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mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic via ...
, tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (
gangue In mining, gangue () is the commercially worthless material that surrounds, or is closely mixed with, a wanted mineral in an ore deposit. It is thus distinct from overburden, which is the waste rock or materials overlying an ore or mineral body t ...
) of an
ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
. Tailings are different to
overburden In mining, overburden (also called waste or spoil) is the material that lies above an area that lends itself to economical exploitation, such as the rock, soil, and ecosystem that lies above a coal seam or ore body. Overburden is distinct from tai ...
, which is the waste rock or other material that overlies an ore or mineral body and is displaced during mining without being processed. The extraction of minerals from ore can be done two ways:
placer mining Placer mining () is the mining of stream bed (Alluvium, alluvial) deposits for minerals. This may be done by open-pit mining, open-pit (also called open-cast mining) or by various surface excavating equipment or tunneling equipment. Placer minin ...
, which uses water and gravity to concentrate the valuable minerals, or
hard rock mining Underground hard-rock mining refers to various underground mining techniques used to excavate "hard" minerals, usually those containing metals, such as ore containing gold, silver, iron, copper, zinc, nickel, tin, and lead. It also involves the ...
, which pulverizes the rock containing the ore and then relies on chemical reactions to concentrate the sought-after material. In the latter, the extraction of minerals from ore requires
comminution Comminution is the reduction of solid materials from one average particle size to a smaller average particle size, by crushing, grinding, cutting, vibrating, or other processes. In geology, it occurs naturally during faulting in the upper part of ...
, i.e., grinding the ore into fine particles to facilitate extraction of the target element(s). Because of this comminution, tailings consist of a
slurry A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pu ...
of fine particles, ranging from the size of a grain of sand to a few micrometres. Mine tailings are usually produced from the
mill Mill may refer to: Science and technology * * Mill (grinding) * Milling (machining) * Millwork * Textile mill * Steel mill, a factory for the manufacture of steel * List of types of mill * Mill, the arithmetic unit of the Analytical Engine early ...
in slurry form, which is a mixture of fine mineral particles and water. Tailings can be dangerous sources of toxic chemicals such as
heavy metals upright=1.2, Crystals of osmium, a heavy metal nearly twice as dense as lead">lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals are generally defined as ...
,
sulfide Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...
s and
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
content. These chemicals are especially dangerous when stored in water in ponds behind
tailings dams In mining, tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different to overburden, which is the waste rock or other material that overlie ...
. ite?/sup> These ponds are also vulnerable to major breaches or leaks from the dams, causing environmental disasters. Because of these and other environmental concerns such as groundwater leakage, toxic emissions and bird death, tailing piles and ponds are often under regulatory scrutiny. There are a wide range of methods for recovering economic value, containing or otherwise mitigating the impacts of tailings. However, internationally, these practices are poor, sometimes violating human rights. To mitigate risks of harm, the first UN-level standard for tailing management was established 2020.


Terminology

Tailings are also called mine dumps, culm dumps, slimes, tails, refuse, leach residue, slickens, or terra-cone (terrikon).


Examples


Sulfide minerals

The effluent from the tailings from the mining of sulfidic minerals has been described as "the largest environmental liability of the mining industry". These tailings contain large amounts of
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
(FeS2) and
Iron(II) sulfide Iron(II) sulfide or ferrous sulfide (Br.E. sulphide) is one of a family chemical compounds and minerals with the approximate formula . Iron sulfides are often iron-deficient non-stoichiometric. All are black, water-insoluble solids. Preparatio ...
(FeS), which are rejected from the sought-after ores of copper and nickel, as well as coal. Although harmless underground, these minerals are reactive toward air in the presence of microorganisms, which if not properly managed lead to
acid mine drainage Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines or coal mines. Acid rock drainage occurs naturally within some environments as part of the rock weathering ...
.


Phosphate rock mining

Between 100 million and 280 million tons of
phosphogypsum Phosphogypsum (PG) is the calcium sulfate hydrate formed as a by-product of the production of fertilizer from phosphate rock. It is mainly composed of gypsum (CaSO4·2H2O). Although gypsum is a widely used material in the construction industry, ...
waste are estimated to be produced annually as a consequence of the processing of
phosphate rock Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock that contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4% to 20% phosphorus pentoxi ...
for the production of phosphate fertilizers. In addition to being useless and abundant, phosphogypsum is radioactive due to the presence of naturally occurring
uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
and
thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...
, and their
daughter isotope In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps ( ...
s. Depending on the price achievable on the
uranium market The uranium market, like all commodity markets, has a history of volatility, moving with the standard forces of supply and demand as well as geopolitical pressures. It has also evolved particularities of its own in response to the unique nature and ...
, extraction of the uranium content may be economically lucrative even absent other incentives, such as reducing the harm the radioactive heavy metals do to the environment.


