Podcast: Rich pickings on the abyssal plain?

Episode three of Mining the Deep by Sustainable Asia dissects the persuasive arguments for and against raking metallic rocks off the international seabed

Rich pickings on the abyssal plain?

While digging up hydrothermal vents is understandably controversial due to their rich biodiversity, there is another method of mining the seabed that may be less harmful. Four thousand metres under the Pacific ocean in the Clarion Clipperton Zone, the vast, flat seafloor known as the abyssal plain is littered with potato-sized lumps of rock rich in minerals.

Mining company DeepGreen is keen to start harvesting these “polymetallic nodules”. They argue that doing so will be far less destructive than mining practices elsewhere, especially on land where minerals are increasingly hard to reach.

But should we really be opening up a whole new area of exploitation before we’ve done everything we can to properly recycle the metals we already have? And what of land-based mines – what will happen to them once mining begins on the ocean floor?


  • Gerard Barron, Gregory Stone, DeepGreen
  • David Santillo, Greenpeace
  • Matthew Gianni, Duncan Currie, Deep Sea Conservation Coalition
  • Chong Chen, Japan Agency for Marine-Earth Science and Technology
  • Julia Sigwart, Queen's University, Belfast

More from this series


Podcast: Is the ocean floor worth sacrificing?

Episode one of Mining the Deep, a new podcast series by Sustainable Asia, explains what the drive to exploit the deep seabed will mean for this vulnerable environment

Podcast: The damaging failure of seabed mining in Papua New Guinea

Episode two of Mining the Deep by Sustainable Asia looks at the controversial Solwara 1 project and the downfall of mining company Nautilus

Podcast: Is the UN body in charge of our ocean floor capable of protecting it?

The fourth and last episode of Mining the Deep by Sustainable Asia asks if the world is really ready to start mining the deep seabed


Marcy Trent Long: Welcome to Mining the Deep, a podcast series by Sustainable Asia. My name is Marcy Trent Long.

In the previous two episodes, we looked at the growing need for minerals to build our renewable energy sources. We saw how deep-seabed mining might offer a solution, but we also learned about the risks of destroying unique habitats like hydrothermal vents and the financial burden these experimental ventures can have on developing nations.

In this episode, we’ll follow mining company DeepGreen out to the open ocean, more specifically to the Clarion Clipperton Zone.

International Seabed Authority (ISA) meeting: The Clarion Clipperton Zone, or the CCZed or the CCZee, depending upon your nationality… It’s probably the most studied area for these seabed deposits in the world.

Marcy: This is a recording from a 2009 meeting by the International Seabed Authority. They’re discussing an area of seabed the size of the United States, stretched out in the Pacific waters between Hawaii and Mexico.

ISA meeting: And it is in this area that most of the large deposits have been found over time.

Marcy: The mineral deposits in this area are concentrated in what’s known as “nodules”. Potato-sized lumps of black rock full of manganese, nickel and other minerals. They form over thousands of years, when mineral particles sink to the bottom of the ocean and accumulate around a hard object like a shark’s tooth. So if they’re just there, lying on the seafloor, maybe they could solve our demand for minerals.

Gerard Barron: It’s a resource made by Mother Nature that just happens to sit on the abyssal plain 4,000 metres below sea level, in one concentrated area.

Marcy: This is Gerard Barron. We’ve heard him in episode two as well. He’s the CEO of mining company DeepGreen.

Gerard: This is a very, very unique resource with enough nickel and cobalt, and manganese and copper, to electrify our entire transport fleet four times over. You know, it’s not full of gold, it’s not full of precious metals, it’s full of base metals that we need to build batteries.

Marcy: I also spoke with Dr Gregory Stone, the chief scientist at DeepGreen.

Gregory Stone: These base metals, the copper, the nickel, the cobalt, the manganese – the atomic properties of these metals… we can’t replace that. They’re really quite extraordinary. They’re like rubber bands that store energy and release it.

Marcy: Gregory and Gerard are clearly sold on the concept. And that’s understandable. If the world accepts deep-seabed mining, this could become a multi-billion dollar industry, with DeepGreen at the forefront.

NGOs like Deep Sea Mining Campaign are already suspicious of Gerard Barron, an early investor in Nautilus, who cashed out of the disastrous Papua New Guinea project before it fell apart.

So it’s worth trying to understand what these nodules really mean for our renewable energy future and what opponents of deep-seabed mining think. Here’s Dr David Santillo, the Greenpeace scientist we’ve heard previously.

David Santillo: I think that there’s a real danger in conflating the green revolution with a need inevitably to mine the seabed. It’s true that we’re using a lot more metals now, and quite a range of different metals, including those rare earths that we perhaps weren’t using anything like as extensively in the past; and that if we move towards an increasingly electronics-based economy in lots of countries, smart technologies, if we’re moving towards renewable energy, that the demands for some of those minerals are going to increase, at least in the short term. But the question is really: what can we do about the supplies of those? Are there not ways in which we can better recover those metals in obsolete products, and make sure that we’re building these devices, whether they’re solar panels, electronics for wind energy, for vehicle technology, can we not build them in ways in which we can actually close the loop much more effectively on recycling? Some of those minerals that we go to such lengths to get out from resources on land, they’re recycled at the moment less than 1%.

