Some environmental groups have campaigned vigorously to stop polymetallic nodule harvesting, and they have been effective.  They have been loud, they have been organized, they have been well-funded, and they have used many different channels to attack this nascent industry.  They have been successful in delaying the International Seabed Authority (a body within the United Nations that governs ocean activities in international waters) from creating a set of rules that would allow nodule harvesting to happen in international waters and they have signed a number of prominent consumer brands and some countries to their moratorium on seabed mineral extraction.  While their campaigns have garnered the groups a lot of attention, their efforts have also been very damaging to the environment and to some of the most vulnerable members of society.  This section helps to explain how these NGOs and a handful of large consumer brands are actively bringing harm to the planet and to vulnerable people – harm that could easily be avoided.  

We should note that the data, studies, and logic offered here do not extend to the extraction of other mineral formations from the seabed including cobalt crusts, seafloor massive sulfides (extinct hydrothermal vents (smokers)), rare earth muds, methane hydrates, or mineral rich sands.  The specific location of those resources and the methods for their extraction are significantly different from those connected to polymetallic nodule harvesting.  Those resources may be recoverable at some point in the future, but we believe that polymetallic nodules represent the best opportunity for society to harvest critical minerals today while creating net environmental benefits for the planet.

Environmental groups which oppose nodule harvesting have generally avoided using critical thinking to evaluate the practice, preferring instead to take a one-sided approach that puts a premium on emotive appeals over objective thought.  Virtually every critique of nodule harvesting by these anti-harvesting groups fails to compare the practice’s impacts to the impacts of the alternative – terrestrial mining for the same metals (often by Chinese firms who are known to take shortcuts on environmental protection).  The lack of comparative analyses leaves these NGOs without a valid yardstick to measure costs and risks associated with the activity.  Without a yardstick, these groups rely on absolutes to measure costs and risks which renders their analyses nearly meaningless in the context of critical decision making. 

For instance, environmental groups focus much of their attention on the potential damage to microbes, bacteria, and other very small organisms caused by the tracks of a harvesting vehicle or its harvesting head.  Yet microbes and other small organisms can be impacted as much or more by the blasting, drilling, and compacting of soil from terrestrial mining operations.  We don’t, however, see anti-mining activists protesting against the damage done to microbes due to soil compaction in terrestrial mines.  This is because the deforestation, mountain top removal, acid mine runoff, toxic waste, and negative human health consequences often associated with terrestrial mining are so much worse for society.  Because NGOs lack a yardstick to measure impacts, they cannot properly contextualize the relatively small costs from harvesting.  It is important that society makes important decisions based on a critical assessment of all of the information available, not based on a one-sided view that omits the most important considerations. 

Opposition to deep sea nodule harvesting generally falls into one of two categories: 

1. Nodule harvesting causes serious and irreversible long-term damage to the environment through several different pathways. 
2. There are too many unknowns with respect to nodule extraction.  We are therefore better off avoiding commercial extraction until these unknowns are better understood. 

Both points have a small amount of validity, but they lack context.  When proper context is added it becomes clear that neither of these arguments should preclude nodule harvesting from moving forward today. 

Regarding the first point, just about any form of natural resource extraction causes serious and irreversible harm.  Yet, when nodule harvesting is compared with terrestrial mineral extraction for the same minerals, the evidence strongly suggests that nodule harvesting creates dramatically less environmental and social damage.  This is demonstrated in three detailed lifecycle analyses referenced later and is further supported by empirical data and logic provided in the following pages  ( Batker & Schmidt, 2015) (Benchmark Mineral Intelligence, 2023) (Paulikas, 2022).

