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about marine minerals

This page intends to answer the questions most people have, clarify some misconceptions and present the facts about marine minerals.

Find below the questions, issues or concerns we have heard most about marine minerals exploration since IMMS was created. We want to keep adding to our list and making this a useful resource to everyone, so please contact us if you have a different question or issue that was not addressed here. 

1. What is Deep-seabed Mineral Exploitation or Deep-seabed Mining (DSM)?

Deep-seabed mining (DSM) is the term applied to processes and technologies designed to collect metal-rich resources from the deep seafloor. There are three types of deep seabed mineral resources that are of interest to mining companies: seafloor massive sulphides, cobalt-rich ferromanganese crusts, and polymetallic nodules. Extracting sulphides and crusts entails cutting into the seabed surface. By contrast, polymetallic nodules are rock-like accretions that lie unattached on the surface of the ocean floor and can be collected without cutting or drilling. Most interest and investment in DSM is focused on polymetallic nodules. They were discovered almost 150 years ago during the famous HMS Challenger expedition (1872 – 1876), the voyage credited with launching modern oceanography. There are trillions of these nodules, roughly the size of potatoes, lying at a water depth of 4,000 to 6,000 metres in the Clarion Clipperton Zone (CCZ), a six million square kilometre region of the Pacific Ocean’s seafloor between Mexico and Hawaii. Since the early 1970s, there has been growing interest in collecting these nodules due the high-grade and multiple metals they contain – metals like nickel, cobalt, manganese, and copper. DSM is an industry in the exploration, research and development phase. There is no commercial activity (i.e. mining) at all at present.

2. What is driving the demand for the metals found in polymetallic nodules underwater?

The metals found in polymetallic nodules are critical for clean energy technologies such as wind turbines, solar panels, electric vehicle batteries and other energy storage devices. The World Bank[1] estimates that more than three billion tons of these metals will be needed to deploy the wind, solar and energy storage technologies required to keep climate change to below +2°C. As an example of the metal intensity associated with green technologies: electric vehicles use at least four times the amount of metals found in petrol and diesel cars. A single electric vehicle with a 75 KWh battery needs 56 kg of nickel, 12 kg of manganese, 7 kg of cobalt, and 85 kg of copper for electric wiring. But this is just one part of the metal demand story. As with clean energy technologies, urban infrastructure is metal intensive. By 2064 the number of people living in resource-hungry urban locations is forecast to increase by 1.93 billion[2]. Remarkably, to accommodate this swelling urban population, the equivalent of 229 New York Cities will need to be built in the next 40 years, putting huge pressure on already strained resources. [1] Minerals for Climate Action: The Mineral Intensity of the Clean Energy Transition, World Bank, 2020 [2] Fertility, mortality, migration, and population scenarios for 195 countries and territories from 2017 to 2100: a forecasting analysis for the Global Burden of Disease Study, Stein et al, 2020

3. Where are we getting these metals from nowadays?

Today all of the world’s primary metals are sourced from land-based mines. About 70 per cent of the world’s cobalt comes from the Democratic Republic of Congo (DRC), with the balance coming from Russia, Australia, Cuba, Madagascar, Papua New Guinea and Canada. Nickel is primarily mined in Indonesia, Philippines, Russia, and New Caledonia. Because the ore grade of land-based deposits is declining, new sources of metal supplies are being explored, often in remote and ecologically sensitive regions, including rainforests. While many mining companies act responsibly there is no escaping the fact that land-based mining is carbon intensive, often results in deforestation, creates mountains of waste – some of it toxic – and can lead to the displacement of peoples. Nickel, copper, manganese and cobalt never appear together in terrestrial deposits; two to three separate land-based mines are needed to extract them. The multi-metal nature of polymetallic nodules means that a deep seabed mining area is, in effect, two or three land-based mines in one, which means there is the potential to reduce waste and CO2 emissions per tonne of metal mined and minimise a number of other negative environmental and social effects. The world is certainly not running out of land-based metal. There are enough resources to meet demand. The problem is that mining these resources comes with a heavy environmental burden, and as exploration takes miners into ever more remote and biodiverse areas, the scale of that burden will only grow. DSM may represent a better way of meeting future metal demand. It certainly won’t replace land-based mining entirely, but it may contribute to a less carbon intensive way of providing the metals we all need, and it may have fewer ecosystem effects overall. Continued research will provide the evidence that all stakeholders need to draw rational conclusions about how best to proceed.

