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. Climate change is the greatest challenge facing
our planet and we need more talented engineers and scientists working to solve this problem. That’s
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