In answer to the second point there are several counterarguments, three of which are provided below:

• While there is uncertainty related to the impacts of nodule extraction there is considerable certainty surrounding the fact that related impacts are not as damaging as those associated with terrestrial mining.  The physical characteristics of nodule extraction, the limited biomass & biodiversity found in the abyssal plains relative to terrestrial settings, and the relatively small footprint of impacts from harvesting compared to the size of nodule rich plains, together place limits around potential damage from harvesting.  Those limits are well within the bounds of environmental and social damages defined by terrestrial mining as will be developed later.
• There is considerable uncertainty around threats to biodiversity from terrestrial battery mineral mining in tropical rainforests.  Rainforests are the most biodiverse and sensitive habitats on the planet, and millions of rainforest species have yet to be discovered.  We don’t understand the threat that mining poses to this ecosystem because we don’t understand the ecosystem (~86% of rainforest species are yet to be discovered).  (Mora, 2011) Yet, we continue to mine rainforests for battery minerals despite the unknowns and despite the fact that terrestrial mining does more harm to rainforests than nodule harvesting does to the abyssal plains (a point developed later).
• Scientists have studied nodule harvesting impacts for over 45 years, so a lot is known in terms of impacts, and those impacts have been shown to be far less intense than those seen in terrestrial mine. (Gausepohl, 2020)  In fact, a study of The Metals Company 2022 harvesting campaign showed that harvesting decreased biodiversity by 20% in the crawler’s track while biodiversity was unaffected in the plume zone. (O’Malley, 2023)   

Environmental opposition groups propose to ban or impose a moratorium on nodule extraction, but the reality is that this represents a dangerous and high-risk pathway.  Such actions promote the status quo which means leaning into a reliance on Chinese mining firms and their extraction programs which are often the costliest to the environment, the dirtiest, and have the most negative impacts on humanity.  Those costs will accelerate in the future as the strip mining and blasting soars to meet decarbonization goals while terrestrial ore grades continue to decline.  Declining ore grades dictate that every unit of metal created becomes more costly economically, environmentally, and socially, as mining outfits must dig deeper into the most pristine and sensitive habitats on the planet to unearth new battery minerals.  This suboptimal course will undermine efforts to gain societal “buy-in” for the energy transition and could ultimately delay or even halt the transition entirely as costs continuously increase with declining grades.

Terrestrial Mining vs. Nodule Harvesting

Most everyone agrees that the energy transition’s call for a significant increase in primary mineral production be satisfied in a manner that achieves the largest benefit to society with the least environmental and social damage.  Understanding how to maximize efficiency to achieve these ends requires comparative analyses of different proposed solutions.  Operations must be benchmarked against each other, or against a current operating standard, in order to understand which have the potential to increase efficiency and thus minimize costs (environmental, social, and economic).  Comparative analysis is a fundamental component of critical thinking, and studies that lack this type of analysis provide little utility. 

Unfortunately, the environmental NGOs which oppose harvesting have generally avoided comparisons between nodule extraction operations and benchmark terrestrial operations.  These groups assess the risks of nodule harvesting in isolation, as absolutes, without the benefit of a yardstick.  The lack of yardsticks causes environmental groups to arrive at faulty conclusions that can steer society in the wrong direction. 

Consider the risks from harvesting that these groups often cite as most dangerous – the physical destruction caused to organisms on the ocean floor from the harvester’s direct impact, and the potential suffocation of stationary organisms from the bottom-water plume created by the harvester.  Each of these impacts (direct impact from mining equipment and plumes) is worse in a terrestrial setting (a point developed later in this section), but we generally ignore them because the other impacts from terrestrial mining (poisoning of people, deforestation, watershed destruction, toxic waste, etc.) are more consequential.  Yet, the more consequential impacts from terrestrial mining are completely absent from nodule harvesting operations.  Thus, even though the worst impacts from harvesting are more dangerous in terrestrial mines, and even though the worst impacts from terrestrial mines are not present in harvesting operations, NGOs ignore these facts due to the faulty construct of their logic. 

NGO claims that there are too many unknowns with respect to nodule harvesting are cast in a different light when we use comparative analysis.   The use of unknowns is a strategy regularly employed by environmental groups to halt projects through reference to the Precautionary Principle.  That Principle holds that a project should not be undertaken when there is the potential for significant harm, but uncertainty remains with respect to evidence for the negative consequence. 