4. Who is proposing to retrieve these nodules from the seabed in International waters?

No one yet. There are a number of marine research and engineering entities currently engaged in DSM exploration. Each is sponsored by a member State of the International Seabed Authority (ISA). They operate under a contract with the ISA that allows for exploration only, not commercial activity (i.e. mining). Sponsoring States include but are not limited to China, Japan, Russia, France, UK, Korea, Germany, Poland, Cook Islands, Nauru and Belgium. It is unlikely that any commercial activity will begin before 2027. That’s because, even for the most advanced ISA contractors, years of further environmental studies and testing lie ahead.

5. Who regulates mineral exploration in International waters?

Never before has so much thought gone into regulating an industry before it even exists. No State or entity can commercially explore the seabed or collect nodules except under contract with the International Seabed Authority (ISA). The ISA is mandated through the UN Convention on the Law of the Sea (UNCLOS) to organize, regulate and control all mineral-related activities in the international seabed area and for the benefit of humankind as a whole. To date, the ISA has awarded 18 exploration contracts in the CCZ. The contractors who hold these 15-year licences represent nations including China, Japan, Russia, France, UK, Korea, Germany, Poland, Cook Islands, Nauru and Belgium. All exploration contract holders are undertaking geological and environmental studies, as part of their contractual obligations. The ISA is in the process of developing regulations for commercial activity and any contractors wishing to undertake mining operations in the international deep seabed area will need to abide by these strict regulations. The regulations incorporate specific provisions to ensure the effective protection of the marine environment and conservation of marine biodiversity, human health and safety, and a system of payments which aims to ensure the equitable sharing of financial and other economic benefits derived from seabed minerals. The regulations must be agreed and adopted by the ISA Council and approved by the ISA Assembly, comprised of 167 Member States and the European Union.

6. How much of the seabed contains these minerals that the world needs?

The majority of interest and investment in DSM is focused on polymetallic nodules in the Clarion Clipperton Zone (CCZ) of the Pacific Ocean. Nodules found in the CCZ contain 1.2 times more manganese, 1.8 times more nickel and 3.4 times more cobalt than all known land-based reserves combined.[1] The CCZ represents about 1.6% of the world’s oceans. Of this, about 30% has been set aside as protected areas or APEIs (Areas of Particular Environmental Interest). Of the remainder, about 21% has been reserved for DSM exploration but only about 30-50% of that might feasibly one day be mined, in part because each contractor must identify ‘set-aside’ areas that have similar habitats and stable biota to the mining area. This means if all CCZ contract areas were to be developed, this would amount to an area of approximately 0.1 to 0.2% of the world’s seafloor. By comparison, every year deep sea trawling fisheries impact 4.9 million km2, which amounts to approximately 1.3% of the global ocean.[2] [1] Deep-ocean polymetallic nodules as a resource for critical materials, Hein et al, 2020 [2] Protecting the global ocean for biodiversity, food and climate, Sala et al, 2021.

7. What is a moratorium and why some people are calling for it?

The research that moratorium campaigners are calling for is already required by the International Seabed Authority (ISA). All research data and results are submitted annually to the ISA and will be incorporated into an Environmental Impact Assessment (EIA) which will culminate in an Environmental Impact Statement (EIS). The EIS needs to be submitted as part of an application for a mining contract along with an Environmental Management and Monitoring Plan, Closure Plan and a number of other documents. It is important to recognise that a moratorium would have the opposite of the claimed effect. Far from creating time and space for more research to be conducted, it would act as a disincentive to invest in deep sea exploration. If the science shows the deep seabed has no advantages over the alternatives – which is to rely solely on opening up new mines on land to access new sources of metal – there will be no DSM industry. Protesting against DSM research is like protesting against the clinical trial of a vaccine until the outcome of that trial is known. It is illogical, anti-science and irresponsible.

