Mineral extraction
The potential for extracting metallic minerals from the deep sea is a concept first mooted in the 1960’s, through the publication of a report (Mero, 1965) that suggested the deep sea was full of unexplored and almost limitless supplies of cobalt, nickel and other rare and valuable metals in the form of manganese nodules. Increased exploration of the deep sea environment since this time has shown that the occurrence and quality of such resources is not nearly as rich as originally claimed, though some commercial extraction has taken place via dredging.
More recently, attention has focused on polymetallic metal sulphides – metalliferous deposits found associated with hydrothermal vent sites. Here, metals such as silver, gold, zinc, manganese, nickel and cobalt can be found in water depths of up to 4000m. Rising demand in international precious metal markets has stimulated significant interest in these deposits, despite the practical difficulties in accessing and exploiting them.
Exploitation of deep-sea mineral deposits is usually rendered problematic due to the expense and technical challenges associated with working in deep water. Historically, hydraulic pumps and submarine conveyor systems have been used to extract mineral nodules from the seabed and transport them to the surface for processing. However, modern advances in robotic technology means that the deep sea is more accessible than ever for exploration and exploitation, and a new project offshore Papua New Guinea in the Pacific Ocean plans to use robotic crawlers to mine copper and gold ore at water depths of 1600m, which is then lifted to a floating platform where is it dewatered and transferred to a barge for transport to processing plants on land.
Extraction of metals from the deep sea is not without environmental consequences. Disturbance of the seafloor and upper sediment layers will not only destroy habitats, but will also generate huge clouds of suspended sediment, effectively choking both benthic (seafloor-dwelling) creatures and those living in the water column. This impact is already known to be devastating where bottom trawling for fish has distrubed seafloor sediments in or near areas of coral reef. Other accidental damage such as chemical or oil/lubricant spillage, leaks and pollution are also a risk to the good health of the marine environment in areas being mined.
The International Seabed Authority (ISA) was established in 1982 under the United Nations Convention on the Law of the Sea to regulate commercial activity on the seafloor (principally seabed mining) in areas beyond countries' national jurisdiction (normally those areas outside a country's Exclusive Economic Zone, which extends out 200 nautical miles).
Mero, J.L. (1965) The Mineral Resources of the Sea. Elsevier, Amsterdam.