Research is constantly being undertaken to understand the impacts of both terrestrial and deep-sea mining, but unknowns will always persist – we will never have perfect information.  Though terrestrial minerals have been mined for hundreds of years, new information on impacts is still emerging.  For instance, it was only recently discovered that certain worms and microbes exist miles below the earth’s surface and can be compromised during overburden removal.  Indeed, scientists from the Deep Carbon Observatory have ascertained that greater genetic diversity exists below the surface of the earth than above (Venton, 2018).  Moreover, approximately 86% of species in the world are yet to be discovered, and with half of the world’s species thought to be in tropical rainforests, clearly millions of rainforest species remain unidentified and risk extinction due to mining. (Mora, 2011) We cannot hope to understand the direct and indirect impacts of mining in tropical rainforests if we cannot identify 86% of the life that exists in the ecosystem.  Yet, this uncertainty hasn’t stopped us from mining battery minerals in the world’s most sensitive habitat because the benefits of mining outweighed our probabilistic risk assessment of the unknowns.

The lack of complete and perfect information should not prevent society from acting appropriately on the considerable information that is available.  In the case of extracting transition minerals, sufficient information exists today to support, with a high degree of confidence, the claim that deep sea nodule extraction comes with fewer environmental and social risks than does terrestrial mining – especially terrestrial mining by Chinese firms.  A precautionary approach to extracting minerals would note the substantial risks involved in continuing to source minerals from terrestrial mines, with their relatively high environmental and social costs, when nodule extraction can avoid or reduce many of these costs.   A precautionary approach to harvesting nodules will employ best practices which minimize environmental impacts while using the best available technology. 

Consider the following comparisons between nodule harvesting and terrestrial mining: 

1. Open pit mines (strip mines) are the most prevalent form of terrestrial mines around the world and are also particularly environmentally destructive. (MIT, 2016) The practice involves removing large quantities of overburden to get to the targeted minerals.  Removing overburden usually means total deforestation, or removal of grasslands or wetland ecosystems, and is thus considered one of the most environmentally costly aspects of mining. (eLaw, 2022) It means digging, drilling, or blasting deep into the ground and compromises not only biomass living above ground but deep underground as well.  The process is also energy-intensive, creating meaningful CO₂ emissions. Exposed overburden often contains rock sulfides and radioactive elements which frequently drain into waterways.  According to one study, 92% of mines failed to control wastewater which led to widespread contamination. (Earthworks, 2012)  Contamination of watersheds from mining is said to impact at least 24 million people today (Macklin, 2023).  By contrast, deep sea nodule extraction does not require any overburden removal and thus avoids entirely one of the most, if not the most environmentally and socially costly, aspects of mining. 
2. Once a terrestrial mine’s overburden is cleared, the operation begins to excavate the ore-bearing rock.  This usually requires blasting or cutting out the desired strata of the formation.  That ore-bearing rock is then loaded into trucks and transported to a processing station.  The first step of processing usually involves crushing, grinding, filtering, and sometimes treating the mixture to extract the targeted mineral. The targeted mineral often exists in minute quantities within the pay mixture – often between 0.5% and 2% of the rock. This means that ~99% of the rock that is blasted, extracted, transported, processed, and then disposed, is pure waste.  Moving, processing, and storing large quantities of waste rock is energy intensive and is often very environmentally damaging.  With nodule harvesting, the ore-bearing rock contains 100% commercial minerals.  This means that another one of the most damaging aspects of mining – extracting, processing, and disposing of waste ore – is completely or almost completely eliminated in nodule harvesting.  In addition, because nodules are highly friable (they break apart easily), grinding them requires far less energy than that associated with hard rock terrestrial deposits.  Grinding and milling is one of the most energy intensive aspects of mining, so the environmental/cost savings from higher friability are significant. 
3. Terrestrial mines generally produce only one or two different types of commercial mineral products while a nodule extraction operation will produce between 5-7 different commercial minerals.  Thus, a single nodule extraction operation can replace the production from 2-3 terrestrial mines.  Because a nodule operation will not require overburden removal, the savings in terms of habitat destruction and mine waste from not having to open many different mines are significant.     
4. Marine Biologist Gerald McCormack of the Cook Island Government’s National Heritage Trust calls the Cook Island nodule fields “the largest oceanic desert on earth” due to the low productivity of the waters in the area and the resulting low biomass and carbon found on the sea floor. (McCormack, 2022) While the nodule fields host some biodiversity (though far less than rainforests), the damage done removing nodules is limited by the small scope of the extraction operations (estimated to impact ~7% of the dense nodule fields over 50 years) and the extremely limited biomass.  Contrast this with nickel, cobalt, manganese, rare earth, and copper mines around the world and you will find that these mines often exist in areas of not only very high biomass, but also exceptionally high biodiversity. (Sonter, 2020)  In short, the threat of loss of biodiversity appears to be far higher in terrestrial battery mineral mines than in nodule extraction operations. Biodiversity is discussed in detail in another section of this website. 
5. Because nodules are generally inaccessible except to large, well-funded groups with a high level of expertise and technical equipment, and because nodule processing is highly specialized, governments and regulators will be able to track production & processing much more easily than is the case with terrestrial mining.  This will allow greater oversight than is practical in terrestrial mining, and it means that these operations will be well regulated and should not suffer from the poor/inhumane labor conditions, minimal environmental oversight, and weak supply chain transparency often associated with certain terrestrial minerals. 

