Dubbed the most hostile environment on earth, the deep ocean is a vast and daunting place.

From monumental pressures (equivalent of 50 jumbo jets placed on top of a person) to unbelievable depths (at some points in the ocean Mount Everest would be completely swallowed up), there are some extreme challenges in exploring the bottom of the oceans.

However, there are also prospective rewards at stake, including the answer to a potential future shortage of key battery mineral components and other rare earth materials.

There are three main deep sea mining methods aimed at different resource types: polymetallic nodule recovery, polymetallic crust recovery from seamounts and polymetallic sulphide recovery.

Of the three methods, polymetallic nodule recovery is the least environmentally damaging and the one that has garnered the most attention, with original research into this method beginning in the 1970s.

One of the reasons the exercise has not taken off in the last 50 years is the difficult technical challenges associated with mining in such an unknown landscape, however, for International Union for Conservation of Nature (IUCN) Global Marine Program Principal Marine and Polar Scientist Carl Gustaf Lundin, the biggest challenge is the sheer cost of the enterprise.

“By the time you have paid for the development of special equipment and got everything up and running I would imagine most of the big companies would have already gone out of business,” he said.

“I actually don’t think anyone will make any money off this exercise for at least the next 10 years, and the only real winners will be the manufacturers who will be building the big specialised extraction equipment.”

Two companies con dent Mr Lundin is wrong are Nautilus Minerals, a Canadian company looking to mine o  the coast of Papua New Guinea at its Solwara 1 deposit and DeepGreen Metals, looking to harvest nodules in the Clarion Clipperton Zone, a huge potential resource occupying a swathe of the Pacific Ocean the size of the US.

For both of these companies there are significant benefits to pursuing minerals underwater. DeepGreen recently announced a combined seafloor inferred resource estimate of 909 million tonnes of wet polymetallic nodules grading 1.3 per cent nickel, 29.2 per cent manganese, 1.1 per cent copper and 0.2 per cent cobalt, with a mean nodule abundance of 13kg per square metre based on a nodule abundance cut-off of 4kg per square metre.

In spite of the potential benefits, there are a number of arguments against the exercise, especially from environmental groups, but DeepGreen Chairman and CEO Gerard Barron said opponents needed to look at the bigger picture.

“We have to view the planet as a single entity and think about what is in the best interests of the planet as a whole,” he said.

“The Clarion Clipperton Zone is known as an abyssal plain, as it is the most deserted barren environment on the planet. It just happens to be underwater. I would much rather be focusing on a place such as this, which has high grades of the minerals and metals we will need most in the future, than trying to cut down huge swathes of rainforest for lower-grade metals.

“We obviously need to convince the public this is a responsible and safe use of the ocean’s resources and that is why we are putting so much effort – years of study actually – into gathering the data to make this industry acceptable to the world.

“We will also need to ensure all the players in the deep ocean mining sector follow strict protocols.”

Although there is a definite need for strict protocols to be put in place, similar to those seen for terrestrial-based mining operations, Mr Lundin said the regulations currently being put together by the International Seabed Authority (ISA) were more lax than they needed to be.

As an example, he said if there was a danger of a whole species being wiped out on land it would completely halt proceedings, but there was no such measure in place for seabed mining at the moment.

“I think this will probably change as exploration changes to exploitation and more companies and countries get involved, but I just hope it isn’t already too late for some species and marine ecosystems by that point,” Mr Lundin said.

For Nautilus Minerals, the biggest challenge has already been overcome, according to its Corporate Communications Manager Noreen Dillane, who said being trailblazers in a potentially revolutionary exercise was extremely exciting.

“Designing and building a system that will allow the company to mine the ocean floor in a responsible, environmentally friendly, cost-effective and sustainable manner that has the potential to change mining forever was perhaps our biggest challenge,” she said. “The system we now have was developed in consultation with regulators, scientists and local people.

“It’s always a challenge to be the first to do something on this scale.”

Turf competition

The big questions surrounding deep sea mining for a number of companies is whether it will be a viable alternative to terrestrial-based operations and, if so, how long it will be before it gets to that point.

Mr Lundin said some parties seemed to be erring on the side of caution.

“There are a number of big mining nations that are taking a fairly dim view on the process, which suggests to me they feel there is a threat to terrestrial mining there,” he said.

A significant advantage for deep sea mining is the lack of any permanent mining equipment needed, as many of the excavation techniques use remotely controlled or automated machines that slowly track along the seabed.

For Ms Dillane and Nautilus Minerals, the biggest advantages of seabed mining include a lack of tailings, minimal pre-stripping of sediment, low fresh water needs, no vegetation stripping, no fresh-water catchment issues and minimal rehabilitation costs thanks to the lack of permanent infrastructure.