Aluminium

Bauxite tailings Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO( ...
is a waste product generated in the industrial production of
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
. Making provision for the approximately 77 million tons that is produced annually is one of the most significant problems for the aluminium mining industry.Ayres, R. U., Holmberg, J., Andersson, B., "Materials and the global environment: Waste mining in the 21st century", MRS Bull. 2001, 26, 477.


Red mud


Coal


Economics

Early mining operations often did not take adequate steps to make tailings areas environmentally safe after closure. Modern mines, particularly those in jurisdictions with well-developed mining regulations and those operated by
responsible mining Responsible mining is commonly defined as mining that involves and respects all stakeholders, minimizes and takes account of its environmental impact, and prioritizes a fair division of economic and financial benefits. There is a strong focus on sta ...
companies, often include the rehabilitation and proper closure of tailings areas in their costs and activities. For example, the Province of
Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...
, Canada, requires not only the submission of a closure plan before the start of mining activity, but also the deposit of a financial guarantee equal to 100% of the estimated rehabilitation costs. Tailings dams are often the most significant environmental liability for a mining project.TE Martin, MP Davies. (2000)
Trends in the stewardship of tailings dams
Mine tailings may have economic value in
carbon sequestration Carbon sequestration is the process of storing carbon in a carbon pool. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in land ...
due to the large exposed surface area of the minerals.


Environmental concerns

The fraction of tailings to ore can range from 90–98% for some copper ores to 20–50% of the other (less valuable) minerals. The rejected minerals and rocks liberated through mining and processing have the potential to damage the environment by releasing toxic metals (arsenic and mercury being two major culprits), by acid drainage (usually by microbial action on sulfide ores), or by damaging aquatic wildlife that rely on clear water (vs suspensions).Franks, DM, Boger, DV, Côte, CM, Mulligan, DR. 2011. Sustainable Development Principles for the Disposal of Mining and Mineral Processing Wastes. Resources Policy. Vol. 36. No. 2. pp 114–122 Tailings ponds can also be a source of
acid drainage Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mining, mines or Coal mining, coal mines. Acid rock drainage occurs naturally within some environments as part of ...
, leading to the need for permanent monitoring and treatment of water passing through the tailings dam; the cost of mine cleanup has typically been 10 times that of mining industry estimates when acid drainage was involved.


Disasters

The greatest danger of tailings ponds is dam failure, with the most publicized failure in the U.S. being the failure of a coal slurry dam in the
West Virginia West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the Bur ...
Buffalo Creek Flood of 1972, which killed 125 people; other collapses include the
Ok Tedi environmental disaster The Ok Tedi environmental disaster caused severe harm to the environment along of the Ok Tedi River and the Fly River in the Western Province of Papua New Guinea between around 1984 and 2013. The lives of 50,000 people have been disrupted. One ...
in
New Guinea New Guinea (; Hiri Motu Hiri Motu, also known as Police Motu, Pidgin Motu, or just Hiri, is a language of Papua New Guinea, which is spoken in surrounding areas of Port Moresby (Capital of Papua New Guinea). It is a simplified version of ...
, which destroyed the fishery of the
Ok Tedi River The Ok Tedi is a river in New Guinea. The Ok Tedi Mine is located near the headwaters of the river, which is sourced in the Star Mountains. It is the second largest tributary of the Fly River. Nearly the entirety of the river runs through the N ...
. On average, worldwide, there is one big accident involving a tailings dam each year., page 452–458 Other disasters caused by tailings dam failures are, the 2000 Baia Mare cyanide spill and the Ajka alumina plant accident.


Human rights

Tailings deposits tend to be located in rural areas or near marginalized communities, such as
indigenous communities Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...
. The Global Industry Standard on Tailings Management recommends that "a human rights due diligence process is required to identify and address those that are most at risk from a tailings facility or its potential failure."