8. Is it possible that by extracting these minerals from the deep-ocean we may damage local seafloor ecosystems?

There is no way of extracting metals without some environmental effects. The fundamental question surrounding DSM is this: can it be counted among the more responsible ways of sourcing the metals the planet needs? More specifically, how does the collection and processing of polymetallic nodules compare with future land-based mining with respect to carbon emissions and other environmental effects such as freshwater eutrophication and acidification? And how do the two compare from the perspective of ecosystem health and function? There are good reasons to believe that obtaining metals from the seabed will compare well because the grades and multi-metal nature of nodules means that one mining area on the seabed produces the same volume of metals as two or three mines on land. With DSM there is no deforestation, no need to relocate people and no mountains of often toxic waste. The recent Patania II trial was part of a multi-year research program involving numerous scientists from some of the world’s leading research institutions and universities. A key aspect of this research is to be able to predict, validate and monitor environmental effects. Learnings will inform future engineering design, mine planning and environmental management with the aim of reducing impacts to the fullest extent possible. All research data, results and learnings will be incorporated into an Environmental Impact Assessment (EIA) which will culminate in an Environmental Impact Statement (EIS). The EIS needs to be submitted to the International Seabed Authority as part of an application for a mining contract along with an Environmental Management and Monitoring Plan. This plan will be designed to ensure the conservation of ecosystems on the deep seafloor and will entail responsible environmental management strategies such as establishing representative set-aside areas and possibly remediation measures such as replacing nodules with alternative habitats (note remediation research is ongoing).

9. Some NGOs like Greenpeace do not approve of deep-sea minerals exploration. Do they have a valid point?

While Greenpeace and other NGOs may not see a role for deep seabed mining in the transition to a sustainable future, it is premature to discard it as an option for delivering the metals the planet needs to realize a circular economy and a clean energy future. At this point, DSM is in a research phase. Contractors are undertaking detailed multi-year environmental baseline studies and completing an environmental impact assessment. The expedition to which Greenpeace objected is part of this scientific process and the field trial was designed to better understand environmental effects of collecting minerals from the seafloor so that informed decisions can be made, based on the best scientific information possible.

10. What kind of environmental and impact research will potential marine mineral exploration companies be required to do?

With regard to DSM, the research required during the exploration phase takes years to complete and includes an environmental impact assessment, which will culminate in an Environmental Impact Statement (EIS). The EIS, along with an Environmental Management and Monitoring Plan and a Closure Plan, must be submitted to the International Seabed Authority (ISA) as a part of the application for a mining contract, which will then be evaluated by the ISA, comprising representatives from 167 Member States plus the EU. The International Seabed Authority (ISA) is mandated through the UN Convention on the Law of the Sea (UNCLOS) to organize, regulate and control all mineral-related activities in the international seabed area and for the benefit of humankind as a whole. In so doing, ISA has the duty to ensure the effective protection of the marine environment from harmful effects that may arise from deep-seabed mineral related activities. It is important to remember that what States are sponsoring at this stage is exploration, not commercial activity. Through exploration and research, we are able to understand the effects of DSM on the marine environment and establish responsible environmental management strategies.

11. Why can't recycling provide all the metals we need?

We should all be working towards a future where most of the metals in circulation come from recycled sources, but all credible studies conclude that enormous quantities of primary resource will be required first. Current land-based sources will make a contribution, but they can’t do it all. We will need new sources of metal. Expanding recycling will also play a part but can only make a modest contribution. That’s because of long in-use lifetimes (an offshore wind turbine is expected to last more than 30 years for example) and also because of low efficiencies in collecting and processing end of life materials. In one study[1], end-of life batteries are expected to contribute 7% to the overall demand for raw materials for battery production in 2030, but even this will require recycling capacities to be increased by a factor of more than 25 compared with today. Beyond recycling, strategies such as material substitution, product re-use and product re-design may be able to place a brake on society’s thirst for metals, and future technological advances may also help to dampen demand. However, the scale and pace of forecast demand is so high that significant new sources of metal will still be needed in the coming decades, and we have some important choices to make about where we obtain these metals from. [1] GBA/WEF: A Vision for a Sustainable Battery Value Chain in 2030

