Mining at Sea

Remote-controlled 75-tonnes clamshell for excavations down to 1,000 metres undersea. (Photo: Seatools)

As the economy picks up and metal prices continue to rise, plans and projects to extract precious ores from the deep sea are regaining strength. The Dutch offshore and shipping industries are in good starting position.

There are treasures waiting at the bottom of the deep sea. Gold, silver, copper, and manganese are all to be found in exceptionally high concentrations in the sulphide deposits created by hydrothermal vents at about 1,400 to 3,700 meters below the ocean’s surface.

Subsea mining was first proposed in J.L. Mero’s 1960 publication, ‘Mineral Resources of the Sea’, which noted the sheer limitless supply of cobalt, nickel and other materials in deposits of manganese nodules at depths of 5,000 metres. But after some initial expeditions on the seafloor, global metal prices began falling due to the weak economy of the 1980s, and hence the prospect of nodule mining was abandoned. But recent increases in demand and prices of metals have put deep-sea mining back on the agenda. This time however it’s targeted at the volcanic hydrothermal vents, or black smokers, where hot mineral-rich water springs from the ocean floor, creating towering deposits compiled from a zoo of metals and sulphur.

Front runner in deep-sea mining of Seafloor Massive Sulphide (SMS) resources is currently Nautilus Minerals (UK) with a concession for mining gold and copper at a depth of 1,600 metres off the coast of Papua-New Guinea. First production is expected in early 2013. Like Canadian company Neptune Minerals, operating near New Zealand, Nautilus will also venture into phosphate mining. Dredging expert, Professor Cees van Rhee (from the faculties of Mechanical, Maritime and Materials Engineering, and Civil Engineering and Geosciences), expects that phosphate mining, taking place nearer to shore and at a limited depth (400 metres), will be one of the first profitable maritime mining activities. Van Rhee: “The price of rock phosphate has peaked to USD $400 per tonne. It can be mined from the sea at approximately $100 per tonne.”

The dredging expert says it’s not so much a question of if deep-sea mining will be developed, but when: “It’s inevitable. Just like oil and gas exploration and production, which began on land, then went near-shore and eventually ever further and deeper offshore. Mining shows the same tendency.”

“It’s like dredging at great depths,” says Jan Frumau, managing director of Seatools, near Rotterdam. At a meeting of the Dutch Shipbuilders Society this Thursday, Frumau will deliver a lecture on deep-sea mining. He envisions a fleet of heavy-duty, remotely operated vehicles (ROV’s) operating on the ocean floor, nibbling off the SMS deposits. The electrically powered equipment needs to be extremely tough to operate reliably at 200 bars of hydrostatic pressure. Bringing equipment from the seafloor to the surface and back for repair will take several hours.

Last year professors Van Rhee and Rene Huijsmans (3mE), together with a number of maritime and dredging companies, presented a research proposal at technology fund, STW, called Seaflore, which aimed to develop systems and methods for deep-sea mining, especially targeted at rare-earth metals that are alarmingly becoming scarce.

However, the proposal was rejected because STW felt there was no ‘problem-owner’; that is, a Dutch industry prospecting into deep-sea mining and in need of new technology. True, the professors say, but we do have, close to Rotterdam, a large concentration of leading companies in dredging, offshore lifting and construction, such as Boskalis, Heerema, Fugro and IHC-Merwede, to name a few. IHC-Merwede is starting up a new business unit to support mining industries venturing into deep-sea mining.

Despite STW’s rejection, a number of research projects have been set up at TU Delft. One PhD student will study the vertical hydraulic transport of mine tailings to the surface, while another will work on haptic feedback for underwater robots in Professor Frans van der Helm’s (3mE) STW-supported programme, H-Haptic.

Together with Wageningen University’s research institute Imares, and a team of international researchers, Prof. van Rhee would also like to set up a research project exploring the environmental impact. Environmentalists have expressed concern about the impact of mining activities on deep-sea aquatic life, yet very little is known about the deep sea ecology.