The comparative case to advance nodule extraction on environmental and social grounds extends further.  Nodule extraction does not require any freshwater use, no relocation of humans, no encroachment on habitats humans use for sustenance (other than vessels in fishing areas), no permanent infrastructure on sensitive habitats (such as roads, electric power distribution, housing, or on-site processing), no introduction of toxic chemicals into the environment, no airborne pollutants that cause respiratory disease in humans, and no need for tailings dams.  Terrestrial mines often entail these risks, and many more, when indirect impacts are included. 

While nodule harvesting avoids many of the most serious environmental costs associated with terrestrial mining, we might still want to avoid harvesting if the benefits of avoiding environmental costs are offset with risks of serious harm that are unique to harvesting.  In other words, does nodule harvesting cause damage that is exclusive to the practice and avoidable by remaining solely dependent on terrestrial mining?

Nodule harvesting entails the removal of nodules that have formed over tens of millions of years.  All organisms that are hosted on those nodules will be lost (just like organisms in overburden and ore from a terrestrial mine).  It is also true that some mobile organisms which depend on animals that are hosted on nodules for food, or to host eggs, could be lost.  We would note, however, that nodule harvesting would impact far less than one percent of the nodule rich abyssal plains over twenty years, so this risk is limited.  We also note that harvesters will be configured to leave some nodules in place to encourage recolonization, and that large set aside areas (as much as 30% or more of the license) will be created where nodules are untouched.  In addition, only 13% of the species in the CCZ are known to be primarily nodule dwellers so it is likely that a relatively small amount of species would be impacted. (Rabone, 2023)

We should also emphasize that the amount of biomass lost to the activity will be small in comparison to the losses from terrestrial mining activities because the levels of biomass on the abyssal plains are as much as 3,000 times lower than those found in tropical rainforests. (Bar-On, 2018)  Low productivity top water translates to low biomass at the bottom of the ocean.  In addition, the extreme pressure, complete lack of sunlight, and low temperatures at the depth of the abyssal plains mean that few of the sea animals commonly known to man exist in the environment.  There are sponges, small sea cucumbers, a variety of worms, small starfish, as well as tiny microbes present, but common pelagic sea life does not depend on nodules or their environment.  The majority of life on the abyssal plains is either microscopic or is barely visible to the human eye. (Rabone, 2023)  By comparison, the environment destroyed in terrestrial mining is rich in biomass and biodiversity, and many common animals (including humans) depend on it for survival. 

Nodule harvesting will compromise some organisms that live in the sediment around the nodules.  According to biologist Gerald McCormack, however, the organisms resident in these sediments are not unique to dense nodule habitats and are found in sediments throughout the abyssal plains, making their loss less concerning. (McCormack, 2022)  Even if these animals were unique to dense nodule habitats, the fact that nodule harvesting over 20 years will compromise a very small proportion of the abyssal plains is reassuring.  As discussed in the section on biodiversity, long-term studies have shown that harvesting an area will not destroy all of the animals that are resident, though it will reduce their numbers and cause a relatively small decline in the level of biodiversity (20% reduction according to recent work).  These long-term studies also reveal that over 30-40 years, diversity levels rebound, and in some cases exceed baseline.   Biodiversity and biomass is usually completely destroyed in a strip-mine footprint.   