Mr Barron said there were a number of advantages for deep sea mining over the land-based operations, but referred these advantages back to the polymetallic nodule recovery that DeepGreen is working towards. He said nodule collection was a complete reframe of conventional metals extraction.

“You start with a 2D resource that you can easily go down and see with an autonomous underwater vehicle so there are no surprises, as opposed to needing to infer the size of a 3D resource through a laborious process of sensing, drilling and geological modelling,” he said.

“Your grades are 10 times higher than on land. You don’t have to drill and blast hard rock and then move and process a tonne of rock for a few kilograms of product – you go down on the seabed floor, collect rocks and 100 per cent of what you collect is turned into saleable material. No waste, no toxic tailings dams.

“We do impact ocean floor species that live on nodules and this is something we are concerned about, which is why we are investing in several years of environmental studies and environmental engineering to make sure we do everything we can to minimise that impact.

“Polymetallic nodule collection will enable us to retrieve a major amount of metals like cobalt, nickel and copper in an environmentally responsible way without hurting the ocean.”

Both Mr Lundin and Mr Barron highlighted a lack of disruption to human life as a major additional bonus, although Mr Lundin said the damage to non-human populations could be substantial.

“There are a number of creatures and species that have never encountered humans, so the level of disruption to those could be very big,” he said.

“Many of these ecosystems are very fragile and the impacts could last for centuries.”

A sinking ship or the last life raft to safety?

Although companies looking to take part in this journey will need to complete lengthy environmental impact statements, the real impact of deep sea mining is as yet unknown.

“Even in the water column there can be some very significant impacts when nodules are brought to the surface and separated from bottom sediments,” Mr Lundin said.

“Below the seabeds there is magma, so when we disturb the areas like hydrothermal vents there could be a chance of causing a volcanic reaction, which could be a very risky and potentially costly exercise.

“Our level of knowledge of the oceans is comparatively very limited against our knowledge of land-based operations.”

Despite this, Ms Dillane said seabed mining was an inevitable enterprise due to the world’s rising demand for minerals, while Mr Barron said the push towards deep ocean mining was growing across the world.

“Consortiums and countries are actively investing in and researching deep ocean mining,” he said. “As one of the most advanced players in this nascent sector, our view is it must be done responsibly, putting the health of the ocean first. That’s why we work so closely with the UN International Seabed Authority and scientists to make sure the best science is carried out and all the environmental precautions are in place.

“The world needs a supply of these metals for our future, but they must be brought to market in a planet-friendly way.

“We could use blockchain to prove the ethical and clean source of these metals, which means an electric vehicle manufacturer or a smart phone maker could guarantee consumers they have ethical metals inside their products.

“This will be an important attribute for companies and brands as we move into a world that will need more of these metals for the electric vehicle future.”

Polymetallic nodule recovery

This method involves a remotely operated collector slowly moving along the seafloor collecting small potato-sized nodules that have formed in that place for millions of years. Inside these nodules is a combination of metals including cobalt, manganese, nickel, copper or a variety of rare earth elements, depending on the composition of the nodule in question.

Once picked up by the collector, the nodules are suctioned up to the surface via a riser pipe attached to a production support vessel, where they are stored and dewatered.

DeepGreen Metals is looking to implement this method when in production.

“Our focus is on the vast fields of polymetallic nodules that naturally occur on the surface of the deep – ocean floor, more than 3km under the ocean,” Mr Barron said. “This means we will not be drilling, grinding or using explosives to collect nodules. Instead, we simply have to lift them off the surface of the ocean with a specially designed harvester that gently sucks them up and brings them to the surface.”

Polymetallic sulphide recovery

This method sees an excavator disaggregating deposits on the sea floor before a lifting system brings the ore to the surface where a surface vessel stores the material and provides support and power for the equipment on the sea floor.

Nautilus Minerals is looking to implement this method and has commissioned a range of high-tech equipment.

“The excavation and collection has been split into three individual tasks which will each be carried out by a different vehicle,” Ms Dillane said.

“The auxiliary cutter is designed as the pioneering machine which prepares the rugged sea bed for the more powerful bulk cutter. These two machines gather the excavated material. The third vehicle, the collecting machine, will collect the cut material by drawing it in as seawater slurry with internal pumps and pushing it through a flexible pipe to the subsea pump.”

Polymetallic crust recovery from seamounts

Due to the concentrations of metals in polymetallic crusts, this method provides the largest economic interest, but it also comes with the biggest environmental effects and is the most diffcult to complete.

The main basis of this method is fragmenting and removing crusts cemented to hard substrates and transporting the pieces to the surface.

Image: DeepGreen CEO Gerard Barron holding a polymetallic nodule.