Deep thinking

The legal barriers have gone. Now experts are working on the technology that will make deep-seabed mining a reality. Rob Coppinger reports.

The sea covers 70 per cent of the world’s surface, and its marine life provides food for much of the planet’s populations. Until now exploiting its vast mineral resources has only been the stuff of fiction by Jules Verne, but that could change within a year, according to engineers working in the field.

The ocean mining industry has been slow to emerge, developing gradually over the past 30 years. It had to wait for the oil and gas industry to push forward the boundaries of submarine vehicles before it could finally be realised.

But both the technology and commercial opportunities are now coming together to create what looks set to be a lucrative business. It is as yet a fledgling industry but whether it is diamonds today, or platinum and gold in five years’ time from the Pacific, the deepest seabeds will soon no longer be just murky mysteries.

It is not vast submarines like Captain Nemo’s Nautilus that will be searching the seas for its mineral wealth, however. Small robot submarines and survey ships will do the job. The robot subs, known as remotely operated vehicles (ROVs), can now reach depths of 1.5km and plans are afoot for them to go down to 4.5km.

After decades of government and private research the technology is now low enough in price to be deployed for mining minerals that are at historically high prices.

Recent agreements through the United Nations’ International Seabed Authority now mean mining concessions for the seabed can be procured (see sidebar), and companies and consortiums are forming to take advantage of this new opportunity.

Two of these are based in the Pacific. The Sydney-based Nautilus Minerals Group (depth 1.6km) has mining concessions off Papua New Guinea, which covers some 5,000km 2 and is considered one of the richest areas in the world for gold deposits.

The other, Neptune Resources (depth 250m – 2km), based in New Zealand, has licences to exploit the Kermadic ridge off that country’s coastline. Neptune’s managing director Simon McDonald said that the company was currently exploring how it can best achieve this.

The key to seabed mining will be advances in ROVs. The leading mining ROV technology firms are based in the US and UK. One is Anglo-American remotely operated vehicle (ROV) specialist Perry Slingsby Systems, of Kirkbymoorside, near York, and also in Florida. Jon Machin is the UK-born civil engineer who is seabed technology manager at the company’s Palm Beach office.

‘The deep-water mining industry does seem finally to be getting set up,’ he confirmed.

‘We make the technology that is directly applicable, such as tracked vehicles that go down to a depth of 2.5km for oil and gas for laying down undersea pipelines. We are currently talking to several clients and expect to build something in the next 12 months.’

Machin’s background is in the oil and gas industry and his experience of the start-up ocean mining business convinces him that the two have a lot in common.

‘With mineral prices at a 10-year high investors are getting interested. The parallels with the development of the offshore oil and gas industry are quite close,’ he said.

According to Machin, while private firms have not yet built deep-ocean ROV ‘excavators’, a couple of R&D vehicles have been made by the Indian and Korean governments. Both nations have heavy ocean-mining programmes and are leaders in deep-seabed excavation.

But whether it’s governments or Machin’s firm that are involved in the likes of Nautilus Minerals’ consortium, these seabed mineral prospectors still face technical issues that present formidable practical challenges.

Anthony Wakefield is a UK consultant in this technology and knows the challenges all too well. A veteran of the oil and gas industry, he has helped design ROVs now operating off the coast of Africa. In principle he sees no technological barrier to ROVs working more than 4km down.

‘It’s expensive, but there is nothing stopping you going down 4.5km,’ he said. ‘Whereas five years ago we didn’t know what to do, today we do. The excavator is essentially a tracked ROV that uses jet pumps and could excavate 1,000 tonnes an hour at 750hp.’

At these depths significant, though not insurmountable, technical challenges remain, not least getting that horse power to the ROV. The excavation process needs the high power because of the tough crust it has to rip from the seabed.

Wakefield explained that ordinary excavation equipment won’t do the job.

‘You can’t use an ordinary toothed wheel to get this – you need a shock-wave device to break off the material from the seabed. It’s like a blunt chisel that sends a wave of energy through the crust, breaking parts of it off.’

The mining companies need not only provide enough power for the remote excavator vehicle, but also for the pumps that will drive the excavated ore back to the surface.

Substantial cables are required to carry the high-voltage electrical current. These also contain optical fibre and other communication and control-related wires for the ROV.

Wakefield points out that as the depths involved are several kilometres, the cables cannot support their own weight, so they will need to be designed to be neutrally buoyant. This is achieved by lining them with petroleum gel.

Another issue with the huge expanse of cable is its winding and unwinding. The cable is wound on to a drum on the survey ship and the drum has to be cooled as the winding operation generates heat. Ships can have up to five layers of cable on a drum to reach the necessary depths. Up until now water, poured over the drum, has been the answer but Wakefield believes there needs to be a better solution.

Once the ship has lowered the ROV, with its long cabling, and ensured the power supply is secure the excavated material needs to be brought back to the surface. Wakefield explained that while firms could use pipes simply to suck the rocks up to a few hundred metres, at 1,000m pre-processing is needed. ‘Whatyou’ve got to pre-process is the 2-4in crust you’ll break off,’ he said.

Pre-processing of the mined seabed involves crushing and sieving. Wakefield designed a pre-processing trailer in the 1980s. Yet to be built, the 6m^2 machine would crush and sieve before sending the material to the surface. This could be via a ‘shuttle’ system that uses skips on cables or a straightforward pipe and pump system.

