‘Mining on land or in the deep sea? Overlooked considerations of a reshuffling in the supply source mix’ (2023) Resources, Conservation and Recycling.
11 Lamp et al. 'We Don't Need Deep Sea Mining' (18 June 2024).
12 Daina Paulikas et al. ‘Life cycle climate change impacts of producing battery metals from land ores versus deep-sea polymetallic nodules’ (2020) Journal of Cleaner Production 275.
13 Katherine Bell et al. 'How little we’ve seen: A visual coverage estimate of the deep seafloor' (2025) 11(19) Science Advances.
14 Katherine Bell et al. 'How little we’ve seen: A visual coverage estimate of the deep seafloor' (2025) 11(19) Science Advances.
15 Kristen F Young et al. 'Threatened cetaceans in a potential deep seabed mining region, Clarion Clipperton Zone, Eastern Pacific, August 2023' (2025) 12 Frontiers in Marine Science.
16 Ryan Murdock, 'Deep Sea Mining and the Green Transition' (16 October 2023).
17 Cross Conrad et al. 'Weighting the Environmental Impacts of Deep-Sea Mining' (23 November 2024).
18 'Deep-Sea Mining: A Hidden Threat to Ocean Ecosystems in 2025' (9 April 2025).
19 Paulikas et al. 'Life cycle climate change impacts of producing battery metals from land ores versus deep-sea polymetallic nodules' (28 August 2020).
20 CSIRO, 'Scientists set global benchmark for environmental oversight of potential deep-sea mining' (3 July 2025).
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