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Podcast: The ocean floor is littered with valuable minerals. Should we go get them?

C&EN reporter Priyanka Runwal dives into the controversy around deep-sea mining in international waters

by Craig Bettenhausen , Brian Gutierrez, special to C&EN
December 11, 2023


An organism with many white, whispy arms protruding from its center hovers above the ocean floor. It is attached to a dead sponge stalk on a nodule.
Credit: Diva Amon/Craig Smith/University of Hawaii
Credit: C&EN

Resting on the bottom of the ocean are potato-sized nodules of valuable minerals that are more or less up for grabs. Multiple corporations and some nations are racing to build deep-sea drones that can withstand the extreme conditions at the seafloor and bring these 1–20 cm nodules to eager buyers on the surface.

Many of the metals in these nodules are critical for green technologies like batteries. But these nodules are also an important part of ecosystems we are just beginning to understand. In this episode, C&EN reporter Priyanka Runwal chats with host Craig Bettenhausen about this complex issue.

C&EN Uncovered, a project from C&EN’s podcast,Stereo Chemistry, offers a deeper look at subjects from recent stories. Check out Runwal’s full story at

Subscribe toStereo Chemistry now on Apple Podcasts, Spotify, or wherever you listen to podcasts.


Executive producer: Gina Vitale

Host: Craig Bettenhausen

Reporter: Priyanka Runwal

Audio editor: Brian Gutierrez

Copyeditor: Bran Vickers

Story editor: Laura Howes

Episode artwork: Diva Amon/Craig Smith/University of Hawaii Music: “Hot Chocolate,” by Aves

Contact Stereo Chemistry: Contact us on social media at @cenmag or email

The following is a transcript of the episode. Interviews have been edited for length and clarity.

Craig Bettenhausen: Welcome to C&EN Uncovered. I’m Craig Bettenhausen. C&EN Uncovered is a podcast series fromStereo Chemistry. In each episode, we’ll take another look at a recent cover story inChemical & Engineering News and hear from C&EN reporters about striking moments from their reporting, their biggest takeaways, and what got left on the cutting-room floor. In this episode, we’re talking about a recent cover story about mining the ocean floor, which appeared in the Oct. 9th issue of C&EN. We’ll put a link in the show notes. I’m here with C&EN physical sciences reporter Priyanka Runwal, who wrote that article. Hi, Priyanka.

Priyanka Runwal: Hey, Craig. Thanks for having me.

Craig: So for folks that haven’t yet had a chance to read the article, can you give a brief summary of what’s in the story?

Priyanka: For sure. So the story’s about important minerals found in the deep ocean, whose existence we’ve known about. But in the last few decades, these reserves have attracted significant mining interest. Some of the minerals that I’m referring to include nickel, cobalt, copper that are vital for clean energy technologies such as electric vehicle batteries, wind turbines, solar panels.

Craig: So how did you go about reporting this? I mean, I’m guessing you didn’t get to, you know, do a ride along on one of these barges.

Priyanka: Oh, I wish I could have. But one of the people who I first called was a marine geologist named Jim Hein. I really wanted to know from him how the deep-sea minerals form, what they look like, how these minerals are retrieved. He told me that there are basically three kinds of deposits. [It’s] one of them, nodules, which are these dark-colored, almost potato-sized rocks strewn on the ocean floor, which are of most mining interest.

Craig: Can you describe a little more about how these nodules form?

Priyanka: Yeah, so think of a small object like a dead shark’s tooth or the remains of a shell lying on the seabed. Minerals such as manganese and iron that are dissolved in the seawater precipitate onto these objects, and they accumulate layer by layer and bind other important dissolved minerals. These could include nickel, cobalt, copper, and it takes millions of years for these nodules to form. There’s an area called the Clarion-Clipperton Zone in the Pacific Ocean where nodules are most abundant, and there’s a lot of mining interest currently in that particular area. And where a lot of these test mining operations have also happened.

Craig: How did they find these things?

Priyanka: So this was almost 150 years ago, when scientists and sailors set sail to explore the world’s oceans. And the way they were doing that is they would dredge parts of the seafloor and pull up the dredge, and in one of these dredge pulls they found these—as the scientists on board the HMS Challenger described it—“peculiar rocks,” which were black, bumpy, fairly lightweight for a rock that size. And these were among the first nodules to be recovered from the deep sea.

Craig: When they found these things, did they know that they’d found something interesting and valuable? Or was it just sort of like, “Oh, look at this weird rock”?

Priyanka: I mean, they knew that the rocks had important minerals. Did they know that they were going to be commercially important someday? Probably not. I knew they thought these rocks were important because I think they found, like, fossil remains in these rocks. So they thought they might be important for, you know, that purpose, but not necessarily, you know, commercially important.

Craig: How deep is the deep sea that we’re talking about here? I mean, it’s ocean floor, but how far down?

Priyanka: Sure. I mean, for nodules, it’s about 4,000 m, you know, deep into the ocean, which is, like, really, really deep.

