Deep underwater, 4 km down, beyond the reach of our star’s light,
lie these dark potato-shaped nodules. They have been there for millions of years,
slowly growing in size, and these oddly shaped bulbs may hold the key to an electric future.
We have known about these formations for over 150 years. In 1873, HMS Challenger even managed to
collect samples from the mysterious abyss of the midnight zone. Dropping kilometre-long hemp ropes
with a collecting apparatus attached and by chance pulling one of these nodules to the surface.
Each of these lumps contain metals that can help solves one of modern
day’s greatest supply chain issues. Battery production. Containing manganese, cobalt,
nickel and copper , and they are scattered all over the vast seafloor.
It is estimated that a patch of land just over the size of Ireland
can yield over 54 million tons of metals, collectively worth over 20 billion dollars.
Since their discovery, they have served as no more than interesting
seafloor features. Given that the precious metal they contain can be mined on land,
there has been no incentive to profit off mining the nodules.
But, with growing supply chain woes, and growing competition in the electric vehicle
market, dozens of companies now seek new innovative ways to surface these nodules.
We know frighteningly little about the deep sea floor.
As you descend past 1000 meters, all light disappears, and thus, so does
all photosynthesis. The only light that may be visible is the faint twinkling of bioluminescence.
Without sunlight, food becomes extremely scarce, and animals rely on what is called
marine snow - the falling debris of organic material from shallower waters.
Because of these extreme conditions, the creatures in deep water have evolved to be
some of the most unique in the animal kingdom. At 4000 meters, you may find a semi-translucent
dumbo octopus scuttling along, or a gulper eel with its massive expandable gullet,
or a viperfish with its terrifying dead eyes and unbelievably sharp teeth. Deeper still, scavengers
and detrivores scramble across the bottom, looking for any morsel of food they can find. Animals like
this have been found as deep as 11,000 meters - at the bottom of the deepest parts of ocean.
ROVs and some manned missions are beginning to scratch the surface
exploring the depths of the sea, but it is no easy feat. Only 4 crewed missions
have ever been to the bottom of the Mariana Trench. The deep sea being
one of the last ecosystems on this Earth that has been largely untouched by humans.
This raises major concerns for the impact any mining operation will
have on the strange and wonderful life residing among these metal-rich deposits.
Early investigations of the seafloor in the 1960s and 70s revealed that the nodules are
clustered in certain areas of the sea floor. Their locations depend highly on environmental factors.
Needing high oxygenation levels and a source of metal in the seawater, or seabed to grow.
Similar to how the iron in steel reacts with oxygen and water to create a layer of rust,
nodules are formed in layers of oxidized metal.
For a nodule to form, a piece of debris has to sink into the
oxygen-rich environment of the deep-sea floor.
From above, free-flowing iron and manganese ions dissolved in water react with the oxygen
and form layers. These form nodules at the surface of the sea floor. [2]
From below, the metals get “pushed up” by concentration gradients through the
porous sediment, and once they reach the oxygen-rich environments they react and
start forming nodules 10 to 15 cm below the surface. Depending on their depth,
different percentages of metal will be present.
While the majority of the metals in the nodules are manganese and iron. Surface nodules are
exposed to more cobalt while the deeper nodules collect more lithium and nickel[2]
These layers form at astonishingly low rates around 1 to 10 mm per million years. [2]
In the time it took for our ancestors to spread out from Africa and dominate the world,
these nodules only grew the width of a human hair (.017- .18)mm. [3]
Scientists can predict where these nodules would appear based on these
environmental effects, and we have confirmed with
that they appear in high concentrations in the pacific and indian oceans.
[4] Most of these zones fall under international waters.
So, the UN set up the International Seabed Authority in 1994. Based out of Kingston,
Jamaica, to organize and control all mineral-related activities related to the seabed.
Up to now, they have not granted any licenses for mining operations but they have granted
permission to a total of 19 exploratory missions of these polymetallic nodules.
Of which 16 are based in the Clarion-Clipperton Zone (CCZ),
an area just off the coast of Mexico. [5] Each of these missions covers an area of around
75,000 sq km, approximately 0.16% of the area of the CCZ [6]
Estimations for the potential yield of a mine site this large are expected to
be about 1.5 Million tons of wet nodules per year.
A typical electric car battery has 35 kg of nickel, 20 kg of manganese,
and 14 kg of cobalt. [7] A mine this large would provide enough nickel for 400.000
car batteries (16,000,000/35), enough manganese
for 18 million (360,000,000/20 ), and enough cobalt (1,500,000/15) 100,000 cars per year [1]
The value of these deposits is undeniable, but we have never extracted solid minerals at scale
from the seafloor before. This is going to require new technologies, and unsurprisingly many borrow
from the oil and gas industry who are all too familiar with extracting value from the deep sea.
Companies first have to locate a region where the density of these nodules is
large enough to make extraction worthwhile. Autonomous submarines are first sent down
to access the area. Using pulses of sound to scan and map the seafloor.
