Deep sea minerals have been seen as a potential new source for in demand rare earth minerals and the offshore industry is closely eyeing its potential for a new and innovative revenue stream.
In terms of monetary value, National Geographic estimates that there is enough gold on the sea floor to give every person alive nine pounds each, worth about $150 trillion or $21,000 per person.
Despite these estimates, one of the main stumbling blocks remains the ease of resource accessibility.
Deep sea mining is a relatively new mineral retrieval process that involves the extraction of rare earth mineral resources around large areas of polymetallic (containing or involving several metals or their ores) nodules or active and extinct hydrothermal vents (fissure in a planet’s surface from which geothermally heated water issues.) at depths of up to 4000 metres below the ocean’s surface.
These minerals may include silver, gold, copper, manganese, cobalt, zinc etc. and are mined using either hydraulic pumps or bucket systems that take ore to the surface to be processed.
Following preliminary studies and investigation by researchers and deep-sea miners, two main destinations for exploration include (1) the sites of hydrothermal vents which in some cases are huge seafloor sulphide deposits (stadium size mounds of metal rich-rock deposited by intense hot springs at mid-oceanic ridges and (2) Tennis ball-sized mineral rich nodules on the seabed that can be harvested as opposed to mined.
Initial studies, testing and development have revealed that potential mining of these resources, can be achieved in a number of ways. Firstly, the sending down of remotely operated vehicles (ROVs) to dredge nodules or mineral-rich crust.
That being said, this technology has a number of limitations as this process can be time-consuming and the ROVs have a weight limitation per trip. A second way would be to utilise a floating platform above the concerned mining site with an attached conveyor belt to bring the material up to the surface where it is then sorted and separated.
Alternatively, a hydraulic suction system could be implemented. Once the valuable materials have been extracted, processed and separated from the surrounding rock, the spent tailings (waste materials) are then dumped over the side of the platform.
To this effect, the acid test will be the start of commercial sea bed mining due to begin by 2019, 1.6 km below waters off Papua New Guinea by Nautilus Minerals who plan to release three giant crawling machines to grind up rocks rich in copper, zinc and gold and pump the slurry up to a custom-built surface ship at a rate of over 3000 tonnes a day.
Despite the aforementioned potential benefits of Deep Sea mining, there are a number of significant environmental concerns; due to the fragile ecosystem that exists within deep sea environments.
This is further complicated by the ironic relationship between the push for renewable energy and the necessity of rare earth minerals to fuel that push. One of the early underwater mining investigations from the Tropic Seamount, an underwater mountain that stands about 3,000m tall in the Canary Islands brought back samples to the surface that contained the scarce substance tellurium in concentrations 50,000 times higher than in deposits on land.
Tellurium is used in a type of advanced solar panel and raises the difficult question as to whether the push for renewable energy may encourage mining of the seabed. 2,670 tonnes of tellurium on this single seamount represents one-twelfth of global supply. Additionally, the rocks also contain rare earth elements that are used in wind turbines and electronics.
Overarching research and development within the offshore industry should potentially look to answer the question as to whether the benefit of renewable energy outweighs the potential fallout of mining in particularly fragile and poorly understood ecosystems.
Sylvester, Consultant, Leyton UK
- Offshore Engineer – http://www.oedigital.com/energy/item/16286-deep-sea-mining
- National Geographic – https://news.nationalgeographic.com/2016/07/deep-sea-mining-five-facts/
- MIT Technology Review – https://www.technologyreview.com/s/604183/a-huge-deep-sea-metal-find-could-help-build-our-green-energy-future/
- Mining Technology – http://www.mining-technology.com/features/featureseafloor-mining-the-deepgreen-method-5889044/
- TechnoMine – http://technology.infomine.com/reviews/deepseamining/welcome.asp?view=full