A Techno-Economic Assessment of Seabed Mining: American Samoa and Global Implications – CleanTechnica

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Seabed mining has moved from the fringes of resource speculation into the center of debates about critical minerals, national strategy, and global environmental governance. Proponents frame it as an essential solution to future nickel, cobalt, copper, and manganese supply, while opponents highlight the biological risks, the regulatory uncertainty, and the long record of first-of-a-kind offshore projects that failed to meet their promises. Into this messy set of claims and counterclaims comes A Techno-Economic Assessment of Seabed Mining, a study commissioned by the National Ocean Protection Coalition. The assessment was prepared by myself and metallurgical engineer Lyle Trytten to answer a basic question. Is seabed mining in the American Samoa region economically viable and technically achievable?

The National Ocean Protection Coalition brings together more than 90 organizations to create and support marine protected areas and place-based ocean protections in the United States. The coalition includes groups representing national, regional, and local perspectives from across the U.S. and includes Indigenous leaders, scientists, faith leaders, conservationists, outdoor enthusiasts, fishers and more. NOPC is supported by philanthropic foundations and partner organisations.

NOPC commissioned the study because the gap between public claims and grounded engineering has widened. Supporters of seabed mining often point to future shortages of battery metals or global supply chain pressures without acknowledging that many of these claims depend on optimistic projections about demand, slow growth in recycling, weak performance of recycling, limited minerals substitution, and weak performance of terrestrial mining. NOPC needed a neutral view that started with the hardware, the supply chains, and the markets, rather than the marketing. They are funding other studies on the environmental concerns from appropriate and credentialed experts. The coalition’s role in pushing for transparent, independent evaluations of ocean uses made this request a natural extension of their work.

The report begins with the basic geology. Polymetallic nodules accumulate slowly over millions of years in deep ocean basins. They contain manganese, nickel, copper, cobalt, iron, and trace elements. The grades vary widely across the Pacific and Indian Oceans. Published data shows that nodules from the Clarion Clipperton Zone have different compositions from nodules in the Cook Islands, Fiji Basin, Indian Ocean, Gulf of Cadiz, and the Baltic Sea. The nearest analogue to American Samoa is the Cook Islands region, which has lower nickel and higher iron and cobalt than the CCZ. The lack of detailed local sampling in American Samoa means that any financial model built on CCZ grade assumptions is speculative at best.

Two distinct technological approaches are competing for attention. Impossible Metals proposes a fleet of autonomous underwater vehicles that pick up nodules with robotic arms while attempting to avoid sediment disturbance. Their Eureka series AUVs are presented as light touch machines that can cycle every few hours, return to the surface, unload, swap batteries, and go back down. The Metals Company, by contrast, uses a conventional tracked crawler that vacuums nodules into a slurry and pumps them up a vertical riser to a production vessel. Both approaches claim scalability. Both come with steep engineering risks.

A detailed TRL assessment shows how far from investable solutions the two systems actually are. The IM system contains multiple subsystems at TRL 3 to 4. These include multi-robot coordination at depth, high throughput picking, automated launch and recovery for dozens of robots in rolling seas, and sustained operations at 4,000 to 6,000 meters. Even if each subsystem improves steadily, the combined system inherits the lowest TRL. The overall integration sits at TRL 3 to 4, which is typical of research prototypes. The Metals Company’s system has higher maturity, at TRL 6 to 7 for the crawler and riser components and TRL 8 to 9 for the support vessel, slurry handling, and bulk shipping. That puts it closer to a pilot system, but still far from commercial reliability.

This matters because deepwater projects follow predictable patterns. Bent Flyvbjerg’s work on megaprojects, which covers over 16,000 global projects, shows that first of a kind systems suffer long delays, high cost overruns, and optimistic early forecasts. Offshore and subsurface systems are especially vulnerable, because they combine complex logistics, harsh environments, and intricate mechanical systems. The pattern is familiar. Nautilus Minerals never got its Papua New Guinea project into production. GSR’s Patania II collector became stuck during testing in the CCZ. Deepwater drilling systems often require years of tuning before they reach nameplate performance. There is nothing in the seabed mining proposals that would invert these patterns.

Cost analysis provides a useful lens on the companies’ claims. IM projects vessel costs of $40 million and per-robot costs of about $3 million. Overlapping estimation approaches based on Flybjerg’s reference class forecasting and sensitivity analysis shows that a vessel capable of carrying, charging, deploying, repairing, and storing 90 deep rated heavy AUVs would be closer to $80 million to $120 million if built in Asia or Europe, with higher costs in the U.S. Each Eureka IV robot, with 18 manipulators, deep rated housings, 400 kWh batteries, onboard storage, precision navigation, acoustic positioning, and multi-arm coordination, is more realistically in the range of $10 million to $14 million. A full fleet could cost several billion dollars before operations begin. Operating costs would also be higher than forecast. Battery cycling, thruster wear, arm maintenance, spare parts, and crewed operations on a large vessel drive ongoing expenses well above the company’s public projections.

