As the race to achieve net zero by 2050 continues, the demand for rare earth metals essential for low-carbon energy and transportation is rising. However, extracting these metals on earth has become increasingly challenging, often leading to deforestation, habitat destruction, and biodiversity loss. Deep-sea mining offers a promising alternative, albeit with concerns about its environmental impact and long-term feasibility.
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Understanding Deep Sea Mining
Deep sea mining involves extracting mineral resources from the seabed using hydrodynamic or mechanical methods. It also uses vertical lifting equipment, seabed mining vehicles, production support vessels, and bulk vessels to collect and transport the minerals.
The key economic incentive driving commercial interest in deep-sea mining is the increasing global demand for battery metals, such as nickel, cobalt, manganese, and copper, coupled with their growing scarcity on land.
The deep ocean seabed holds vast ore deposits of these metals that could meet global demand for hundreds, if not thousands, of years.
The three main types of resources targeted for deep-sea mining are:
- Polymetallic nodules - these potato-sized mineral formations containing manganese, nickel, cobalt, and copper are found on the abyssal plains of the ocean floor at depths of 4000-6500 meters.
- Cobalt-rich ferromanganese crusts - these thick crusts form on the flanks of seamounts (underwater mountains) at depths of 800-2500 meters and contain high concentrations of cobalt, nickel, manganese, tellurium, and platinum.
- Hydrothermal vents - these areas, characterized by the emergence of heated, mineral-rich water from beneath the ocean floor, are known for their abundant reserves of sulfides, gold, silver, and rare earth elements. The vents are located along mid-ocean ridges at depths of around 2000 meters.
Although deep-sea mining was initially proposed in the 1960s, numerous technological and environmental challenges have limited its widespread industrialization.
Technological Challenges of Deep-Sea Mining
The primary challenge in developing mining technology lies in upscaling and integrating subsystems for year-round operation in harsh deep-sea conditions, such as hydrostatic pressure of 500 bars, cold temperatures of 1-2 °C, complete darkness, uneven terrain, complex currents, and varying mineral distributions.
Developing automated or remotely controlled continuous mining systems will also be critical since sending human crews and divers thousands of meters deep for long stretches is not feasible.
Artificial intelligence, robotics, autonomous navigation, and other technologies can help enable this transition, but they are still evolving for deep ocean applications.
Another major obstacle is to deliver adequate energy to fuel deep-sea mining systems, whether via seafloor power cables, onboard generators, or renewable sources.
Lastly, significant technological advances are required in seabed crawlers, pumping systems, riser pipes, and vertical lifting systems to continuously and reliably extract and transport thousands of tons of ore daily from the seafloor to the surface platform.
Environmental Concerns of Deep-Sea Mining
While deep-sea mining could yield substantial economic benefits by providing a new source of essential metals, it poses potentially serious environmental risks and impacts.
Deep-sea habitats hosting polymetallic nodules, cobalt crusts, and sulfide deposits offer vital ecosystem services and support unique biological communities with numerous endemic species. Many of these species have evolved unique adaptations to extreme conditions, and these environments often take millennia to form.
Direct physical destruction and removal of seabed resources that organisms rely on would be an inevitable impact. Mining activities would also generate noise, vibrations, and sediment plumes that could have far-reaching effects on the sea floor and water column habitats. In addition, light and noise pollution could impact marine mammals' behavior and communications over long distances.
The release of toxic metals, hydrogen sulfide, and other substances from sediments and mining waste could contaminate surrounding waters, potentially leading to bioaccumulation up the food chain and further dispersion by ocean currents, extending beyond mining sites.
An MIT study has revealed that sediment in deep-sea mining plumes disperses rapidly due to turbulent discharge rather than settling as expected. This highlights concerns about the potentially extensive environmental impact of mining waste.
Small-scale disturbance experiments, like 1970s polymetallic nodule mining tests in the Clipperton Fracture Zone, showed measurable negative impacts on deep ocean organisms. As a result, scaling up to full commercial operations without improved environmental regulation could be disastrous for vulnerable deep-sea ecosystems.
The International Seabed Authority (ISA) regulates deep-sea mining activities in international waters under the United Nations Convention on the Law of the Sea (UNCLOS). The ISA issues licenses for exploration and will establish regulations and requirements for the environmental management of seabed mining.
However, some experts argue that current ISA rules are insufficient to protect vulnerable deep ocean environments and biodiversity. Critics contend revisions are needed to mandate more comprehensive environmental impact assessments, increased transparency from mining companies, and greater ISA accountability.
Sustainable Practices and Alternatives
Companies are investigating sustainable technologies for deep-sea mining, including precision AI-guided robotic arms for delicate nodule harvesting and hybrid air/electric underwater drones to selectively collect minerals without disturbing seabed ecosystems.
Other efforts aim to develop closed-loop extraction systems that avoid sediment plumes and improve waste handling procedures offshore to prevent toxic discharge.