Storage methods

Historically, tailings were disposed of in the most convenient manner, such as in downstream running water or down drains. Because of concerns about these sediments in the water and other issues, tailings ponds came into use. The sustainability challenge in the management of tailings and waste rock is to dispose of material, such that it is inert or, if not, stable and contained, to minimise water and energy inputs and the surface footprint of wastes and to move toward finding alternate uses.


Tailings dams and ponds

Bounded by impoundments (an impoundment is a dam), these dams typically use "local materials" including the tailings themselves, and may be considered
embankment dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface and ...
s. Traditionally, the only option for tailings storage was to deal with a tailings slurry. This slurry is a dilute stream of the tailings solids within water that was sent to the tailings storage area. The modern tailings designer has a range of tailings products to choose from depending upon how much water is removed from the slurry prior to discharge. The removal of water not only can create a better storage system in some cases (e.g. dry stacking, see below) but can also assist in water recovery which is a major issue as many mines are in arid regions. In a 1994 description of tailings impoundments, however, the U.S. EPA stated that dewatering methods may be prohibitively expensive except in special circumstances. Subaqueous storage of tailings has also been used. Tailing ponds are areas of refused
mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic via ...
tailings where the waterborne refuse material is pumped into a
pond A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from th ...
to allow the
sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...
(meaning separation) of solids from the water. The pond is generally impounded with a dam, and known as tailings impoundments or tailings dams.US EPA. (1994)
Technical Report: Design and Evaluation of Tailings Dams
.
It was estimated in 2000 that there were about 3,500 active tailings impoundments in the world. The ponded water is of some benefit as it minimizes fine tailings from being transported by wind into populated areas where the toxic chemicals could be potentially hazardous to human health; however, it is also harmful to the environment. Tailing ponds are often somewhat dangerous because they attract wildlife such as waterfowl or caribou as they appear to be a natural pond, but they can be highly toxic and harmful to the health of these animals. Tailings ponds are used to store the waste made from separating minerals from rocks, or the slurry produced from tar sands mining. Tailings are sometimes mixed with other materials such as
bentonite Bentonite () is an absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite. Na-montmorillonite has a considerably greater swelling capacity than Ca-mon ...
to form a thicker slurry that slows the release of impacted water to the environment. There are many different subsets of this method, including valley impoundments, ring dikes, in-pit impoundments, and specially dug pits. The most common is the valley pond, which takes advantage of the natural topographical depression in the ground. Large earthen dams may be constructed and then filled with the tailings. Exhausted open pit mines may be refilled with tailings. In all instances, due consideration must be made to contamination of the underlying water table, amongst other issues. Dewatering is an important part of pond storage, as the tailings are added to the storage facility the water is removed – usually by draining into decant tower structures. The water removed can thus be reused in the processing cycle. Once a storage facility is filled and completed, the surface can be covered with topsoil and revegetation commenced. However, unless a non-permeable capping method is used, water that infiltrates into the storage facility will have to be continually pumped out into the future.


Paste tailings

Paste tailings is a modification to the conventional methods of disposal of tailings (pond storage). Conventional tailings slurries are composed of a low percent of solids and relatively high water content (normally ranging from 20% to 60% solids for most hard rock mining) and when deposited into the tailings pond the solids and liquids separate. In paste tailings the percent of solids in the tailings slurry is increased through the use of paste thickeners to produce a product where the minimal separation of water and solids occurs and the material is deposited into a storage area as a paste (with a consistency somewhat like toothpaste). Paste tailings has the advantage that more water is recycled in the processing plant and therefore the process is more water efficient than conventional tailings and there is a lower potential for seepage. However the cost of the thickening is generally higher than for conventional tailings and the pumping costs for the paste are also normally higher than for conventional tailings as positive displacement pumps are normally required to transport the tailings from the processing plant to the storage area. Paste tailings are used in several locations around the world including Sunrise Dam in Western Australia and Bulyanhulu Gold Mine in Tanzania.


Dry stacking

Tailings do not have to be stored in ponds or sent as slurries into oceans, rivers or streams. There is a growing use of the practice of dewatering tailings using vacuum or pressure filters so the tailings can then be stacked. This saves water which potentially reduces the impacts on the environment in terms of a reduction in the potential seepage rates, space used, leaves the tailings in a dense and stable arrangement and eliminates the long-term liability that ponds leave after mining is finished. However although there are potential merits to dry stacked tailings these systems are often cost prohibitive due to increased capital cost to purchase and install the filter systems and the increase in operating costs (generally associated electricity consumption and consumables such as filter cloth) of such systems.