While R&D work proceeds apace to reach these depths, there is – fortunately for the sea miners – already a substantial economic opportunity closer to the surface. Sand and gravel dredging around coastlines for the construction industry is already a $1bn(£570m) business worldwide, with companies operating in depths from 25m-150m.

The faster-growing diamond mining sector is already worth $250m (£143m) a year, with these jewels found mainly off the west coast of Africa. One of the firms involved is Diamond Fields International, based in Cape Town, South Africa.

Its engineer manager, Charles Heyes, said: ‘Our concession area is up to 110m deep. Ultra-deep is out to 300m for us. Previously diamond mining has seen single ships with divers operating at 25-30m.’

Heyes explained that the key to this littoral water exploitation is to find eluvial deposits that contain the diamonds. These deposits are actually originally from deep inland and have been brought through river systems to be left in what was a delta. But over time they have come to be in coastal waters.

These ancient river deposits are also easy to get at. This is not like diamond mining on land where the diamonds are in the bedrock. The jewels can be found in the loose gravel layer on the seabed.

For this, Diamond Fields International operates dredging technology at around 80m. This is basic excavating machinery with a large airlift system, which is a flexible pipe that uses a vacuum to suck up material.

However, global diamond supplier De Beers is already using more sophisticated technology. As the leader in this mining industry with the largest fleet of ships, it operates ROVs in up to 150m of water. Wakefield has worked with De Beers and is familiar with their technology.

‘ROVs are not autonomous yet – they do exist but they are a minority. However, De Beers has one, which is controlled when necessary by a signal cable,’ he said.

This was developed by a Namibian mining company with the help of Wakefield and Aberdeen-based firm Subsea Offshore. The Namibian firm created the ‘crawler’ for a maximum depth of 150m. But according to Wakefield, it is limited by the centrifugal pump, which is used to deliver excavated material through a pipe to the mining vessel.

De Beers bought the firm that built it and has continued its development.

Heyes said the company has carried out experiments with it down to 250m.

The incentives for the fledgling undersea mining community to go deeper and deeper are clear – the huge riches of the ocean’s bed.

With the legal barriers almost gone and the technological ones disappearing, a whole new industry is being born.

LIFTING THE BARRIERS TO SEABED EXPLORATION

Only in the past few years have international agreements been reached that clear away long-standing legal barriers to exploration of the world’s seabeds.

Building on the 1982 UN Convention on the Law of the Sea, the agreements established a framework to manage the mineral resources of the seabed beyond the limits of national jurisdiction – 200 miles from any country’s coastline.

In 2001 the International Seabed Authority (ISA) – the organisation given a UN mandate to manage the seabed outside territorial waters – handed a range of consortiums and governments the right to prospect for mineral resources across vast areas of the ocean floor.

These contracts became possible once the ISA had adopted its first legislation on prospecting and exploration for nodules in 2000. Under the regulations, each contractor has the exclusive right to explore an initial area of up to 150,000km^2.

Governments and organisations given 15-year contracts by the ISA are the China Ocean Mineral Resources Research and Development Association; Japan’s Deep Ocean Resources Development Company; the French Institut Français de Recherche pour l’Exploitation de la Mer; the Interoceanmetal Joint Organization; the governments of India and Korea; and a consortium formed by Bulgaria, Cuba, Czech Republic, Poland, Russian Federation and Slovakia.

Regions assigned by the ISA include the south-central Indian Ocean, portions of the north-eastern tropical Pacific and areas of the seabed south-east of Hawaii.

In 2002 the ISA began working on specific regulations to govern prospecting for sulphides and cobalt crusts. This process should eventually produce a mining code to cover exploration and exploitation of all seabed resources.

A WEALTH OF MINERAL RESOURCES

The seabed is littered with potato-sized ‘nodules’ of metals including copper, nickel, cobalt, gold and platinum.

These were first found 200 years ago when scientists dumped buckets into the seabed and examined their contents.

Now the seabed can be mapped acoustically using deep-tow multi-beam sonar to find the metals. The ships carrying this equipment travel at 10 knots while operating the sonar to get the best results. Visual checks are also necessary, and video cameras on the end of cables or on a remotely operated vehicle are sent down to inspect what the sonar has identified as possible mineral deposits. The Pacific Ocean is thought tobe a nodule-rich area, with Papua New Guinea of particular interest.

The geological formations of ridges close to shore appear to have the heaviest concentration of the nodules. This is because much of the ridge comes from sediment from the coastline, which contains the metals. Ridges out in the middle of oceans, by contrast, have few nodules.

However, geologists believe there is also a sub-sea process that deposits the metals. This involves material being slowly transferred from deep below the surface up to the cold sediment of the seabed.

Similar sub-sea processes provide particularly rich deposits around hydrothermal vents – chimney-like structures on the seabed that spew a hot water and mineral mix.

The minerals can be detected using water column analysis. This involves shining light through the water and analysing the absorption of that light by the particles in the water column to determine which metals are there. Up to 300 of these vents are thought to exist worldwide. Exotic ecosystems have been found to be living around them alongside the minerals. Because of concerns about damaging sea creatures, researchers are looking to exploit dead vents and the surrounding seabed.