12. Who will benefit if deep-sea marine minerals exploration is approved?

Metal is one of our biggest allies in the battle against climate change, but it comes at a cost: there is no way of extracting metal without some environmental effects. If the deep seabed can help us meet future metal demand in a more responsible way than alternatives, then we all stand to benefit. In addition, under the UN Convention of the Law of the Sea (UNCLOS), the economic advantages of DSM are to be shared for the benefit of humankind as a whole, in the form of royalty payments, with particular emphasis on the developing countries. Entities that invest in DSM exploration and research will, of course, benefit from commercial activity but if DSM does become an established industry it will only do so because years of scientific research have demonstrated that it will deliver the metals needed for clean energy transition and sustainable development in a responsible way.

13. What is the biggest threat to the oceans and won’t collecting nodules make things worse?

The biggest threat to the oceans is climate change. The top priority for the entire planet—including the oceans—should be achieving net-zero emissions. Staying dependent on fossil fuels will continue to contribute to a host of environmental and climate issues—ocean acidification, oil spills, toxic byproducts, resource wars, and child labor among them. Shifting away from carbon-based energy requires a huge amount of energy storage, in the form of batteries, for both vehicles and the grid. The bulk of those batteries will be made of yet-to-be-sourced metals that must come from somewhere. High-grade and easy-to-access metals from land-based mining operations have already been extracted. This diminishing return of land metals means that the metals remaining are of a low grade: A huge amount of useless material in these ores becomes toxic pollution after mining, and ores containing nickel in particular are largely found beneath equatorial rainforests. These forests sequester carbon for the entire planet, land and oceans combined. Peer-reviewed research by Paulikas et al, 2020 shows that sourcing the metals needed for the transition to clean energy from high-grade polymetallic nodules can reduce the associated climate impacts by 90% compared to land-based ores. Learn more about the impacts of terrestrial mining alongside those of collecting polymetallic nodules here.

14. Can some deep-sea minerals be extracted more safely than others?

There are three distinct types of deep-sea resources, each of which are found in differing ecosystems and vary in their impacts. The differences are important to consider when looking at our planetary footprint. Cobalt crusts precipitate on the flanks of submarine volcanoes (or “seamounts”) as metallic layers that form an integral part of the seafloor and require cutting hard rock to separate the ore from the substrate. At depths of between 800–2,500 meters, the local ecosystem enjoys an abundant food supply, thanks to the upwelling of nutrient-rich water, which enables a proliferation of life—including large predators such as tuna and sharks—between 10 to 100 times greater than is found on the abyssal plain. Seafloor massive sulfides are tall, chimney-like structures that form around hydrothermal vents spewing forth metal-enriched waters from the seafloor. Similar to cobalt crusts, these formations are an integral part of the seafloor and require hard-rock cutting to separate the ore from the substrate. At depths of between 1,000–4,000 meters, bacteria, which exploit chemical compounds from the vents, supply this ecosystem with an abundance of food, supporting biomass levels 100 times greater than those on the abyssal plain. By contrast, polymetallic nodules lie unattached atop the abyssal seafloor and can be collected using water jets directed at the nodules in parallel with the seafloor—without any digging or drilling. At depths of between 4,000–6,000 meters, the abyssal CCZ is a stable environment with little food, and one of the least productive areas of the ocean with one of the lowest biomass levels of any planetary ecosystem.