Craig: Is this, you know, beyond the range of human exploration? Like, would we just be crushed instantly if we went down there ourselves?

Priyanka: It’s not necessarily, like, areas of depth that people are, are, you know, going down and exploring. So yeah, the deep sea is this very sort of unknown environment with a lot of creatures lying down there that we know very little about. It’s so dark out there that a lot of these remotely operated vehicles have to carry huge lights to illuminate these parts of the deep sea.

Craig: So in your story, you had some cool photos that I assume are from the mining ships. Could you describe that a little bit? Like, obviously you can’t see down there ’cause there’s not human light, but if you were able to, what would it look like?

Priyanka: Oh, it would be this very, very eerie, dark space that’s suddenly lit up by all of this lighting equipment that these ships and these remotely operated vehicles carry. When I looked at some of the photos of the nodules on the seafloor, it’s basically like lots and lots of these tiny, black-colored potato-like objects all across the seafloor, and it really looked very cool.

Craig: It’s probably unknowable, but I wonder if, for the creatures that are down there, if that light is scary or if it’s just so far out of their experience that it’s orthogonal to them. I don’t know.

Priyanka: I mean, one of the concerns from deep-sea mining is definitely light pollution. You know, researchers expect that the lights and sounds that deep-sea mining would create would also potentially be problematic for some of the creatures that live down there.

Craig: And so how are they controlling them? That’s a long distance through a medium that, you know, doesn’t always transmit well. I mean, is it like a giant RC [remote-controlled] car? Or how are they even controlled, these things?

Priyanka: Basically, there are school bus–sized remotely operated vehicles that are tethered to a mining ship that’s sitting on the sea surface, but essentially it’s a tether. It’s a wire that sort of takes them down to the deep sea, and there’s somebody up in the ship that’s controlling the vehicle. And these vehicles are sent down. They use seawater to create high-pressure water jets that stir up the seafloor mud and then dislodge the nodules, which are then vacuumed up.

In the process of creating some of these high-pressure water jets and stirring up the seafloor is creating these things called sediment plumes, where you have the mud that stirred up that eventually will settle down on the ocean floor, and that in itself creates a lot of disturbance for several animals and creatures that live on the deep sea that are sort of filter feeders. Basically, the sediments settling down on them would suffocate them.

Craig: Is it like a lush biota down there? What does the life look like at that depth?

Priyanka: I mean, I wouldn’t say it’s necessarily lush, but these are very high-pressure environments with very few nutrients available. So there’s very unique biodiversity that lives there. Among the species that might be affected by deep-sea mining particularly are these sponges.

Basically, these sponges are sessile. They sort of adhere to nodules, and when you take away the nodules, these sponges have nowhere to sort of anchor themselves. You’re essentially losing species like the sponges and several other species that depend on them.

Craig: Who else is down there? What are we talking about as far as the creatures?

Priyanka: Oh, there are several kinds of creatures out there. We’re talking about certain kinds of sea stars. We’re talking about a lot of small worms that use these deep-sea habitats.

Craig: So one thing you mentioned is that these nodules have been there for a long time. We’ve known about them for, like, 150 years. So why explore it now? And what industries are bankrolling this idea?

Priyanka: It’s really interesting, you know, in terms of “why explore now?” I asked this to several scientists as well. One of them told me that some of the key minerals that we need tend to come from China. We depend on China for a lot of these key elements such as nickel and lithium and several others.

And so, to diversify, countries had been looking for several other options, any which way. And especially the Metals Company, which is a Canadian company, had had a fair bit of investment money flowing in. And they’re really at the forefront of pushing the mining and the deep-sea agenda forward.

Craig: Is this something, you know, long term for electrification that we need to do, or is this a, you know, “somebody could make some money off of it” sort of a situation?

Priyanka: Certain companies have had a lot of money invested in making this happen for them. Why do we need it? Of course, there’s a growing demand to move away from the fossil fuels and to use more green and clean energy. Well, green and clean energy, it’s not just going to come out of nowhere.

We do need certain elements to make that technology happen and to sustain it. And where is it that we’re going to get some of these minerals from? That’s really at the heart of all of this.

Now, extracting these minerals on land typically requires slashing large areas of tropical forests and creating open pits to dig out the ore. There are obviously environmental problems to doing this but also issues of human rights violations, such as uses of child labor in Congo’s cobalt mines. Now, proponents of the deep-sea mining industry have basically argued that retrieving minerals from the seabed will be less environmentally damaging and socially damaging, but a lot of scientists I spoke with told me that it’s very unlikely that deep-sea mining will replace or reduce mining on land.

Craig: Do we have a sense of if this is more expensive or less expensive than terrestrial mining for some of the same materials?

Priyanka: I mean, for now, the estimates that I’ve seen suggest that deep-sea mining is going to be a lot more expensive than land-based mining. And, you know, it’s not just extracting, but there will be regulations in place where companies will be asked to restore some of these sites that they mine commercially. And restoring these habitats is going to be no easy task, and that’s going to be pretty expensive as well. So I’m guessing all together the cost of getting there, extracting these minerals, and restoring some of the disturbed sites is going to be pretty high.

