In April 2025, Donald Trump Signed a decree authorizing deep-sea mining (Deep Sea Mining) and arousing international outrage over a practice with a vague regulatory framework and uncertain environmental impacts.
Deep sea mining involves extracting mineral deposits from the depths of the ocean. The targeted mineral resources are strategic and necessary for the energy transition : cobalt, copper, nickel and manganese. These metals are contained in polymetallic sulphides (on hydrothermal vents) and cobalt-rich crusts (on seamounts), but especially in polymetallic nodules, pebbles formed by the precipitation of these metals around a core. They are the main interest of deep sea mining today.
Polymetallic nodules are typically found at the surface of the soil of the abyssal plains, between 4000 and 6,000 m deep. They are mainly located on the ocean floor of international waters, beyond Exclusive Economic Zones (EEZ) and national courts. An area of interest for mining is the Zone of Clarion-Clipperton (CCZ) in the Pacific Ocean, in which extraction tests had already been carried out as early as 1979.
Fig. 1: Distribution of mineral resources in the seabed
Source: https://www.wri.org/insights/deep-sea-mining-explained
Deep-sea mineral resources would make it possible to cover the needs for energy transition technologies. According toOUCH, the expected production of copper and lithium by 2035 is likely to be up to 40% less than demand. Approximately 21 Gt (dry) polymetallic nodules would be found in the CCZ, and there are a lot more manganese, cobalt and nickel resources in deep water than on land. Polymetallic nodules contain approximately 30% of manganese, 1.4% of nickel, 1.14% of copper and 0.2% of cobalt; thus, in the CCZ zone alone, we can hope to recover about 2.4 Gt of copper, which would be more than enough to cover the Estimated demand until 2040. However, the economic profitability and relevance of deep sea mining remain debated: the offshore environment creates technical and expensive challenges, and battery technologies are evolving rapidly, in particular thanks to improved battery recycling and the emergence of technologies that do not include cobalt or nickel. Les CAPEX and OPEX of such an undertaking would amount to several billion dollars.
Mineral deposits must in fact be extracted and then transported to the surface to be treated. Extraction is done in several steps :
- Mining vehicles remove mineral deposits from the surface of the seabed, as well as the upper layers of sediment, by vacuum or robotic arms.
- The materials collected are Pipeline lifts to a surface ship.
- On board the ship, the nodules are sorted, washed and stored. Excess residues or sediments are discarded.
- The nodules are transferred onto a transport ship and taken to refineries to extract the metals.
Polymetallic nodule collection and pipeline lifting systems are mature technologies, but the exploitation of polymetallic sulphides and cobalt-rich crusts requires less advanced techniques for fragmenting and drilling hard rocks.
Fig. 2: Principle of extraction of mineral resources
Source: https://www.sciencedirect.com/science/article/pii/S2950154724000060#sec0040
In international waters, it is the International Seabed Authority (AIFM) Who is in charge of manage mineral resource activities and to ensure the protection of the marine environment. The AIFM awards exploration and exploitation contracts to States parties (or to private organizations sponsored by a State Party) to the United Nations Convention on the Law of the Sea (UNCLOS). To date, no operating contract has been issued by lack of finalized regulatory framework.
The United States, having not ratified UNCLOS, is not legally required to go through the AIFM to obtain an operating contract. Thus, while commercial deep-sea mining does not yet exist today, the situation could change following the signing of Trump's executive order. The Metals Company, the first deep sea mining company, announced that it had filed A request for commercial exploitation in the Clipperton area near the NOAA.
Some countries For their part, they are considering mining in their EEZ. Norway has finally suspended the granting of extraction permits for 2024 and 2025 and only allows mineral exploration for now.
From an environmental point of view, landmines cause deforestation, GHG emissions, water pressure and impact local populations, which is what deep sea mining could avoid. However, its environmental impacts are not not yet well identified and studied. This activity could greatly disrupting ecosystems of the seabed through noise and light pollution and sedimentary feathers, as well as limiting the ocean's carbon sink potential. The practice is based on an uncertain regulatory framework and raises numerous environmental questions that are still unresolved.