Deep Sea Mining: Is the Future 20,000 Leagues Under the Sea?

Julian Smith Writer
graphic of a deep sea mining ship

The world’s first deep sea mining project could lead to new mineral sources, but can modern technology and regulations mitigate environmental risks?

Jules Verne described men mining the ocean floor in his 1870 book Twenty Thousand Leagues Under the Sea, but it took nearly 150 years for reality to catch up.

The vast and virtually unexplored deep ocean holds a wealth of metals and minerals. Canadian company Nautilus Minerals—which shares a name with the ship in Verne’s story—plans to have the world’s first commercial deep sea mining (DSM) project underway by early 2018 off the coast of Papua New Guinea.

deep sea mining diagram

DSM is a process where professionals use remotely operated vehicles (ROVs) to collect deposits of minerals such as gold, zinc and silver from the ocean floor.

“On the sea floor are the largest known resources of things like copper, nickel, and cobalt, at quite high grade compared to land,” said Nautilus CEO Mike Johnson. Higher concentrations of minerals mean that mining operations can be smaller than surface mines.

Proponents like Johnson believe deep sea mining is an economical way to avoid some of the harmful environmental side effects inherent with traditional surface mining.

ROV in the process of taking chimney sample

However, some ocean scientists worry that DSM could be destructive to this delicate and under-explored ecosystem.

Surface mines are getting bigger and more expensive, as production costs rise and large deposits of high-grade ore become harder to find. This creates a vicious circle where mines have to become even more massive to be profitable, Johnson said.

Meanwhile, demand is soaring for everything from nickel for rechargeable smartphone batteries to rare earth elements used in the aerospace and alternative-energy industries.

The Case for DSM

In some places, valuable minerals are literally lying around in lumps on the ocean floor waiting to be scooped up. These “polymetallic nodules,” usually the size of golf balls or potatoes, lie scattered on the sea floor between 13,000 and 20,000 feet.

The slow-growing nodules are rich in minerals like manganese, nickel, cobalt, copper, lithium, manganese, molybdenum, iron and rare earth elements. Johnson said these could be relatively easy to harvest by remotely-operated machines crawling across the seabed, although the technology is still being perfected.

a Seafloor Production Tools (SPT) with tank treads and giant grinding teeth
CM Nautilus

In the meantime, Nautilus Minerals’ Solwara 1 project will target a different kind of deposit: mineral-rich hydrothermal vents, also called Seafloor Massive Sulfide (SMS) deposits, 5,000 feet deep.

There are about 300 known hydrothermal vent sites around the world. They’re essentially underwater hot springs, where seawater heated to 700°F or more flows up out of the earth’s crust and deposits suspended minerals into chimneys and other formations. The unique combination of heat and chemistry often supports ecosystems of unique and bizarre deep-sea life.

The chimneys can stand as tall as 50 feet high, although many have fallen over.mineral deposits on a rock on the ocean floor

Nautilus estimates the inactive vents at the Solwara 1 SMS site could produce 138,000 tons of copper and 350 tons of gold. The ore is very high grade, Johnson said, averaging nearly 8 percent copper compared to an average of 0.6 percent on land in 2015.

To collect the minerals, Nautilus has built a trio of massive remote-controlled robotic machines called Seafloor Production Tools (SPTs). With tank treads and giant grinding teeth, each SPT looks like a piece of post-apocalyptic construction machinery.

Nautilus machines used for deep sea mining
Nautilus machines

The 275-ton auxiliary cutter, standing more than 20 feet high, will flatten rough terrain and create benches for the 340-ton bulk cutter to work on. The 220-ton collecting machine will gather up the sand, gravel and silt the cutters leave behind.

At least two people will control each SPT at all times using multiple visualization technologies, including live-streaming video. Operators sit in front of multiple video screens, controlling the machines with joysticks.

“It’s intense, like playing a video game for eight or 10 hours,” said Johnson. GPS, sonar and unmanned ROVs monitor the action continuously to avoid accidents.

Control Room for the SPTs

The slurry rises to the surface through a pipe connected to a production support vessel. Once the seawater is removed, filtered and pumped back down to the sea floor, the solid ore is ready to transport for processing.

Johnson said that the advances they have made in remote controlled mining robotics are already drawing interest from European countries looking to reopen old flooded mines.

The Environmental Impacts

DSM may happen far out of sight, said conservation biologist Richard Steiner, but that doesn’t mean it’s environmentally benign.

“It cannot be done in a non-destructive manner,” he said. “There’s no question it will pose massive environmental impacts.”

robotic arm grabbing a rock

The deep ocean is both the largest and least understood habitat on the planet, Steiner said, which makes it hard to predict the impact of mining. Sediment plumes, leaks and spills, and mixing of different parts of the water column could affect sea life in potentially catastrophic ways.

The ecosystems that surround hydrothermal vents in particular are rare, unique and still mostly a mystery; no one knew they existed until the late 1970s.

“There could be some enormous pharmaceutical benefits to preserving these species we haven’t even identified yet,” Steiner said. He wants to avoid any dangerous results that might come from poor scientific understanding, arrogance and greed.

Seafloor production system graphic

Johnson pointed out that Nautilus has consulted with a long list of experts, including people at the Scripps Institution of Oceanography and Woods Hole Oceanographic Institution. Studies done for an environmental assessment of the Solwara project indicated that sediment disturbance from mining would be localized, and the effort will leave no tailings or waste material behind. (All the ore will be processed on land in China, where any leftovers will end up.)

“We’ve designed the whole system to minimize impact,” Johnson said. “This is as close to a sustainable mining project as you’ll get.”

Transporter Bridge Teesside
Transporter Bridge Teesside

Steiner disagreed with many of the findings in the environmental assessment, and recommends at least a decade more of scientific research before giving DSM the green light.

Groups such as Greenpeace are also warning against potential risks.

But 20,000 leagues under the sea, the ball is rolling. The UN’s International Seabed Authority has already approved at least 19 deep ocean prospecting licenses for governments and companies around the world.


All images are from Nautilus Minerals.

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