New subsea mining concepts developed

As the groundswell for subsea mining grows, new technology and seabed mining techniques are being developed.

From 2009 to last year, Aker Wirth has worked with the German Federal Institute for Geosciences and Natural Resources (BGR) to develop a new method for accessing underwater minerals and metals.

Subsea mining has come into the fore in recent years, particularly in the Pacific, which has vast quantities of seabed mineral deposits.

While the economic costs seem prohibitive, there are rich pickings to found on the seabed.

Under the sea

The minerals are characteristically found near hydrothermal vents which form above cracks in the ocean floor, typically in volcanic areas of the seabed.

They are created when water seeps into the bowels of the earth, dissolving the minerals found under the crust which is then spewed forth once more into the ocean, bringing it with the metal rich fluids.

This creates massive plumes of debris that shoots upwards and then falls back to the ocean floor; gradually building up the vents, layer up layer, until they reach a height where they eventually collapse on themselves, creating the mineral rich and often high grade, sulphide deposits over the shell of the vent.

These deposits can be up to seven times the grades typically mined on the surface.

It just so happens that a high number of these vents are found near Australia and right around the Western Pacific's rim.

Exploration licences have already been granted for seafloor exploration off New Zealand, Japan, Fiji, Tonga, the Solomon Islands and Papua New Guinea.

Australia has seen a spike in the number of applications for seabed mining, particularly in the Northern Territory, a move that forced the region to institute a moratorium on the practice.

Japan is also changing its laws after discovering a massive potential seabed rare earths deposit approximately 100 times larger than those on land.

The enormous rare earths minerals are estimated to be as large as 100 billion tonnes.

The deposit lies approximately 3.5 to 6 kilometres under the sea and cover an area of more than 11 million square metres.

At the start of this year the nation announced additional surveys of the seafloor around Japan in an attempt to uncover more deposits.

Nautilus is the most well known subsea miner currently operating.

Its Solwara 1 operation, off the coast of Papua New Guinea, has drawn intense scrutiny from both traditional miners and environmentalists.

Risks and rewards

While the rewards of subsea mining can be high, so too are the risks.

The extreme deep-sea conditions – enormous water pressure, ice-cold temperatures and complete darkness – all present huge financial and technical challenges to the mining industry when extracting the high value materials.

With this in mind, Aker Wirth and the BGR have created a new concept that allows miners to access metalliferous deposits, particularly rare earth and manganese nodules/

According to the company the system consist of two manganese nodule collectors, a transport system for conveying the material and a specially-designed production vessel.

Steffen Knodt, vice president of technology and innovation at Aker Wirth, explained: “To ensure efficient mining, a continuous transportation of raw material from the collectors via rises that are several kilometres in length is required. At such water depths, this places considerable demands on the robustness of the single components as well as on the control unit for the complete system.”

It uses airlift technology to lift the manganese nodules to the drilling vessel.

Last year it carried out studies on the system and its potential to access very deep seabed resources.

The study addressed the entire process chain from the collecting of manganese nodules to the transport of materials and right through to land-based processing; coming to the conclusion that deep-sea mining is very lucrative, even given the current prices of raw materials and anticipated price developments.

“At present, efforts are being made at an international level to first of all establish the regulations regarding mining of manganese nodules, which will then serve as a basis for the development of mining and transport systems," Knodt explained.

"As a consequence, the mining of manganese nodules will probably reach an industrial scale in five to ten years’ time," he added.

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