15. Won’t deep-sea mining impact climate change by disrupting marine carbon sinks?

Collector vehicles operating in the abyssal zone at 4–6 kilometer depths will likely disrupt the top 5 centimeters of sediment, separate it from nodules inside the machine, and redeposit it at the seafloor. Recent studies and our own modeling conducted by the Danish Institute of Hydrology show that a majority of this sediment will resettle within days and hundreds of meters of origin. No known mechanism exists for carbon-bearing sediment to travel up the water column and reach the atmosphere. There are also no known methane hydrates in the Pacific Ocean’s Clarion Clipperton Zone [1], where we’re exploring with oversight and regulation by the International Seabed Authority. At the abyssal depths found in the CCZ, both inorganic carbon and methane are soluble in water, and neither forms bubbles that could rise to the surface. Contrary to this claim, peer-reviewed research comparing the life-cycle climate change impacts of supplying 1 billion EVs with nickel, copper, cobalt, and manganese shows that using nodules to produce these metals, rather than getting them from land-based resources, would reduce the associated climate change impacts by 90%.[2] [1] Where are gas hydrates found? (n.d.). [2] Paulikas et al. (2020). Life cycle climate change impacts of producing battery metals from land ores versus deep-sea polymetallic nodules. Journal of Cleaner Production, 275. (

16. Environmental and social impacts of land-based mining are well understood and can be addressed because operations on land are accessible. Will the impacts of deep-sea mining be invisible and less well understood?

While understanding and witnessing the environmental and social damages of land-based metal production is one thing, reducing them is another [1]. The theoretical potential for reducing harm on land is severely constrained: We can’t change the fact that the grades of remaining ores are low and falling, nor can we change the fact that if the rock contains only 0.5% of target metal, the other 99.5% will become a waste stream. We also can’t change the fact that remaining battery metal deposits are located in places with high biodiversity, often on Indigenous land. The life-cycle Environmental, Social, and Corporate Governance (ESG) footprint for land-based production can be improved, but in most cases, it will always be much worse than the life-cycle ESG footprint of nodule-derived metals. This is simply because the starting point for the nodule resource is fundamentally different: rich concentrations of four metals in a single rock; an entirely usable rock mass; a barren and common, desert-like environment with limited life; and no threat to Indigenous land. Additionally, the Clarion Clipperton Zone is physically remote, but will not be “out of sight, out of mind.” [1] Paulikas et al. (2020). Life cycle climate change impacts of producing battery metals from land ores versus deep-sea polymetallic nodules. Journal of Cleaner Production, 275. (

17. Will sourcing metals from polymetallic nodules undermine prices and incentives to scale up recycling?

Given the aggressive scale-up of demand driven by the world’s transition to clean energy, metal shortages are likely to persist for some time as metal producers make the large investments required to scale up supply. As metal supplies grow over time, metal producers will start competing on price and sustainability. At this point we expect that recycled metal will start displacing new metal supply from land-based sources due to its much better sustainability profile—even if it comes with a higher price tag. This scenario is supported by the fact that many jurisdictions around the world are making recycling of electric vehicle batteries a regulatory requirement. If done right, recycled metal is the only truly sustainable source of metal. Metals derived from nodules will likely coexist with recycled metal for a few decades due to their lower production cost and lower ESG footprint, but will gradually be phased out as the world builds up sufficient stocks to enable a fully recycled metals commons.

18. Isn’t the deep sea a pristine environment that should not be touched?

No ecosystem is immune to the impacts of industrial society, including the deepest parts of the ocean. In its upper layers (0–2,000 meters), the ocean continues to warm unabated [1]. It’s likely that this surface warming impacts the deep sea. The ocean is also continuing to acidify as it absorbs more CO2 from the atmosphere [1]. With this in mind, we view it as our primary focus to reduce the CO2 in our atmosphere, thereby reducing ocean warming and CO2 absorption into the oceans. This requires a massive and rapid injection of metals for batteries for electrification. The impacts of supplying this booming metals demand from conventional terrestrial sources will only deepen the degradation of our planet’s oceans and biodiverse ecosystems, including through an increase in atmospheric carbon and, in certain cases, the disposal of mine waste and tailings directly into the deep sea. Polymetallic nodules can provide a cleaner path forward that can curtail these impacts and meet the needs of the clean energy transition at the same time. [1] Bindoff, N.L. et al. (2019). Changing Ocean, Marine Ecosystems, and Dependent Communities. IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. Retrieved from

