Deep sea mining is a mineral retrieval process that takes place on the ocean floor. Ocean mining sites are usually around large areas 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. As with all mining
operations, deep sea mining raises questions about its potential
environmental impact. Environmental advocacy groups such as Greenpeace
and the Deep sea Mining Campaign
have argued that seabed mining should not be permitted in most of the
world's oceans because of the potential for damage to deepsea ecosystems
and pollution by heavy metal laden plumes.
Brief history
In the 1960s the prospect of deep-sea mining was brought up by the publication of J. L. Mero's Mineral Resources of the Sea. The book claimed that nearly limitless supplies of cobalt, nickel and other
metals could be found throughout the planet's oceans. Mero stated that these metals occurred in deposits of manganese nodules, which appear as lumps of compressed flowers on the seafloor at
depths of about 5,000 m. Some nations including France, Germany and the United States sent out research vessels in search of nodule deposits. One such vessel was the Glomar Explorer.
Initial estimates of deep sea mining viability turned out to be much
exaggerated. This overestimate, coupled with depressed metal prices, led
to the near abandonment of nodule mining by 1982. From the 1960s to
1984 an estimated US $650 million had
been spent on the venture, with little to no return.
Over the past decade a new phase of deep-sea mining has begun. Rising demand for precious metals in Japan, China, Korea and India
has pushed these countries in search of new sources. Interest has
recently shifted toward hydrothermal vents as the source of metals
instead of scattered nodules. The trend of transition towards an
electricity-based information and transportation infrastructure
currently seen in western societies further pushes demands for precious
metals. The current revived interest in phosphorus nodule mining at the
seafloor stems from phosphor-based artificial fertilizers being of
significant importance for world food production. Growing world
population pushes the need for artificial fertilizers or greater
incorporation of organic systems within agricultural infrastructure.
Currently, the best potential deep sea site, the Solwara 1 Project, has been found in the waters off Papua New Guinea, a high grade copper-gold resource and the world's first Seafloor Massive Sulphide (SMS) resource. The Solwara 1 Project is located at 1600 metres water depth in the Bismarck Sea, New Ireland Province. Using ROV (remotely operated underwater vehicles)
technology developed by UK-based Soil Machine Dynamics, Nautilus
Minerals Inc. is first company of its kind to announce plans to begin
full-scale undersea excavation of mineral deposits.
However a dispute with the government of Papua-New Guinea delayed
production and its now scheduled to commence commercial operations in
early 2018.
The world's first "large-scale" mining of hydrothermal vent
mineral deposits was carried out by Japan in August - September, 2017. Japan Oil, Gas and Metals National Corporation (JOGMEC) carried out this operation using the Research Vessel Hakurei. This mining was carried out at the 'Izena hole/cauldron' vent field
within the hydrothermally active back-arc basin known as the Okinawa Trough which contains 15 confirmed vent fields according to the InterRidge Vents Database.
Laws and regulations
The international law–based regulations on deep sea mining are contained in the United Nations Conventions on the Law of the Sea from 1973 to 1982, which came into force in 1994. The convention set up the International Seabed Authority (ISA), which regulates nations’ deep sea mining ventures outside each nations’ Exclusive Economic Zone
(a 200-nautical-mile (370 km) area surrounding coastal nations). The
ISA requires nations interested in mining to explore two equal mining
sites and turn one over to the ISA, along with a transfer of mining
technology over a 10- to 20-year period. This seemed reasonable at the
time because it was widely believed that nodule mining would be
extremely profitable. However, these strict requirements led some
industrialized countries to refuse to sign the initial treaty in 1982.
The US abides by the Deep Seabed Hard Mineral Resources Act,
which was originally written in 1980. This legislations is largely
recognized as one of the main concerns the US has with ratifying UNCLOS.
Within the EEZ of nation states seabed mining comes under the
jurisdiction of national laws. Despite extensive exploration both
within and outside of EEZs, only a few countries, notably New Zealand,
have established legal and institutional frameworks for the future
development of deep seabed mining.
Papua New Guinea was the first country to approve a permit for
the exploration of minerals in the deep seabed. Solwara 1 was awarded
its licence and environmental permits despite three independent reviews
of the environmental impact statement mine finding significant gaps and
flaws in the underlying science ( see http://www.deepseaminingoutofourdepth.org/report/).
The ISA has recently arranged a workshop in Australia where
scientific experts, industry representatives, legal specialists and
academics worked towards improving existing regulations and ensuring
that development of seabed minerals does not cause serious and permanent
damage to the marine environment.
Resources mined
The
deep sea contains many different resources available for extraction,
including silver, gold, copper, manganese, cobalt, and zinc. These raw
materials are found in various forms on the sea floor.
Minerals and related depths
| Type of mineral deposit | Average Depth | Resources found |
|---|---|---|
| Polymetallic nodules | 4,000 – 6,000 m | Nickel, copper, cobalt, and manganese |
| Manganese crusts | 800 – 2,400 m | Mainly cobalt, some vanadium, molybdenum and platinum |
| Sulfide deposits | 1,400 – 3,700 m | Copper, lead and zinc some gold and silver |
Diamonds are also mined from the seabed by De Beers and others.
Nautilus Minerals Inc and Neptune Minerals are planning to mine the
offshore waters of Papua New Guinea and New Zealand.
