This article is part of our series on responsible mining solutions. The push for clean energy is fueled by a growing demand for minerals, but conventional mining has a track record of harmful social and environmental impacts. Experts are exploring whether deep-sea mining could be a solution to that problem.
The demand for clean energy minerals attracted attention to the ocean floor, where lie millions of potato-sized rocks rich in manganese, cobalt, copper and nickel. Packed inside these nodules are greater quantities of minerals than all land reserves combined.
Currently, no commercial deep-sea mining projects exist anywhere in the world, but around 20 companies are licensed to “explore” the deep sea. The path to green-lighting commercial mining is still under construction. The major roadblock is the uncertainty of the environmental impacts.
Companies that want to mine the deep sea argue that research shows severe negative impacts are unlikely. Environmental organizations say we still need 10 to 25 years of research to truly understand the potential impacts. The organization in charge, the International Seabed Authority, says it is carefully developing commercial mining regulations, implementing a precautionary approach.
“To act responsibly, you need to know what the likely outcomes of your actions are, and I don’t think we really understand that yet,” said Oliver Ashford, a senior associate of the World Resources Institute’s Ocean Program. “It would be a bit of a step into the dark.”
What are the potential impacts of deep-sea mining?
Polymetallic nodules sitting on the deep ocean floor, around 2.5 to 3.5 miles deep, are actually pretty accessible. No digging, blasting, tree felling, or community displacement is necessary. Mining companies send a machine down there, and it picks up the rocks and brings them back to the surface.
The process isn’t harmless, though. Many companies propose using a sort of bus-sized Roomba to crawl the ocean floor and suck up the nodules. Immobile life in its path will perish, and sediment plumes kicked up by the machine will cloud the area for some time before settling, perhaps impacting organisms’ ability to breathe and sense their surroundings. Microbial communities, which make up the majority of life in the deep ocean, will also be heavily impacted in the areas where the machines operate.
Larger organisms like corals and sponges are known to anchor themselves to the nodules, which provide a firm surface along the ocean floor. A deep-sea octopus species was observed laying its eggs on a sponge anchored to a nodule. Relative to other ecosystems, life is sparse in the deep ocean, but animals will undoubtedly be impacted by deep-sea mining.
One company, Impossible Metals, is developing a more targeted machine that hovers above the sea floor and, using artificial intelligence, selects nodules that have no visible life on or near them.
Still, other impacts are not fully known. Questions arise over the effects of noise and light disturbances in the deep ocean and how mining may impact the ocean’s natural carbon cycling and sequestration. One study suggested the nodules may be creating oxygen via hydrolysis, but those findings are hotly contested.
Many organizations and countries say we don’t have enough data on the deep ocean and the potential impacts of mining it. They want a minimum 10-year moratorium on any commercial mining permits until enough data is collected.
Mining companies say the early data shows that detrimental impacts are not likely. Some propose an adaptive management system where, as mining starts and impacts are measured, regulations can be adapted to ensure impacts are minimized, and if necessary, stop the mining.
“If you realize that an impact is more adverse than you previously anticipated, you could tell them to stop, and the impact ceases,” said Seaver Wang, director of climate and energy at the Breakthrough Institute, a global research center for environmental and human development challenges. This is different from land-based mining, where the environmental impacts of clearing land, removing the overburden, and blasting the pit open have already happened before a company starts collecting metals.
The deep sea is fragile and unknown
The deep sea is a cold, dark place with scarce food sources. A place where life is not used to change. “Probably the biggest natural disturbances that you would get there would be things like whale falls and other large creatures in the water column dying,” Ashford said. “That would be quite a different circumstance from having a mining vehicle going over the seabed.”
Testing deep-sea mining vehicles goes back to the 1970s, when a prospective company sent its vehicle to the seafloor to collect nodules off the coast of Georgia in the Atlantic Ocean. While it failed to prove economic feasibility, the machine left tracks on the ocean floor that are still visible today.
“The fact that the test site remains barren compared to surrounding areas is hard physical evidence of how long-lasting deep-sea mining damage might be, and we still know so little about how these ecosystems respond,” said Jillian Acker, research associate at the ocean conservation organization Oceana.
Is deep-sea mining more harmful than land-based mining?
To date, around 90 percent of deep-sea species are still undescribed by science. Understanding the impacts of deep-sea mining on those species is difficult, given that we don’t know much about them.
“I do think it’s a valid concern, but I think there’s a bit of a misconception,” Wang said. “Frankly, there are a fair amount of microscopic land organisms that are also uncharacterized.”
To Wang’s point, studies vary, but most conclude that around 85 percent of land-based species are undescribed.
Saying that minerals 15,000 feet below the ocean surface are easy to access is an oversimplification, but it’s arguably less impactful to go through miles of water than miles of rock on land.
Land-based mining has caused horrifying environmental impacts. The Vale tailings dam failure in Brazil in 2019 killed 270 people and spilled 12 million cubic meters of toxic mine waste, damaging the surrounding environment and water systems. The Mount Polley tailings disaster in Canada in 2014 released 25 million cubic meters of tailings into Polley Lake and surrounding waterways.
Some land-based mines have even pumped their tailings into the ocean on purpose to avoid tailings dam failures. Other land-based mining impacts include deforestation, water and soil contamination by toxic elements, erosion, and a whole bevy of human and social impacts.
In contrast, deep-sea miners claim zero-waste mining is possible, given the high metal content of the nodules and the non-toxic elements left over that can be processed for fertilizer and construction aggregate.
With massive quantities of metals sitting on the ocean floor, and land-based mining continuing to impact communities and environments, deep-sea mining could provide some positive benefits if it is managed and regulated responsibly.
“The technological ceiling for seafloor nodule collection in terms of impacts mitigation is still very high because this industry is in its nascency,” Wang said. “Environmental groups should be more open-minded to seafloor mineral collection because with the progression of technology, we ought to be able to keep further reducing those impacts.”