Related to the point above is the fact that nodule harvesting will cause plumes at the seabed which have the potential to suffocate organisms on the seafloor and on nodules if enough sediment is deposited on top of them.  This said, researchers have spent considerable time studying bottom-water plumes to characterize them and understand a great deal about their potential for damage (Fukushima, 1995) (Xie, 2003).   According to a number of studies, the damage from plumes is relatively contained because of the tendency of plume sediment to rapidly flocculate, especially in environments with high shear velocities (bottom water currents).  In addition, evidence from harvesting operations suggests that sea life within a plume zone will not be adversely impacted.  A study which followed active harvesting in the CCZ during a 2022 campaign has shown that plumes do not impact the density or diversity of sessile benthic creatures (foraminifera), so we believe this risk is not significant. (O’Malley, 2023)

Our findings suggest that the use of elevated sediment discharge (500 mg L–1) under elevated turbulence results in rapid sediment flocculation. The modeling results also suggest that mining under “typical” deep-sea flow conditions results in a relatively rapid deposition of larger particles from the plume, thus restricting the blanketing effect to a smaller fall-out area  (Gillard, 2019)

While some studies note that plumes can extend tens of kilometers, the levels of concentration of sediment in longer plumes is relatively low as compared with background baseline (Spearman, 2020).  In addition, neither plumes nor the water that carries them are able to migrate into upper layers.  Bottom waters on abyssal plains are cold and dense, and travel along the ocean bottom.  When they encounter obstacles, they move around them on their migration, not over them. (McCormack, 2022)

In the first study that assessed plume characteristics from a prototype collector operating on the abyssal plains of the CCZ, the authors noted that only 2-8% of the sediment disturbed was observed at a height over two meters from the seabed and hadn’t settled over several hours. (Peacock, 2022)  These findings were further confirmed by empirical data from a harvesting operation run by TMC in 2022. Link

Readers should note the important distinction between bottom-water and mid-water plumes.  Bottom-water plumes result from collection vehicles disturbing sediment as they harvest nodules.  Mid-water plumes are created when sediment and water is brought to the surface using riser pipes and is then disposed by pumping the mixture down an outflow pipe to a depth of approximately 1,200 meters.  The mid-water plume is seen as more troublesome because it is likely to travel greater distances than a bottom-water plume and because it has the potential to impact pelagic species due to its release point being close to these species’ habitat.  Contractors who employ the use of risers are in the process of engineering new return systems that will return sediment and seawater all the way to the bottom rather than releasing at midwater depths. Other systems avoid the need for risers and any sediment return from the surface vessel.

It is telling that environmental groups focus so much attention on nodule extraction plumes.  Terrestrial mines also create plumes that travel far greater distances than bottom water plumes due to the low friction in earth’s atmosphere. (Khan Academy)  Large particles are known to travel over 10,000 km, and create far greater risk to human health and the environment than do bottom water plumes (which have no known mechanism for impacting human health or the greater human food web). (van der Does, 2018) (Entwistle, 2019) (Patra, 2016)   Terrestrial mines inject large amounts of particulate matter into the air due to the extensive removal of overburden and the large amounts of waste rock that they generate – risks not associated with nodule harvesting.  Airborne pollutants are known to cause a variety of respiratory diseases, cardiovascular diseases, and even neurological diseases in mine workers and in communities nearby. (Entwistle, 2019)

The fact that airborne terrestrial mine pollution (plumes) from particles is far down the list of concerns with respect to terrestrial mining impacts is revealing.  It signals that the other impacts from mining (overburden removal, mining runoff, introduction of toxic agents, fresh water contamination and use, tailings dams risks, etc) are perceived to have a greater impact on society and the environment.  Yet plumes are at or near the top of the list of concerns with respect to nodule harvesting, even though their potential to do harm appears to be significantly lower than plumes associated with terrestrial mining.  The level of concern around bottom water plumes is thus instructive mostly because it provides a measure of the lack of strength in environmental arguments against nodule harvesting. 