Extraction methods
Recent technological advancements have given rise to the use remotely operated vehicles
(ROVs) to collect mineral samples from prospective mine sites. Using
drills and other cutting tools, the ROVs obtain samples to be analyzed
for precious materials. Once a site has been located, a mining ship or
station is set up to mine the area.
There are two predominant forms of mineral extraction being
considered for full-scale operations: continuous-line bucket system
(CLB) and the hydraulic suction system. The CLB system is the preferred
method of nodule collection. It operates much like a conveyor-belt,
running from the sea floor to the surface of the ocean where a ship or
mining platform extracts the desired minerals, and returns the tailings to the ocean.
Hydraulic suction mining lowers a pipe to the seafloor which transfers
nodules up to the mining ship. Another pipe from the ship to the
seafloor returns the tailings to the area of the mining site.
In recent years, the most promising mining areas have been the
Central and Eastern Manus Basin around Papua New Guinea and the crater
of Conical Seamount to the east. These locations have shown promising
amounts of gold in the area's sulfide deposits (an average of 26 parts per million).
The relatively shallow water depth of 1050 m, along with the close
proximity of a gold processing plant makes for an excellent mining site.
Deep sea mining project value chain can be differentiated using
the criteria of the type of activities where the value is actually
added. During prospecting, exploration and resource assessment phases
the value is added to intangible assets, for the extraction, processing
and distribution phases the value increases with relation to product
processing. There is an intermediate phase – the pilot mining test which
could be considered to be an inevitable step in the shift from
“resources” to “reserves” classification, where the actual value starts.
Exploration phase involves such operations as locating, sea
bottom scanning and sampling using technologies such as echo-sounders,
side scan sonars, deep-towed photography, ROVs, AUVs. The resource
valuation incorporates the examination of data in the context of
potential mining feasibility.
Value chain based on product processing involves such operations
as actual mining (or extraction), vertical transport, storing,
offloading, transport, metallurgical processing for final products.
Unlike the exploration phase, the value increases after each operation
on processed material eventually delivered to the metal market.
Logistics involves technologies analogous to those applied in land
mines. This is also the case for the metallurgical processing, although
rich and polymetallic mineral composition which distinguishes marine
minerals from its land analogs requires special treatment of the
deposit. Environmental monitoring and impact assessment analysis relate
to the temporal and spatial discharges of the mining system if they
occur, sediment plumes, disturbance to the benthic environment and the
analysis of the regions affected by seafloor machines. The step involves
an examination of disturbances near the seafloor, as well as
disturbances near the surface. Observations include baseline comparisons
for the sake of quantitative impact assessments for ensuring the
sustainability of the mining process.
Environmental impacts
Research shows that polymetallic nodule fields are hotspots of abundance and diversity for a highly vulnerable abyssal fauna.
Because deep sea mining is a relatively new field, the complete
consequences of full-scale mining operations on this ecosystem are
unknown. However, some researchers have said they believe that removal
of parts of the sea floor will result in disturbances to the benthic layer, increased toxicity of the water column and sediment plumes from tailings. Removing parts of the sea floor could disturb the habitat of benthic organisms, with unknown long-term effects.
Aside from the direct impact of mining the area, some researchers and
environmental activists have raised concerns about leakage, spills and corrosion that could alter the mining area’s chemical makeup.
Among the impacts of deep sea mining, sediment plumes could have
the greatest impact. Plumes are caused when the tailings from mining
(usually fine particles) are dumped back into the ocean, creating a
cloud of particles floating in the water. Two types of plumes occur:
near bottom plumes and surface plumes. Near bottom plumes occur when the tailings are pumped back down to the mining site. The floating particles increase the turbidity, or cloudiness, of the water, clogging filter-feeding apparatuses used by benthic organisms.
Surface plumes cause a more serious problem. Depending on the size of
the particles and water currents the plumes could spread over vast
areas. The plumes could impact zooplankton and light penetration, in turn affecting the food web of the area.
Controversy
An article in the Harvard Environmental Law Review
in April 2018 argued that "the 'new global gold rush' of deep sea
mining shares many features with past resource scrambles – including a
general disregard for environmental and social impacts, and the
marginalisation of indigenous peoples and their rights".
The Foreshore and Seabed Act (2004) ignited fierce indigenous
opposition in New Zealand, as its claiming of the seabed for the Crown
in order to open it up to mining conflicted with Māori claims to their
customary lands, who protested the Act as a "sea grab." Later, this act
was repealed after an investigation from the UN Commission on Human
Rights upheld charges of discrimination. The Act was subsequently
repealed and replaced with the Marine and Coastal Area Bill (2011). However, conflicts between indigenous sovereignty and seabed mining continue. Organizations like the Deep Sea Mining Campaign
and Alliance of Solwara Warriors, comprising 20 communities in the
Bismarck and Solomon Sea, are examples of organizations that are seeking
to ban seabed mining in Papua New Guinea, where the Solwara 1 project
is set to occur, and in the Pacific. They argue primarily that
decision-making about deep sea mining has not adequately addressed Free
Prior and Informed Consent from affected communities and have not
adhered to the Precautionary Principle,
a rule proposed by the 1982 UN World Charter for Nature which informs
the ISA regulatory framework for mineral exploitation of the deep sea.