Storage in underground workings

While disposal into exhausted open pits is generally a straightforward operation, disposal into underground voids is more complex. A common modern approach is to mix a certain quantity of tailings with waste aggregate and cement, creating a product that can be used to backfill underground voids and stopes. A common term for this is HDPF – High Density Paste Fill. HDPF is a more expensive method of tailings disposal than pond storage, however it has many other benefits – not just environmental but it can significantly increase the stability of underground excavations by providing a means for ground stress to be transmitted across voids – rather than having to pass around them – which can cause mining induced seismic events like that suffered previously at the Beaconsfield Mine Disaster.


Riverine tailings

Usually called RTD – Riverine Tailings Disposal. In most environments, not a particularly environmentally sound practice, it has seen significant utilisation in the past, leading to such spectacular environmental damage as done by the
Mount Lyell Mining and Railway Company Mount Lyell Mining and Railway Company was a Tasmanian mining company formed on 29 March 1893, most commonly referred to as ''Mount Lyell''. Mount Lyell was the dominant copper mining company of the West Coast from 1893 to 1994, and was based in ...
in
Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...
to the King River, or the poisoning from the
Panguna Panguna is a town and a (now decommissioned) copper mine on Bougainville Island, Papua New Guinea. It was owned and operated by Bougainville Copper Ltd, a subsidiary of Rio Tinto. Beginning operations in 1972, the company hired thousands of wor ...
mine on
Bougainville Island Bougainville Island (Tok Pisin: ''Bogenvil'') is the main island of the Autonomous Region of Bougainville, which is part of Papua New Guinea. It was previously the main landmass in the German Empire-associated North Solomons. Its land area is ...
, which led to large-scale civil unrest on the island, and the eventual permanent closing of the mine. As of 2005, only three mines operated by international companies continued to use river disposal: The
Ok Tedi mine The Ok Tedi Mine is an open-pit copper and gold mine in Papua New Guinea located near the headwaters of the Ok Tedi River, in the Star Mountains Rural LLG of the North Fly District of the Western Province of Papua New Guinea. The mine is oper ...
, the
Grasberg mine The Grasberg mine has one of the largest gold mining, reserves of gold and copper extraction, copper in the world. It is located in Mimika Regency, Central Papua, Indonesia near Puncak Jaya. It is operated by PT Freeport Indonesia (PTFI, ''s ...
and the
Porgera mine The Porgera Gold Mine is a large gold and silver mining operation in near Porgera, Enga Province, Papua New Guinea, Enga province, Papua New Guinea (PNG), located at the head of the Porgera Valley. The mine is situated in the rain forest covered h ...
, all on New Guinea. This method is used in these cases due to seismic activity and landslide dangers which make other disposal methods impractical and dangerous.


Submarine tailings

Commonly referred to as STD (Submarine Tailings Disposal) or DSTD (Deep Sea Tailings Disposal). Tailings can be conveyed using a pipeline then discharged so as to eventually descend into the depths. Practically, it is not an ideal method, as the close proximity to off-shelf depths is rare. When STD is used, the depth of discharge is often what would be considered shallow, and extensive damage to the seafloor can result due to covering by the tailings product. It is also critical to control the density and temperature of the tailings product, to prevent it from travelling long distances, or even floating to the surface. This method is used by the gold mine on
Lihir Island Lihir Island (a.k.a. Niolam Island) is the largest island in the Lihir group of islands, 22 km long and 14.5 km wide, in Papua New Guinea's New Ireland Province. It consists of a complex of several overlapping basaltic stratovolcanoes r ...
; its waste disposal has been viewed by environmentalists as highly damaging, while the owners claim that it is not harmful.


Phytostabilisation

Phytostabilisation is a form of
phytoremediation Phytoremediation technologies use living plants to clean up soil, air and water contaminated with hazardous contaminants. It is defined as "the use of green plants and the associated microorganisms, along with proper soil amendments and agronomi ...
that uses hyperaccumulator plants for long-term stabilisation and containment of tailings, by sequestering pollutants in soil near the roots. The plant's presence can reduce wind erosion, or the plant's roots can prevent water erosion, immobilise metals by adsorption or accumulation, and provide a zone around the roots where the metals can precipitate and stabilise. Pollutants become less bioavailable and livestock, wildlife, and human exposure is reduced. This approach can be especially useful in dry environments, which are subject to wind and water dispersion.