The Metals Company shows the same pattern, although with more mature hardware. The company initially projected offshore collection costs of roughly $36 per wet ton. Independent benchmarks and Allseas’ own figures show that real offshore collection costs are closer to $113 to $170 per ton. Their recently released prefeasibility study now aligns with higher figures. These numbers reflect the cost of pumping abrasives through long risers, maintaining subsea pumps, replacing riser sections every few years, running a DP vessel for long stretches, and accepting lower uptime during early operations. Offshore energy projects generally operate at 80% to 90% uptime only after substantial learning periods, and new subsea systems often start closer to 60% to 70%.

Processing is another limiting factor. There is no commercial scale nodule processing facility today. Two broad routes exist. Smelting through rotary kiln electric furnaces can produce a manganese silicate and a nickel copper cobalt matte. High pressure acid leaching can recover nickel, copper, and cobalt into solution, but leaves manganese behind as waste. Both require new infrastructure.

The track record for new nickel and cobalt processing plants is poor. HPAL facilities in Australia, Madagascar, and New Caledonia suffered long ramp ups and major losses. Even well funded, well designed Western projects have struggled to reach stable output. China’s build out of processing lines in Indonesia succeeded only by repeating the same plant designs over and over with a large labor force and state backing. Nothing similar exists in the U.S. today. Any domestic facility would face long timelines, high risk of delay, and a shortage of necessary specialized labour.

Market conditions further weaken the economic case. Nickel demand is projected to rise under some energy transition scenarios, but Indonesia and China dominate supply growth. Many Western forecasts about shortages have underestimated the speed and scale of Indonesian output. Cobalt demand is expected to peak by 2040 under the IEA’s Announced Pledges Scenario, and currently planned supply covers most future needs. Copper demand shows a potential gap, but nodules cannot fill it without creating massive oversupply in manganese, nickel, and cobalt. A single large nodule project could add almost 10% to the global manganese supply, pushing prices down, a clear problem with the economic viability as there is far more manganese in nodules than anything else, 15% to 30% of dry mass, so the price it can receive strongly impacts any return. More than one project would likely cause manganese prices to collapse, destroying the business case. Recycling will play a growing role as stocks of stainless steel, wiring, electronics, and batteries return to the supply chain. These changes reduce long term upside for seabed metals.

Environmental and market acceptance risks add to the picture. Germany, France, New Zealand, and several Pacific nations have called for pauses on deep sea mining. Large manufacturers including BMW, Volvo, Samsung, and Google have pledged not to use seabed minerals. Battery manufacturers are especially sensitive to supply chain pressure. A project may be technically able to produce nickel and cobalt, but find limited buyers for the output at premium prices. Shipping intermediates through Chinese controlled facilities adds strategic constraints for U.S. interests. American Samoa also faces reputational risks if it becomes a center for a contested extractive industry.

The fiscal sensitivity analysis illustrates how these factors interact. Using realistic productivity assumptions for the AUV fleet and more grounded nodule valuations in the range of $100 to $250 per ton, internal rates of return range from below 0% to 36%. Net present values range from negative $4.8 billion to positive $5.8 billion at a 10% discount rate. The negative cases are not edge cases. They are well within the range of scenarios expected when low TRL systems, unproven processing, and volatile metal markets intersect. The bubble charts generated in the analysis show that many combinations of nodule value and productivity sit firmly in the negative region. The optimistic cases sit at the top of the distribution, not the middle.

For American Samoa, the implications are significant. Any seabed mining project would operate near ecologically sensitive areas with minimal local data about benthic conditions. It would require heavy vessels, offshore logistics, and onshore storage and handling. It would expose the territory to market fluctuations, international scrutiny, and long periods of financial uncertainty. The potential upside is real but conditional, while the downside involves high tail risks that would fall disproportionately on local waters and communities.

The assessment concludes that both major approaches are unlikely to achieve commercial success. IM remains at an early prototype stage with major uncertainties across all critical systems. The Metals Company has a more mature approach but faces cost inflation, slow ramp ups, and difficulty matching published numbers. Policymakers should require independent verification of all techno economic claims, strong environmental safeguards, and transparent risk assessments before considering any extraction. Strategic planning should focus on terrestrial mining partnerships, expanded recycling capacity, and long term agreements with allied producers rather than dependence on an unproven offshore sector.

Seabed mining is often framed as a race. In practice, it is a long series of engineering and economic hurdles with uncertain rewards that’s competing with much lower risk terrestrial mining, recycling and minerals substitution. For stakeholders in American Samoa and beyond, the responsible path is one grounded in technology readiness, realistic market evaluation, and the historical record of similar projects. The goal should not be to stop innovation but to ensure that decisions reflect the actual state of the science and engineering, not the confidence of the proponents.