Environmental groups allege that noise and light from harvesting operations will compromise ocean ecosystems.  The noise that is likely most troublesome to these groups may be that which is associated with riser systems and pumps.  The transporting of nodules through a riser will cause clanging and the pumps that are located along the riser system will create noise as well.  In particular, there is a channel of depth in the ocean (SOFAR channel) where certain low frequencies can travel great distances and may distract whales that enter that sound channel. But the noise from harvesters and risers should not vary appreciably from the systems used today to dredge aggregates or lift oil in shallower, more sensitive environments. Moreover, alternative lift systems don’t use risers or pumps, so this risk is avoided in those systems.   

While noise and light will be present in a nodule extraction operation, biologist Gerald McCormack reports that bottom dwelling creatures use light in the blue/green spectrum to communicate with and identify others, so as long as the light avoids those wavelengths, it should not be problematic. (McCormack, 2022) Noise from operations in bottom waters and on the surface will impact the ecosystem, but these impacts would be no greater than the impacts from all of the bottom trawling fishermen or dredging operators who operate year-round throughout global oceans.  Equipment will be specially designed to minimize noise impact, and studies have demonstrated that mobile species tend to avoid unpleasant noise and light as would be expected.  Terrestrial mines often involve blasting and digging which usually create significantly more noise than a harvesting operation, so replacing these impacts can create net benefits to humanity and the environment. 

In summary, we find little evidence to support the argument that risks unique to harvesting operations would offset the substantial benefits from employing nodule harvesting to eliminate or minimize some of the damage that is common in terrestrial mining.   The evidence and logic presented here provide a compelling rationale to progress trial harvesting so that the claims in support of nodule harvesting can be strengthened (or retracted if necessary). 

Comparative Life Cycle Analyses

We highlight three studies below which are the only comprehensive reports comparing the life cycle costs and benefits of deep-sea mining to those of terrestrial mining.  Each of them concludes that deep sea mining is less impactful to human health and to the environment than terrestrial mining.  What is most interesting, however, is the size of the differential between impacts.  These analyses cite reductions in impacts on the order of 75-99% across a number of categories.  

Earth Economics was commissioned by Nautilus Minerals to measure the difference in social and environmental impacts in three terrestrial copper mines against Nautilus’s proposed seabed mining operation, Solwara 1. (Batker, 2015) The Earth Economics study followed the methods of the United Nations Environment Program in applying natural capital valuation to compare the impacts of mining extinct hydrothermal vents off the coast of Papau New Guinea versus the three terrestrial mines.  The study concluded that the seabed operation would reduce environmental and social costs associated with mining by 70-95% as compared with the terrestrial counterparts. 

Comparison of Solwara 1 hydrothermal vent extraction impacts versus three terrestrial copper mines

Source: Earth Economics, 2015

Despite its favorable comparison versus terrestrial copper mines, it is worth noting that Nautilus’s proposed Solwara 1 mine would have been far more destructive to the environment than a nodule harvesting enterprise on a per unit extracted basis.  The extraction processes to remove hydrothermal vents from the ocean bottom requires significant earth moving and invasive cutting operations to detach the ore body while nodule harvesting does not.  In addition, the environment around the Solwara 1 site was more sensitive than the abyssal plains.   The hydrothermal vents were located in waters that were shallower than the abyssal plains (around 1,600 meters vs. 5,000+ meters on the abyssal plains) and the topography of the vent sites tends to attract abundant sea life while biodensity is limited on the abyssal plains. 

In a fairly comprehensive study commissioned by The Metals Company, a life cycle assessment analysis and ecosystem analysis were undertaken to understand potential economic, social, and environmental impacts from nodule harvesting versus terrestrial mining (Paulikas, 2022).  The study concluded that nodule harvesting would produce better outcomes for society with respect to a number of different impacts versus terrestrial mining. 