19. Could nodule collection lead to the extinction of species in the deep sea?

While we cannot promise that no species will go extinct in the deep sea, we know we can do much better than the status quo when it comes to metal production. Mining on land has driven species extinction and biodiversity loss for centuries. Even in countries with stringent environmental regulations, biodiversity-related impact studies typically focus only on keystone species above ground. They do not consider biodiversity comprehensively and ignore the estimated 99% of microbial species and 80% of worm species yet to be studied [1] under the soil. As mining increasingly moves into the most biodiverse ecosystems on the planet, species extinction and biodiversity loss will likely increase. Nickel production in Indonesia is of particular concern and has been described as the mined commodity most susceptible to biodiversity risks. Nodule collection, by contrast, would take place at 4–6 kilometers depth on the abyssal plain of the Clarion Clipperton Zone, where there are several orders of magnitude less life than on land. This is one of the least populated areas on the planet (300–1,500 less biomass than on land [2])— with no plants, no light, high pressure and few sources of food. Seventy percent of its low resident biomass is made up of microbial organisms, with the remaining biomass comprising a small population of deep-sea worms, sponges, and fish. The abyssal plain is the most common environment on the planet, covering more than 60% of the planet’s surface [3], and quite unlike the unique ecosystems that mining on land threatens. On the abyssal plain the risk of species extinction and biodiversity loss can be reduced by setting aside large areas of the abyssal plain for conservation; the ISA has already set aside more area under protection in the CCZ than is currently under exploration. As part of our ongoing Environmental and Social Impact Assessment program, we’re studying species throughout the overlying water column and above the surface to make sure we understand how these ecosystems interact and function. This comprehensive approach goes beyond typical land-based impact studies, and includes understanding microbial populations and worms living in the seafloor mud. This will help us make better decisions about how to further mitigate our impacts, what additional areas to set aside, how to design our collector robots, at which depth to return seawater used to lift nodules from the seafloor, and what indicators to monitor during operations to keep within safe ecological boundaries. We believe that sourcing battery metals from loose-lying polymetallic rocks in the CCZ puts us in a better position to reduce the risk of species extinction than intensifying land-based extraction for these same metals in unique and highly biodiverse terrestrial ecosystems. [1] Guardian News and Media. (2020, December 4). Global soils underpin life but future looks “bleak,” warns UN report. The Guardian. [2] Bar-On, Phillips, & Milo. (2018). The biomass distribution on earth. Proceedings of the National Academy of Sciences of the United States of America. 115(25), 6506-6511. doi:10.1073/ pnas.1711842115. [3] Paulikas et al. (2020, April). Where Should Metals for the Green Transition Come From? Deep Green. Retrieved from

20. Would each nodule operation effectively strip mine vast areas of the seafloor?

Strip mining on land is the removal of vegetation, soil, and rock (also known as “overburden”) above a layer or seam of minerals, followed by the removal of the exposed mineral. During this process, the entire surface ecosystem is removed before excavation is used for softer rocks, and drilling and blasting is used to break up and remove the subsurface hard rock. Collecting polymetallic nodules is quite different. Nodules are loose rocks sitting exposed on top of the seafloor, with 95% of nodule mass contained in the top 5 centimeters of sediment. There is no overburden to remove. As nodule collectors move along the seafloor, they direct jets of seawater across the nodules to lift and collect them inside the machine, using the Coandă effect. While up to 5 centimeters of soft mud under the nodules will travel inside the vehicle, almost all of this will be separated and redeposited back at the seafloor. This process is engineered to minimize impact on the marine environment and involves no strip mining, drilling or blasting of the seafloor [1]. It’s also worth noting that nodule collection is projected to impact 40,000 square kilometers of the abyssal seafloor per year for 30 years. This is less than 1% of the estimated 4,900,000 square kilometers of the seafloor impacted every year by trawling, largely in much shallower and more productive waters [2]. [1] E. Baker, Y. Beaudoin (Eds.), Deep Sea Minerals: manganese Nodules, a physical, biological, environmental, and technical review, Secretariat of the Pacific Community, 1B (2013) [2] Sala, E., Mayorga, J., Bradley, D. et al. (2021). Protecting the global ocean for biodiversity, food and climate. Nature 592, 397–402.