The resolution of these scanners is too low to directly detect individual nodules,
which are usually about 10 centimetres in size, but they can estimate the density of the nodules
on the sea floor, before sending another expedition to collect physical samples. [8]
Now comes the difficult part. Extraction. Many different solutions have been proposed,
and there are several problems to overcome.
Some trials were conducted in the 1970s and 80s,
and the knowledge gained in these trials all led to the same proposals for a mining method. [9]
A self propelled rover would be lowered to the seafloor,
attached to a surface ship through a rigid riser and a flexible pipe.
These risers are technologies created by the oil and gas industry and are well developed.
Once the collecting rover touches down on the seafloor it can move around,
remotely operated from above.
The rover effectively acts like a potato harvester,
but instead of combing through the soil, most rovers will use a water jet to dislodge the
nodules and push them into the collector. We now need a way to transport the material
to the surface, and this is where most of the technological issues are found. [10]
Once the nodules are dislodged, the collectors carry the sludge
and the nodules through a separator. The unwanted liquid gets expelled
behind the collector causing a plume of dirt to trail behind the rover.
The leftover slurry with debris and nodules are now pumped up. Things get a little difficult here.
Raising material over a distance this large requires a great deal of energy.
However, attaching some kind of rope to raise material isn’t easily scaled.
Pumping liquid oil is vastly easier than transporting solid materials. Currently,
two main mechanisms have been proposed to bring the nodules up to the surface. [9]
One way is to pump compressed air into the pipe, which creates the necessary
pressure underneath the raw material to lift it to the surface. However,
this method has a very low energy efficiency, at around 15%. The second option is to space
out submersible centrifugal pumps along the rigid rise; this is currently the preferred method. [11]
Once at the surface the nodules are separated from the leftover
slurry. They are then dried out for transport to the mainland. However,
the unwanted slurry that is left over needs to be piped down and expelled into the water column.
This slurry is one of the primary environmental concerns of deep sea mining operations. [12]
Releasing at the top of the water column, where it can affect multiple levels of the
ocean ecosystem is not an option. At the very least, we need to pump the sediment down beyond
the photic and disphotic zones, these are the layers of the ocean that sunlight can reach.
Pumping sun-blocking sediment above these layers
would interfere with plankton and other photosynthetic organisms.
An MIT study, published last year, investigated the dynamics of this
sedimentation for both midwater dispersal and for sediment dispersed by the harvesting
rovers. They found their models lined up closely with in field experiments,
where they released sediment in exactly the same way off the coast of california. [13]
They found, thanks to rapid dilution in the sea currents,
that the sedimentation rate on the seafloor was drastically lower than
normal background sedimentation,and thus should not interfere with filter feeders in the region.
There was also no evidence of toxic elements in this extracted sediment. While it’s tempting to
compare this sediment to the toxic tailing pools we see in traditional ore extraction,
these toxic waters are a byproduct of the ore processing, this part of the process does not
happen at sea. This is simply surface sediment being returned to the sea.
However, even if the plumes of waste product have minimal impact, the mining
operations have the potential to wipe out species we haven’t even begun to study.
Sea sponges use the nodules as anchor points. Deep
sea octopus use them to lay and protect their eggs. [2]
And with these nodules taking millions of years to form, any surviving members of the species
that depend on them would be left without a home. Devastating an entire ecosystem,
which we have very little knowledge about, or its impact on the rest of the water column ecosystem.
One of the few studies on the impact of these operations was conducted in the late 80’s
by a German government-funded research expedition off the coast of Peru. [14]
To assess the effects of nodule collection, they carved out trenches and removed nodules from
an area 2 nautical miles in diameter. The first seabed disturbances were created in 1989 and after
33 years, the seabed floor has not recovered, The track can still be seen to this day.
Filter feeders that depended on suspended food had a significant
decrease in population and affected areas showed lower biodiversity than controlled areas [15]
Studies in other sites like the CCZ have also found a significant
loss of life of up to 20% when compared to controlled areas. [16]
However, the sad truth is that the alternative is to mine these materials on land,
which itself comes with environmental impacts. The
vast majority of cobalt deposits lay under the lush forests of the Congo.
To collect these metals roads need to be built, and forests need to be cut down.
Another study compared the total emissions of both land and sea based extraction methods, and
concluded that deep-sea mining of these nodules could reduce emissions by 80% for Nickol, 76% for
copper, 29% for cobalt, and 22% for Manganese [17] These reductions are primarily driven by
how these nodules are naturally occurring on the surface of the seabed, making extraction
relatively low energy, and by the fact that ships are incredibly efficient at transporting loads.
We also need to be incredibly conscious of the impending climate crisis. Ocean
temperatures are rising and with more and more carbon being absorbed into the oceans,
they are slowly becoming acidic, killing off entire coral reefs. We need to transition to
renewable energy as soon as possible, and these metals would accelerate this process.
And there lies the dilemma that we, as the human race, have to ponder. Where do
we collect the materials necessary to make a greener future? Is potentially destroying an
unknown ecological system worth it to save the ones we know for a fact are in decline. Is it
easier to find a new source of metals than to fix the problems with land-based mining?
These are the questions we need to answer before
exploiting this valuable resource in the deep dark depths of our oceans.
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