The most valuable of the marine mineral resources is petroleum. About 15% of the world's oil is produced offshore, and extraction capabilities are advancing. One of the largest environmental impacts of deep sea mining are discharged sediment plumes which disperse with ocean currents and thus may negatively influence the marine ecosystem. Coal deposits known as extensions of land deposits , are mined under the sea floor in Japan and England.
Deep sea mining is a growing subfield of experimental seabed mining that involves the retrieval of minerals and deposits from the ocean floor found at depths of 200 metres (660 ft) or greater. As of 2021, the majority of marine mining efforts are limited to shallow coastal waters only, where sand, tin and diamonds are more readily accessible. There are three types of deep sea mining that have generated great interest: polymetallic nodule mining, polymetallic sulphide mining, and the mining of cobalt-rich ferromanganese crusts. The majority of proposed deep sea mining sites are near of polymetallic nodules or active and extinct hydrothermal vents at 1,400 to 3,700 metres (4,600 to 12,100 ft) below the ocean’s surface. The vents create globular or massive sulfide deposits, which contain valuable metals such as silver, gold, copper, manganese, cobalt, and zinc. The deposits are mined using either hydraulic pumps or bucket systems that take ore to the surface to be processed. Marine minerals include sea-dredged and seabed minerals. Sea-dredged minerals are normally extracted by dredging operations within coastal zones, to maximum sea depths of about 200 m. Minerals normally extracted from these depths include sand, silt and mud for construction purposes, mineral rich sands such as ilmenite and diamonds. As with all mining operations, deep sea mining raises questions about its environmental impact. There is a growing debate about whether deep sea mining should be allowed or not. Environmental advocacy groups such as Greenpeace and the have argued that seabed mining should not be permitted in most of the world's oceans because of the potential for damage to deep sea ecosystems and pollution by heavy metal-laden plumes. Prominent environmental activists and state leaders have also called for moratoriums or total bans due to the potential of devastating environmental impacts. Some argue that there should be a total ban on seabed mining. Some anti-seabed mining campaigns have won the support of large industry such as some of the technology giants, and large car companies. However, these same companies will be increasingly reliant on the metals seabed minerals can provide. Some scientists argue that seabed mining should not go ahead, as we know such a relatively small amount about the biodiversity of the deep ocean environment. Individual countries with significant deposits of seabed minerals within their large EEZ’s are making their own decisions pertaining to seabed mining, exploring ways of undertaking seabed mining without causing too much damage to the deep ocean environment, or deciding not to develop seabed mines.Some companies are attempting to build polymetallic deep sea mining equipment which does no serious harm and preservers the marine habitat. As of 2022 there was no commercial mining of seabed minerals. However, the International Seabed Authority has granted 19 exploration licenses for polymetallic nodules, within the Clarion Clipperton Zone. The Cook Islands Seabed Minerals Authority (SBMA) has granted 3 exploration licenses for polymetallic nodules within their EEZ. There is the potential for mining at a range of scales within the oceans from small to very large. Technologies involved in the mining of seabed minerals would be highly technological, and involve a range of robotic mining machines, as well as surface ships, and metal refineries at onshore locations. One vision for the post-fossil fuel world will rely on wind farms, solar energy, electric cars, and improved battery technologies: these use a high volume and wide range of metallic commodities including ‘green’ or ‘critical’ metals many of which are in relatively short supply. Seabed mining could provide a near-term solution to the provision of many of these metals, though only serves to worsen the fundamental problems posed by extraction.