Craig: Do we even, like, as a species have techniques for restoring things down that far?


Priyanka: I’m sure there are ways to do it. I’m just not sure if we really do know how. And really what it takes. And how long it’ll take for these sites to really be quote, unquote, restored. Because, you know, on land restoration, we know that it takes a long time for habitats to go back to the way they are. If at all they do.

We need a lot more long-term experiments to really know how this is going to impact things in the deep sea and whether it’s even possible to restore it. That’s really a huge open question.

Craig: Yeah, I was struck in your article in that section because even some of the microbial life in some of the studies had not recovered after 40 years. And usually you’d hope those are the first to return, and they just mostly hadn’t.

Priyanka: Yeah, exactly. That was surprising to me as well when I read one of the studies. It does take time for things to come back, for the nutrition levels to build to the levels that they were in the past.

So in a way, I’m not surprised that that microbial life has still not come back in the form that it used to be. One of the things that the scientists have really stressed on is doing more longer- term studies to really see what will be the impact and what’s going to come back and what’s just absolutely not going to.

Also remember the deep sea stores a lot of the carbon that’s not going into the atmosphere and not contributing to the climate change. We’re disturbing some of those dynamics down in the deep sea as well.

Craig: So also kind of probing on the kind of “Is it worth it?,” which I think is kind of the overall question that you’re asking here, let’s say we did go ahead with this. How much is down there? If we harvested all of it, how long would that supply last us?

Priyanka: From what I understand, I don’t think we need to even harvest all of it. A small portion of these abundant resources down there can really meet a large portion of our needs. So we won’t necessarily need a very huge part of the ocean that we would have to exploit. The portion that we will, will still create some sort of a significant impact. Is it worth it? I don’t know that we know.

Now, so far, the ISA has issued about 31 exploratory mining permits where companies could test run the operation and researchers could measure the impacts.

Craig: This group comes up a couple of times in your story, the International Seabed Authority.

Priyanka: Mm-hmm.

Craig: Who’s in charge of the sea? Who’s actually giving these people the authority to make these rules?

Priyanka: They’re UN [United Nations] affiliated. It’s 168 countries [and the European Union] that have representatives that are part of the International Seabed Authority that negotiate terms. However, in July, negotiations to finalize these regulations ended without any agreement.

Craig: So thinking about kind of the flow of money here, in modern-day surface mining, somebody owns that mine, that hill, that quarry; either it’s privately owned or it’s government land that’s being leased. Who owns the minerals on the seafloor? Or is it just up for grabs like your old-timey, you know, gold rush era.

Priyanka: It’s a little bit like that. It is nobody’s, and it is everybody’s. There are still issues about how certain countries who are wealthier will be able to access these deep-sea minerals. Other countries who don’t have that kind of money but still have a stake because it is still like international waters, how will they be compensated for not having the means to be able to exploit some of these resources?

So the benefit sharing is something that is still being figured out. How to make it equitable is also a huge open question at the moment.

Craig: So this is a big story with a lot of different angles. Is there anything that didn’t make it into the story that you found as you were reporting?

Priyanka: Yeah. I mean, one thing that I did not talk about—because a lot of my focus was on looking at what’s happening in the international waters—certain countries like Norway are also looking at waters that they have access to around their own land—water that’s governed by Norway; it’s within their territory—and they’re looking to start mining in the sea around them. So essentially, they would be doing the same thing, going down to the deep sea looking for these mineral deposits and extracting them.

Craig: So after doing all this reporting, I want to ask you to step outside your reporter comfort zone for a second. And where do you fall in the debate? What do you think ought to happen here?

Priyanka: I’m somebody who will take a cautious approach. Based on what we know, it seems that the impacts will be fairly long term, long lasting, potentially irreversible.

So many of these creatures depend on these nodules or are attached to these nodules. If you take those away and it takes millions of years to form, there’s a very small chance that in our own lifetime we’ll see these ecosystems sort of return to the way they were. So I feel exercising a cautious approach would be ideal. But on the other hand, I also know how extracting these minerals on land has so many problems of its own.

Craig: Well, Priyanka, this is a really interesting story to read, and I’ve really enjoyed our conversation. Thank you for diving deep with us on this.

Priyanka: Thank you so much for having me.

Craig: So you can find me on social media at CraigOfWaffles. How can people find you?

Priyanka: Oh, they can find me on Twitter [now known as X], and my Twitter handle is Priyanka_Runwal, P-r-i-y-a-n-k-a underscore R-u-n-w-a-l.

Craig: So you can find Priyanka’s cover story about seabed mining on C&EN’s website or in the Oct. 9th issue of C&EN. We put a link in the show notes along with the episode credits.

We’d love to know what you think of C&EN Uncovered. You can share your feedback with us by emailing This has been C&EN Uncovered, a series from Stereo Chemistry. Stereo Chemistry is the official podcast of Chemical & Engineering News. Chemical & Engineering News is an independent news outlet published by the American Chemical Society.

Thanks for listening.


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