21. Will sediment plumes kicked up by nodule collector vehicles travel thousands of kilometers?

Anti–deep-sea-mining campaigners emphasize the long distances over which the finest sediment particles (less than 5% of suspended mass) from nodule collection could travel before resettling onto the seafloor. This emphasis has led to considerable speculation about extensive and widespread impacts of deep-sea-mining activities. However, these speculations are not grounded in science and there is a growing body of evidence showing that these impacts have been overstated. Nodule collection operations will create two distinct plumes: the disturbance and suspension of seafloor sediments by nodule collector robots (‘seafloor plume’) and the reintroduction of residual sediment and nodule fines into the midwater column as seawater used for nodule transport is discharged from the riser outlet (‘mid-water plume’). Recent in-situ experiments and studies show that the vast majority of seafloor sediment kicked up during operations will settle quickly, mostly within 4 kilometers and within a few days, and dilute rapidly to natural background concentration levels—the most relevant metric for sea-life impact—within 1 kilometer. Furthermore, successful trials of the ‘Patania II’ collector vehicle by contractor Global Sea Mineral Resources (GSR) found that this sediment rarely rose more than 5 meters above the seafloor. These findings are supported by plume modelling for trials of our pilot collector system conducted by the Danish Hydrology Institute (DHI) [link] as part of our ESIA program. Taken collectively, this real-world data and modelling suggests that it is highly unlikely that any direct pathway exists in which suspended carbon-bearing sediment could travel to the surface from depths of at least 4,000 meters, all but eliminating the risk that nodule collection could contribute to greenhouse gas emissions.

22. Will 'tailings' be discharged into the mid-water column and introduce sediment and dissolved metals over potentially large areas?

Although the sediment-seawater mixture that will be returned into the midwater column is often referred to as “tailings,” the two should not be confused. Tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore. Tailings are distinct from “overburden,” which is the waste rock or other material that overlies an ore or mineral body and that is displaced during mining without being processed (i.e., chemically). While our processing flowsheet eliminates tailings by design, other contractors may pursue different pathways, but none are currently proposing to release tailings from nodule processing at sea. Small amounts of residual sediment and abraded nodules found in the seawater used for nodule transport are more analogous to the removal and redeposition of overburden during a terrestrial mining operation. A recent study by researchers at MIT and plume modeling conducted by the Danish Hydrology Institute (DHI) for our ESIA shows that the turbulence of this plume upon re-entry into the water column limits the ability of sediment particles to stick together [1]. Based upon emerging data, a long-term commercial mining operation can be expected to elevate sedimentation rates by as little as 1% to the impacted areas. One outstanding question that our ESIA is currently in the process of addressing is whether increased quantities of sediment falling to the seafloor are likely to be detrimental to deep-sea fauna and habitats, which have evolved in an environment naturally subjected to wide variations in sediment load. Ultimately, limiting the amount of sediment brought up with the nodules to the surface will play a primary role in setting the scale of the impact of midwater plumes. This is why our engineering partners, Allseas, are focused on optimizing our collector and riser system to further reduce our impacts. Nodules are friable, and turbulence will cause some fragmentation during their rise to a collection ship, where screens and centrifuges will retain particles larger than 10 microns, with smaller particles entering the return flow. The increased bioavailability of heavy metals contained in these particles has been a historic cause for concern, however these metals are all present as compounds, which may have less toxicity than in free ion form. New research finds that, for some metal compounds, nodule collection is unlikely to exceed toxicity thresholds. Further research on this topic is being considered as part of our ongoing Environmental and Social Impact Assessment. [1] Muñoz-Royo, C., Peacock, T., Alford, M.H. et al. Extent of impact of deep-sea nodule mining midwater plumes is influenced by sediment loading, turbulence and thresholds. Commun Earth Environ 2, 148 (2021)., K., & Alford, M. (December 7, 2019). PLUMEX – MOD News – blog. MULTISCALE OCEAN DYNAMICS.

23. Is it true that a single nodule collection operation would discharge 50,000 cubic meters of sediment, broken mineral fines, and seawater per day, and could run for 30 years, releasing 500,000,000 cubic meters over its lifetime?