Marcy: That’s a good point. Do we even need to mine the seabed if we already have so much nickel and copper in the products we throw away every day?

Matthew Gianni: We need as a society to make much better use of the resources that we have.

Marcy: Matthew Gianni, from Deep Sea Conservation Coalition.

Matthew: And until we get up to a level where we’re recycling the kinds of metals that are found in the deep ocean in the products we’re using today… We shouldn’t be opening up a whole new area of resource exploitation, with unknown ecological consequences, before we start making better use of what we already have.

David: When people look into the future, they see minerals still as a non-renewable resource, of course, but also as a non-recyclable resource, almost as a single-use resource. And if we look at it in that way, then of course, you’re looking at something which is finite on land, and equally is going to be finite if we mine the seabed. So this is not a solution to an unending supply of minerals. In most cases, it’s just going to look to extend the supplies of these minerals by a few decades. But it doesn’t break us out of that same approach of unsustainable use, and perhaps, even greater unsustainable use in the future. And if we’ve got the ingenuity as a species to even consider going out and mining the seafloor, surely we can put that ingenuity to better use to protect the seabed and to make much better use, and much smarter use, of the minerals that we have already.

Marcy: I put that question to Gerard and Gregory of DeepGreen. Do they not agree that for a truly sustainable future, we need to work towards a circular economy?

Gerard: As an organisation, we’re big believers in the circular economy. The circular economy is all about moving towards more recycling. And I often hear people say: “Recycling should take the place, we shouldn’t need to mine anything new, we should just recycle.” Well, you know, that’s just, unfortunately, an uninformed position. Because to allow recycling, you need a bigger base load of metals. You need to be able to have more metals in the system, and then you need to encourage recycling.

Gregory: We do believe that in some number of years, it’s possible to acquire enough metal with a corresponding recycling strategy for those metals, that we should be able to close that loop. But we simply don’t have enough in circulation right now to do that.

Marcy: That’s true, take copper for instance. More than 80% of copper is currently recycled, but the demand for copper is so high that all the recycled copper amounts to just a third of what we need. So only when we have more copper in our production and recycling systems will we be able to close the loop. But, if we can close the loop in the near future, is it even worth it to start up a whole new extractive industry in the meantime?

Break to thank sponsors.

Marcy: In 2016, researchers at the University of Technology, Sydney looked at the quantity of minerals that is economically available to mine on land, and they concluded: “A transition towards a 100% renewable energy supply can take place without deep-seabed mining.” I put those results to Gregory.

Gregory: That’s true. But you have to think about where that metal is. All the high-grade ore sites, people go there first. And we’ve already started to move down, I’m told, to lower-grade terrestrial ores. And also nickel, some, or much, or a lot of that is found beneath tropical rainforest. So you want to think about where that metal is going to come from that is in the ground. But yes, if you want to just keep digging, and going for the terrestrial deposits, you can keep doing that. That’s true.

Marcy: So, if we want to get enough base materials in the system to achieve a circular economy, it’s not really a question of whether we need to be mining the seabed, but whether we prefer it over mining on land. And this is the key argument. You’ll hear it from everyone who supports deep-seabed mining: it’s the best option.

Gerard: The challenge when you getting a new industry going is: how do you benchmark what you’re doing versus what the known alternatives are? And the known alternatives, of course, are what’s happening on land. And that’s there for all of us to see. And so the question when we’re trying to build the case for ocean nodules is: is it better? The fact is, we don’t have to do any of the things that are normally associated with land-based mining. We don’t have to blast and drill and create nasty tailings ponds.

Marcy: Tailings, by the way, is what’s left over after the minerals have been separated from the ore. In land-based mining, they’re usually toxic lakes of cyanide or other acids.

Gerard: You can understand why people are anxious. You know, when you wake up in the morning and you realise there’s been a tailings dam spill in Papua New Guinea, or villages have been wiped out in Brazil due to tailings collapse. You know, people are suspicious of the mining industry.

Gregory: You don’t have that with this. You don’t have tailings. You have these rocks that you pick up, and you process them. I see it as the most earth-friendly way to get these metals.

Marcy: So it’s completely harmless then, right? I know we’re not tearing down hydrothermal vents here, like the Lost City or the ones with the scaly-foot snail. These are just nodules, rocks with a bunch of minerals in them, that we can scoop up…

Matthew: They’re basically finding that what heretofore had been considered, or thought of, as a very large area of deep abyssal plain that consisted of rocks and mud and these so-called polymetallic nodules with metals such as cobalt, nickel, magnesium and copper in them, are actually ecosystems of relatively high biodiversity.

Marcy: So animals live on and among these nodules? To find out more, I asked Chong Chen, the deep-sea biologist who studies the scaly-foot snail.

