Deep sea mining

Did you know that there is a treasure lying on the bottom of the oceans that is estimated to be worth as much as 385,3 billion US dollars, and it is still almost untouched?

It is made of precious metals and…no, it is not the treasure of an unlucky pirate ship that sank hundreds of years ago. 

We're talking about manganese nodules — rocks on the ocean floor that are full of valuable rare earth metals!

Deep sea mining, the practice of extracting minerals from the seabed. This is our toppic of today,  and this is quite a hot topic!

There is a lot of money involved, technical challenges and, of course, massive environmental issues. Quite an exploding mix!

This article is divided into 2 sections. First, we’ll define deep-sea mining more clearly and then discuss the environmental aspects involved..  

What is Deep-Sea Mining?

Deep sea mining refers to the mining of rare earths at the bottom of the oceans.

Long story short, the practice consists in  patrolling hundreds of square kilometers of ocean with a giant submarine vehicle that works like a giant vacuum cleaner: it inspires  tonnes of seabed sediments in the hope of finding manganese nodules, small round rock formations the size of a tennis ball. Once “mined”, these nodules are transported to the surface, where a ship washes and stores them. 

Who cares about manganese nodules, you may say!?!…

Well, manganese nodules are rich in rare earth and minerals that are used in a wide range of applications across various industries. These materials include manganese, nickel, cobalt, molybdenum, and more.  

Not all of the ocean seabed is covered in manganese nodules, but there are a few areas in which they concentrate, and they often peacefully lie right on the bottom of the seabed without having to dig deep.

It is estimated that the total value of these deposits is worth as much as 385,3 billion US dollars - an impressive figure, to say the least!  (Len et al., 2021). 

The sustainability aspect

Mining square kilometers of the deep sea isn’t the most sustainable  activity to the ocean, as it generates massive environmental issues.

There are mainly 3 environmental impacts The first is the scraping and sifting of the seabed, then there are consequences due to  the lifting of  seabed sediments, and third, there are impacts generated by the washing and the sifting of the nodules once they reach the surface and they are washed.

These activities do not only affect the seabed but also the whole water column between the deep-sea mining rover and the supporting surface ship. Indeed,

scraping the bottom of the ocean in search of minerals modifies square kilometers of marine sea bed affecting the life of all the creatures that live down there. 

The main result is that for collecting the nodules, large quantities of sand and seabed are lifted. 

To get a better idea, for every tonne of manganese nodules mined, between 2,5 - 5 tonnes of seabed sediments get  lifted (Sharma, 2015). 

According to estimates by Sharma (2015), extracting 1.5 to 3 million metric tonnes per year through deep-sea mining disturbs an area of 300 to 600 square kilometers annually.

The sediments remain suspended for a long time, making the water overall more cloudy, filtering therefore the amount of sunlight penetrating the water.

This has consequences  not only on the fish and fauna in the surrounding area, but also on the microorganisms that are in the water. 

At the seafloor level, the fauna gets depleted by the underwater nodule collector that smashes  it. We are talking about hundreds of square kilometers a year. On top of that, there’s also  the suffocation and entombment of living organisms  where the sediments settle. Benthic fauna, composed of tiny shrimp and other small organisms that live on the seafloor, is particularly affected by this, and as a consequence, all their predators and the food chain connected to them. 

All over the water column, the sediments left by deep sea mining affect the planktons as well as other fishes and fauna living in this zone. Particularly affected is  the plankton and all of the supply chain they sustain. On top of this, the copper, lead, and other toxic substances dispersed during the mining also pollute the water.

At the surface level, the materials that are reversed in the ocean decrease the amount of light penetrating through the water and affect the ecosystems lying below this. 

For more detailed information regarding the impact of deep seas mining, I refer you to the two articles in the references, in which every activity and its impact is described in greater detail. 

In conclusion…

Deep-sea mining is a very invasive technique to extract minerals from the bottom of the ocean. While it can surely bring economic value, it comes with extremely serious consequences for hundreds of square kilometers of ocean. 

In my opinion, I see the use of this practice as invasive toward the ecosystems and the deep sea, which often hides creatures that science still has to discover and that are unknown to us. This is made worse  by the fact that the elements extracted through deep-sea mining  can also be found by simply enhancing our commitment to the recycling of e-waste and the circular economy. 

Thinking of invading an ecosystem that is still so mysterious and unknown to humans reminds me of the movie Avatar, in which, in the race to economic profit, humans are willing to destroy whole new and unexplored ecosystems, without realizing that in seeking one treasure, they are destroying another one of far bigger size and value. 

So my question is, is manganese worth it? 

written by Riccardo Antoniolli, Green Office volunteer

References

Len, D., Shao, S., Xie, Y., Wang, H., & Liu, G. (2021). A brief review of recent progress on deep-sea mining vehicles. Ocean Engineering, 1 - 17.

Sharma, R. (2015). Environmental issues of deep sea mining. procedia Earth and Planetary Science, 204 - 211.