A little-known method for retrieving minerals, deep sea mining was attempted with limited success in the past, with new plans still in the beginning stages. As we have seen from past mining practices that have left massive scars on the earth’s surface, many of which will take decades or even hundreds of years to heal, the easiest way to get to mineral deposits is not always the best. Deep sea mining is a risky procedure that holds potential for both disaster and a way forward.
Deep Sea Mining Procedures
Potential deep ocean mining sites are located around huge sulfide deposits near deep water hydrothermal vents, both active and extinct, as well as around vast areas of polymetallic nodules buried in sediment. Located between 1,400 and 3,700 meters beneath the surface, these untapped mineral reserves are thought to be treasure troves just waiting to be taken advantage of.
Around hydrothermal vents, large areas of sulfide deposits exist containing precious metals including gold, silver, copper, and others. Researchers have estimated that a single deposit could weigh as much as ten million tons, and it is also known that many of these deposits contain exceptionally pure concentrations of coveted precious metals. Nicknamed “SMS” or Seafloor Massive Sulphide systems, these deposits have piqued the interest of nations which are running out of natural resources.
Polymetallic nodules have been gathered in small quantities in the past; these are also known as manganese nodules, and scientists estimate that they take around one million years to grow a single centimeter. Formed of concentric layers of manganese hydroxides and iron around a debris core – sometimes the cores are little crystals, sometimes they are pieces of debris, and sometimes they are recognizable fossilized remains such as sharks teeth and little shells.
Shortly after the concept of deep sea mining was first presented during the mid-1960’s several nations, including the United States, Germany, and France sent research vessels to investigate, and in the years leading to the ultimate abandonment of the idea in 1984, these nations spent around $650 million USD with little to no return.
Modernized techniques promise to change that; and, investors are listening. In order to access these minerals, deep sea mining operators plan to use existing technology adapted from the offshore oil and gas industry, such as remotely operated underwater vehicles and hydraulic pumps to gather ore from the seabed and bring it to the surface, where it will be pumped as a slurry onto production support ships, with water removal taking place onboard a floating production system. After that, it will be carried to cargo barges for stockpiling, after which it will be transported via bulk carrier to a treatment plant for processing with subsequent delivery to end users.
Regulations and Environmental Impacts
Despite the fact that companies proposing new deep sea mining projects have made plans to limit the environmental impact of their operations, and in spite of the fact that proposed projects must follow regulations set forth by ISA, the International Seabed Authority, concerns regarding the potential for disaster persist. The United Nations Conventions on the Law of the Sea set forth a number of regulations between the years of 1973 and 1982 while prospecting was initially underway; those regulations were finally enacted in 1994. Under these regulations, environmental impact assessments must be conducted prior to activities taking place, and various permits must be obtained.
While most new plans point toward accessing precious metals near hydrothermal vents, there is some interest in phosphorus nodule mining due to the current trend toward agricultural use of phosphor-based artificial fertilizers. This in itself is of concern, since phosphorus runoff from these fertilizers contributes to pollution that runs downstream and ends up back in the ocean, uncontained. When water contains too much phosphorus, excess algal blooms occur, depriving fish of oxygen and causing other organisms to die off. Long-term ingestion can lead to toxicity and death in humans and animals alike. Adding more phosphorous to the already overburdened ecosystem is a recipe for disaster; fortunately, no real plans for this type of mining are currently in place.
Because plans are still underway for the first new deep sea mining operation, slated to begin copper and gold production in 2012 through 2014 beneath 1600 meters of water in the Bismarck Sea in Papua New Guinea’s New Ireland Province, the exact environmental impact of this type of project is still unknown. However, experts have surmised that removing part of the ocean floor could result in possible short term toxicity of the water column simply from the disturbance of the benthic layer.
In addition, spills could alter the chemical makeup of the seabed in areas where mining takes place, and sediment plumes from tailings could have a severe impact. Tailings are the fine particles that result from ore processing; while they ultimately end up as sediment, they are often lightweight and can remain suspended in water for quite some time. There are two different types of sediment plumes that are expected to result from deep sea mining operations – surface plumes that could spread over a large area, and near-bottom plumes that could potentially cause problems for filter-feeding benthic organisms when tailings are pumped back down to the mining site. Of the two, surface plumes are most worrisome, as their ability to spread could block light needed for zooplankton survival, affecting the viability of an area’s food web all the way up the food chain.
Fortunately, the first deep sea mining project planned is being undertaken with great care, over an area only about 120 meters across. There is no planned chemical use, and tailings will be pumped back down to the ocean floor where they are not expected to have an adverse effect on zooplankton survival. Several notable scientific and research organizations are involved in ensuring environmental hazards are minimized; they include the USA’s Scripps Institute of Oceanography and Woods Hole Oceanographic Institution, Australia’s Charles Darwin University and Canada’s University of Toronto, among others. Benthic organisms will be recolonized once excavation has been completed.
Mineral resources are important, without a doubt and, it is excellent to see that plans so far have been made slowly and carefully; and, it is hoped that balance can be maintained and a new model for mining can be set in place. While this remains to be seen, deep sea mining may be something we all can live with.