Chong Chen: So we have new species of sponges and also molluscs. There are these very rare molluscs called monoplacophorans that love the nodules, and they will basically occur only on the nodules. Many species have only ever been found on the nodules. And then you have small species of… So, they’re not big. They’re not big animals like the hydrothermal vent ones, because there’s no energy production. But you have many, many small species like worms, snails, limpets and sponges, that live on these nodules and nowhere else.

Marcy: So whereas in hydrothermal vents you get large species like crabs and sea worms all grouped together around the vent system…

Julia Sigwart: Habitats like nodule fields are much more widespread.

Marcy: That’s Julia Sigwart, Chong’s research partner.

Julia: They’re much more difficult to study, in terms of the biodiversity, what’s there, how abundant the animals are, what the ranges of the species that live there [are]… We actually know much less about the biodiversity in nodule fields. That doesn’t mean the biodiversity isn’t there and isn’t valuable, it just means that it’s spread out over a bigger area.

Marcy: And even though the animals that live there are so spread out, the nodule mining still poses a high risk to their survival because of the scale of this activity.

Matthew: If you put a mining operation into one of these areas, and the mining occurs at the level [of] the target production levels established by the ISA, the International Seabed Authority, which is roughly three million tonnes of nodules per year… A typical mining operation over the course of a 25 to 30-year contract would directly impact somewhere between 8 and 10 thousand square kilometres of ocean bottom, and have a knock-on impact of another 10 or several tens of thousands of ocean bottom.

Marcy: But Gerard of DeepGreen says we’re looking at this all wrong. When asking the question: “What’s better, mining on land or in the ocean?”…

Gerard: You can’t look at that question and answer by looking at one simple area. And so we decided that it was necessary to do a full lifecycle analysis, from cradle to gate, looking at a multitude of areas.

Marcy: So what Gerard and his team did was to look at seven areas of potential damage. Things like biodiversity loss, but also the amount of carbon it would release. They compared the results for both mining methods, and found that, on the whole, land-based mining would be worse than seabed mining.

Gerard: There’s a lot of assumptions that people, especially NGO people, like to jump to. And that’s because they don’t look at these seven areas, they look at their area. And, you know, as responsible citizens of the planet, I think you can’t afford to do that. You have to look at this from a complete ecosystem perspective.

Marcy: But there’s one key problem with this: right now, we already have land-based mining. So is that just going to stop when we start mining the ocean?

Duncan Currie: It’s not simply a question of: do you take the minerals from land or from sea?

Marcy: Duncan Currie, an environmental lawyer with Deep Sea Conservation Coalition.

Duncan: Because the reality is, if you have seabed mining, you’re going to be almost certainly using both. Minerals are going to continue to be produced from land as well as from the deep ocean. And therefore, the question arises: are you not opening up a whole new area of environmental damage by starting seabed mining?

Marcy: Matthew Gianni agrees.

Matthew: There’s no guarantee that even if you were to mine, say cobalt, in the deep ocean, that the worst of the terrestrial mining operations would shut down as a result. To the contrary, they may even get worse, in the sense that terrestrial mining operations that are trying to improve their human rights and labour standards, trying to improve their environmental performance, might end up cutting back on investments in these sorts of things if they had to compete with cheaper metals coming out of the deep oceans. You know, they might decide to cut costs and ignore, or otherwise work to limit or reduce, environmental regulations and rules, or child labour standards, or whatever.

Marcy: This sounds like something that really needs to be worked out first. Surely we cannot allow seabed mining to start if we know it will make land-based mining even worse.

But we have a chance to do this right. Right now at the International Seabed Authority, member states are negotiating a set of rules for seabed mining. It’s called the Mining Code, and it even includes provisions on compensating countries that depend on land-based mining. We might do something properly this time, right? Well… scientists and environmental groups are very, very concerned about the way the International Seabed Authority works.

Matthew: There’s a growing recognition that the world isn’t ready to start doing this, and a real worry that the ISA, because of its bylaws and the structure and the decision-making process that’s in play at the moment, will drag the world into deep-seabed mining without the full consent of the international community as a whole, or the ability for all of us to collectively decide whether this is a good idea or not, and how much more information we need before we can make informed decisions.

Marcy: In the last episode of Mining the Deep: what’s going on at the International Seabed Authority, and do we have a chance to set things straight before large-scale seabed mining really takes off?

Mining the Deep is hosted by me, Marcy Trent Long, and produced by Samuel Colombie, in collaboration with China Dialogue. The series is mixed by Chris Wood.

Thanks to all our guests for helping us unravel this complicated issue, to Miguel Urmeneta for his voice-over, and Alexander Mauboussin for his intro music, made from repurposed and recovered waste items. Additional thanks to the podcast “After the Fact” by Pew Charitable Trusts, for providing audio from a speech by Michael Lodge. Thank you to the entire Sustainable Asia team, Bonnie and Heidi Au, Josie Chan, Crystal Wu and Jill Baxter.

Production credits:

Executive producer and host: Marcy Trent Long
Producer: Samuel Colombie
Sound engineer: Chris Wood
Intro/outro music: Alex Mauboussin