Eureka: A sustainable seabed mining robot
Impossible Metals has developed an innovative underwater mining robot prototype, Eureka, for sustainable, low-impact seabed resource extraction. Eureka boasts advanced artificial intelligence and a precision robotic arm that delicately plucks valuable nodules while minimizing disturbance to the marine ecosystem.
The prototype proved its capabilities during successful testing in Lake Huron, and advanced versions are planned to operate at depths of up to four miles. The company aims to mitigate sediment plumes and other mining impacts through its selective extraction process, offshore processing, and reduced waste.
Case Study: Japan successfully undertakes large-scale deep-sea mineral extraction
In 2017, Japan achieved a significant deep-water seabed mineral extraction off the coast of Okinawa, marking a notable milestone in this field.
This endeavor was initiated following discoveries of ore deposits off the Okinawa coast and involved deploying excavators to access the ore deposits at a depth of approximately 1600 meters.
The project tapped into zinc, gold, copper, and lead deposits, potentially reducing Japan's mineral imports and making it a resource-producing nation. This development highlights the importance of sustainable practices in deep-sea mining and their potential to reduce dependency on mineral imports.
Future Prospects of Deep-Sea Mining
Growing global demand for minerals like cobalt, nickel, and copper, driven by clean energy technologies, has led to the argument that deep-sea mining could provide a more sustainable solution than terrestrial mining.
The future sustainability of deep-sea mining will depend on industry innovation and the adoption of best practices, such as precision robotics, closed-loop extraction, and robust monitoring.
The ISA recently postponed the approval of deep-sea mining codes until 2024 due to environmental concerns, although there are some concerns that mining could still proceed through existing legal gaps.
This article has explored the viability of deep-sea mining as a sustainable alternative to land-based mining for essential metals. Supporters highlight its potential to access seabed minerals with fewer environmental impacts, but critics express concerns about unforeseen ecological consequences.
Nevertheless, technological challenges and regulatory issues remain. A cautious approach, guided by the precautionary principle, is recommended until comprehensive scientific assessments are conducted.
References and Further Reading
Blanchard, C., Harrould-Kolieb, E., Jones, E., & Taylor, M. L. (2023). The current status of deep-sea mining governance at the International Seabed Authority. Marine Policy, 147, 105396. https://doi.org/10.1016/j.marpol.2022.105396
Graham, J. (2023). ANALYSIS-Deep-sea mining: a new gold rush or environmental disaster? Available at: https://www.reuters.com/article/global-climate-change-mining-ocean-idINL8N38S52H
UK Parliament. Greenpeace UK submission to Foreign Affairs select committee’s critical minerals inquiry (MIN0051). Available at: https://committees.parliament.uk/writtenevidence/119401/pdf/
Impossible Metals. (2022). EUREKA! Impossible Metals reveals successful proof of concept for sustainable seabed mining of critical minerals. [Online]. Available at: https://impossiblemetals.com/blog/eureka-impossible-metals-reveals-successful-proof-of-concept-for-sustainable-seabed-mining-of-critical-minerals/
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. https://doi.org/10.1371/journal.pone.0171750
Levin, L. A., Amon, D. J., & Lily, H. (2020). Challenges to the sustainability of deep-seabed mining. Nature Sustainability, 3(10), 784-794. https://doi.org/10.1038/s41893-020-0558-x
Ma, W., Zhang, K., Du, Y., Liu, X., & Shen, Y. (2022). Status of Sustainability Development of Deep-Sea Mining Activities. Journal of Marine Science and Engineering, 10(10), 1508. https://doi.org/10.3390/jmse10101508
Muñoz-Royo, C., Peacock, T., Alford, M. H., Smith, J. A., Le Boyer, A., Kulkarni, C. S., ... & Ju, S. J. (2021). Extent of impact of deep-sea nodule mining midwater plumes is influenced by sediment loading, turbulence and thresholds. Communications Earth & Environment, 2(1), 148. https://doi.org/10.1038/s43247-021-00213-8
Owen, W. (2021). Subsea mining; technological and regulatory challenges. [Online]. Available at: https://www.globalminingreview.com/mining/25102021/subsea-mining-technological-and-regulatory-challenges/
Reuters. (2023). UN watchdog delays deep-sea mining to 2024. [Online]. Available at: https://www.reuters.com/markets/commodities/un-watchdog-delays-deep-sea-mining-2024-2023-07-25/
Sharma, R. (2011). Deep-sea mining: Economic, technical, technological, and environmental considerations for sustainable development. Marine Technology Society Journal, 45(5), 28-41. https://doi.org/10.4031/MTSJ.45.5.2
The Japan Times. (2017). Japan successfully undertakes large-scale deep-sea mineral extraction. [Online]. Available at: https://www.japantimes.co.jp/news/2017/09/26/national/japan-successfully-undertakes-large-scale-deep-sea-mineral-extraction/