Mining in the deep ocean
A treasure lies buried in the sea bed. Not a pirate's bounty, no sunken ship – this is about manganese nodules, cobalt-rich crusts and massive sulphide deposits that are found in several kilometres depth. Should we lift this treasure?
First, the facts: the fist-sized manganese nodules weighing about one pound are located in 5,000 to 6,000 metres depth and consist mainly of manganese and iron oxides. Their copper, nickel and cobalt content makes them interesting for the electronic and stainless steel industry. Layer by layer, the metals that are dissolved in the seawater deposit around crystallisation cores. They have been doing this for a long time: the diameter of a manganese nodule grows by 10 to 20 millimetres in one million years. The largest deposits are located in the North-East Pacific Ocean, where in some parts half of the seabed is covered by these nodules. Whilst the cobalt-rich crust and massive sulphide deposits usually belong to island states, the manganese nodules are mainly located in international territory beyond the 200-nautical-mile zone, the exclusive economic zone. To prevent a Wild West style run on the best claims, the licences for extracting deep sea natural resources are issued for 15 years by the International Seabed Authority, headquartered in Kingston, Jamaica. This authority has been governing the deep sea raw materials on behalf of the United Nations since 1994 as a joint heritage of mankind. To apply for a licensed area of 75,000 square kilometres – a little more than the territory of Bavaria – the applicant has to previously prospect an area twice that size, that is, take ground samples, record marine life forms. This takes several years. The IMB then selects one half of this total area and allocates it free of charge to developing countries for further exploration.
The researchers from the GEOMAR – Helmholtz Centre for Ocean Research Kiel mostly focus on environmental risks. After all, the probability of commercial extraction of the deep sea raw materials is increasing. As early as in 1978, the prototype of a "harvesting machine" owned by an international syndicate did a test run, collecting manganese nodules very much like a potato harvester. At the time, the equipment could not be operated economically, yet with today's know-how this would be feasible for a successor. Also, the demand for raw materials increases due to emerging countries such as China and India. At the GEOMAR, researchers are well aware of the value of the deep sea raw materials. However, their extraction could result in a veritable "dust storm" in the Pacific Ocean, which, according to GEOMAR Director Peter Herzig, "is hardly likely to be beneficial for the ecosystem". "We see a big problem in the stirring up of sediments, which are not like our silt and coastal mud. These are mostly unhardened sediments with very fine particles." Combined with the continuous West-East deep water currents, this aforementioned storm would break loose, which could bury sensitive marine animals or at least considerably damage them. If the manganese nodules are hauled up aboard the recovery ship by way of a kind of vacuum cleaner system, this would suck up also sediments, which would have to be reintroduced, further increasing the dust storm. An unsolved problem then as it is today.
Yet another reason why a potential potato harvester has not yet been deployed on an industrial scale lies in the fact that such a device would have to withstand the water pressure at a depth of up to 6,000 metres and would have to reliably operate at one degree above freezing point. "South Korea is the technologically most advanced licensee and technically far ahead when it comes to extracting the nodules", says Carsten Rühlemann. "A South Korean collector has been successfully tested in 1,400 metres depth; a test in 5,000 metres depth is scheduled for 2016. When it comes to dressing the metals contained in the nodules, India is most likely to have a process that can be used on an industrial scale." Germany is lacking a major company that paves the way: "We no longer have a major mining corporation and the small ones are afraid of the high financial risk. After all, some 800 million Euro are required for an extraction system including metallurgic processing plant, plus 250 million Euro annual operating costs."