Nodule collection displaces very soft clay that lies beneath each rock. With no overburden, this waste stream differs from terrestrial waste, as it’s composed almost entirely of seawater. The first nodule-collection waste stream is made up of displaced sediment (13.8 kilograms per square meter) redeposited on the seafloor. The second accounts for a small portion (around 8%) of remaining sediment, which enters the riser, is combined there with a mass of nodule fines, and is then returned to below 1,200 meters, at a depth scientifically chosen to have minimal impact. It’s also worth noting that both the mining phase on land and the nodule-collection phase in the deep sea tell only half the story. On land, nickel sulfide, copper ore, and cobalt concentration produce large waste flows. As ore grades decline further, concentration waste will increase significantly and in the next seven years, it is expected that society will produce more processing tailings from copper production alone than have been produced in all of human history. While waste generated from nodule processing is dependent on methodology and flowsheet, high ore grades and nodules’ lack of toxicity enable zero-solid-waste processing. When sourcing metals for 1 billion electric vehicles (EVs), nodules would generate no solid processing waste and no toxic tailings [1]. [1] Paulikas et al. (2020, April). Where Should Metals for the Green Transition Come From? Deep Green. Retrieved from

24. Will deep-sea ecosystems recover from deep-sea mining?

Present, modern technology, nodule collectors are being engineered to only remove most nodule cover around the top 5 centimeters of sediment. Recovery can start naturally and immediately after the collector moves on. Between the 1970s and present, scientists have conducted 11 seafloor disturbance and commercial mining studies. They repeatedly revisited these sites over a 26-year time period to measure each area’s recovery. Review studies of research to date show that mobile and pelagic fauna density and diversity recovers within one year [1] , and that microbial density, diversity, and function (70–80% of the total biomass impacted by nodule operations) are expected to recover within 50 years [2]. New nodules will continue forming on the impacted site, but it will take up to 5 million years to regenerate nodule cover comparable to pre-disturbance state. Recovery of species that need the hard substrate of nodules (less than 10% of the total biomass impacted) is currently not known and depends on habitat connectivity, recruitment, and the extent of remaining nodule coverage. Compare this rate of recovery to the default driving nickel supply growth today: mining nickel laterites in Indonesia [3,4]. The entire overlying rainforest ecosystem is removed (trees, plants, soil, rock, and all animals and microbes living therein). As the rainforest is cleared, the organic carbon it contains is released, and the below-ground microbial and worm populations are impacted. Recovery often only begins when mine operations cease in the area (this can take many years) and requires active restoration efforts and funding by the mine operator or local government. It can take hundreds or thousands of years to regenerate new soil and forests that can support previous levels of biodiversity [5]. Nickel laterites that are removed can reform through continued weathering and wet leaching of unweathered rock, but—like nodules—will take millions of years. [1] Jones, D. O., Kaiser, S., Sweetman, A. K., Smith, C. R., Menot, L., Vink, A.,Clark, M. R. (2017). Biological responses to disturbance from simulated deep-sea polymetallic nodule mining. PLoS ONE, 12(2), e0171750. doi:10.1371/journal.pone.0171750. [2] Vonnahme, T. R., Molari, M., Janssen, F., Wenzhofer, F., Haeckel, M., Titschack, J., & Boetius, A. (2010). Effects of a deep-sea mining experiment on seafloor microbial communities and functions after 26 years. Science Advances, 6(18). doi:10.1126/sciadv.aaz5922. [3] Ghose, M. (2001). Management of topsoil for geo-environmental reclamation of coal mining areas. Environmental Geology, 40, 1405–1410. doi:10.1007/s002540100321. [4] Block, P. R., Gasch, C. K., & Limb, R. F. (2020). Biological integrity of mixed-grass prairie topsoils subjected to long-term stockpiling. Applied Soil Ecology, 103347, doi:10.1016/j.apsoil.2019.08.009. [5] Haynes, R.J. (2014). Nature of the belowground ecosystem and Its development during pedogenesis. Advances in Agronomy, 127: 43–109.

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