Environmental, Social, and Economic Impacts of Land vs Nodule Sourced Minerals

Cradle-to-Gate Production of Nichel Sulfate, Manganese Sulfate, Cobalt Sulfate and Copper Cathode for 1 Billion Electric Vehicles

	Land	Nodules	% Change
Climate Change
GWP – CO2 equivalent emissions, Gt	1.5	0.4	-70%
Stored carbon at risk, Gt	9.3	0.6	-90%
Nonliving resources
Ore use, Gt	25	6	-75%
Land use, km2	156,000	9,800	-94%
Incl. Forest use, km2	66,000	5,200	-92%
Seabed use. km2	2,000*	508,000	+99.6%
Water use	45	5	-89%
Primary and secondary energy extracted, PJ	24,500	25,300	+3%
Waste Streams
Solid waste, Gt	64	0	-100%
Terrestrial ecotoxlclty, 1,4-DCB equivalent Mt	33	0.5	-98%
Freshwate, eootoxiclty. 1 ,4-DCB equivalent Gt	21	0.1	-99%
Eutrophlcatlon potential, P04 equivalent Mt	80	0.6	-99%
Human & wildlife health
Human toxicity, 1 ,4-DCB equivalent Mt	37,000	286	-99%
SOx and NOx emissions, Mt	180	18	-90%
Human lives at risk, number	1,800	47	-97%
Megafauna wildlife at risk, trillion organisms	47	3	-93%
Biomass at risk, Mt	568	42	-93%
Biodiversity loss risk	Present	Present
Economic Impact
Nickel sulfate production cost, USD per tonne Ni	14,500	7,700	-47%
Jobs created (non-artlsanal), worker-years	600,000	150,000	-75%

These better outcomes include a reduction of Global Warming Potential (GWP) impacts by 70%, and a reduction of carbon sequestration release by 94% versus sourcing battery minerals from terrestrial mines.  The study also cited a 98%+ reduction in waste streams, and a 93%+ reduction in risk to megafauna, biomass, and human toxic exposure.  It estimated a ~90% reduction in land and water use vs. terrestrial mining. 

On the negative side, nodule harvesting would create fewer jobs (though the jobs would be safer) and would require a 100% increase in seafloor use.   

In the third study, Benchmark Minerals Intelligence completed a life cycle assessment of the environmental impacts of The Metals Company’s NORI-D polymetallic nodule project and compared those impacts to terrestrial mining routes for the same end products. (Benchmark, 2023)  The study was reviewed by an independent third-party expert for accuracy and compliance with applicable standards.  It showed that the NORI-D project performed better in each impact category analyzed with the exception of global warming potential, where one of TMC’s products (cobalt sulfate) placed second. 

The three studies are noteworthy not only for the fact that they each conclude that deep sea extraction can lead to reduced environmental and human impacts from mineral extraction, but for the fact that the size of the implied improvements are impressively large according to each of these LCA’s.  Even if we assume a substantial margin of error and consider the remaining uncertainty around harvesting (and the remaining uncertainty around terrestrial mining), it is reasonable to presume that careful extraction of nodules can create meaningful net benefits to society and the environment versus terrestrial mining. 

Such large improvements in environmental and human health impacts related to mineral extraction are certainly important.  The industrialized world is pursuing a decarbonization strategy that will demand an unprecedented expansion of mining activities.  Whether there are sufficient terrestrial resources for some of the critical minerals involved is an open question if we consider not only mobile and fixed energy storage systems, but also grid buildout, EV charging infrastructure, electrification of industrial power, and renewable energy generation mineral demands.  Regardless of whether adequate terrestrial resources exist, we know for certain that developing new land-based mines to meet the increased demand will mean going deeper into unpopulated, highly sensitive ecosystems in an increasingly invasive manner to extract ever decreasing grades of ore.  As terrestrial grades decrease, costs increase, and resources deplete, each pointing to a higher economic burden that could easily threaten an energy transition   There is a way out of this tight spot – a massive resource exists which can be accessed while doing far less damage to the environment and to human health.  Polymetallic nodules should be viewed as a gift to society.