Different methods

Considerable effort and research continues to be made into discovering and refining better methods of tailings disposal. Research at the Porgera Gold Mine is focusing on developing a method of combining tailings products with coarse waste rock and waste muds to create a product that can be stored on the surface in generic-looking waste dumps or stockpiles. This would allow the current use of riverine disposal to cease. Considerable work remains to be done. However, co-disposal has been successfully implemented by several designers including
AMEC Amec Foster Wheeler plc was a British multinational consultancy, engineering and project management company headquartered in London, United Kingdom. In October 2017, it was acquired by Wood Group. It was focused on the Oil, Gas & Chemicals, M ...
at, for example, the Elkview Mine in British Columbia.


Pond reclamation by microbiology

During extraction of the oil from oil sand, tailings consisting of water, silt, clays and other solvents are also created. This solid will become mature fine tailings by gravity. Foght ''et al'' (1985) estimated that there are 103 anaerobic
heterotrophs A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
and 104 sulfate-reducing
prokaryotes A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Greek πρό (, 'before') and κάρυον (, 'nut' or 'kernel').Campbell, N. "Biology:Concepts & Connec ...
per milliliter in the tailings pond, based on conventional most probable number methods. Foght set up an experiment with two tailings ponds and an analysis of the
archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
,
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
, and the gas released from tailings ponds showed that those were
methanogens Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They are prokaryotic and belong to the domain Archaea. All known methanogens are members of the archaeal phylum Euryarchaeota. Methanogens are comm ...
. As the depth increased, the moles of CH4 released actually decreased. Siddique (2006, 2007) states that methanogens in the tailings pond live and reproduce by anaerobic degradation, which will lower the molecular weight from
naphtha Naphtha ( or ) is a flammable liquid hydrocarbon mixture. Mixtures labelled ''naphtha'' have been produced from natural gas condensates, petroleum distillates, and the distillation of coal tar and peat. In different industries and regions ''n ...
to
aliphatic In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane, or ...
, aromatic hydrocarbons, carbon dioxide and methane. Those archaea and bacteria can degrade the naphtha, which was considered as waste during the procedure of refining oil. Both of those degraded products are useful. Aliphatic, aromatic hydrocarbons and methane can be used as fuel in the humans' daily lives. In other words, these methanogens improve the coefficient of utilization. Moreover, these methanogens change the structure of the tailings pond and help the pore water efflux to be reused for processing oil sands. Because the archaea and bacteria metabolize and release bubbles within the tailings, the pore water can go through the soil easily. Since they accelerate the densification of mature fine tailings, the tailings ponds are enabled to settle the solids more quickly so that the tailings can be reclaimed earlier. Moreover, the water released from the tailings can be used in the procedure of refining oil. Reducing the demand of water can also protect the environment from drought.


Reprocessing

As mining techniques and the price of minerals improve, it is not unusual for tailings to be reprocessed using new methods, or more thoroughly with old methods, to recover additional minerals. Extensive tailings dumps of
Kalgoorlie Kalgoorlie is a city in the Goldfields–Esperance region of Western Australia, located east-northeast of Perth at the end of the Great Eastern Highway. It is sometimes referred to as Kalgoorlie–Boulder, as the surrounding urban area includ ...
/ Boulder in Western Australia were re-processed profitably in the 1990s by KalTails Mining. A machine called the PET4K Processing Plant has been used in a variety of countries for the past 20 years to remediate contaminated tailings.


International policy

The UN and business communities developed an international standard for tailings management in 2020 after the critical failure of the
Brumadinho dam disaster The Brumadinho dam disaster occurred on 25 January 2019 when Dam I, a tailings dam at the Córrego do Feijão iron ore mine, east of Brumadinho, Minas Gerais, Brazil, suffered a catastrophic failure. The dam is owned by Vale, the same comp ...
. The program was convened by
United Nations Environment Programme The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on th ...
(UNEP),
International Council on Mining and Metals ICMM was founded in 2001, as a CEO-led leadership organization, to improve sustainable development performance in the mining and metals industry. Sustainable Development In late 1998 a small group of mining industry CEOs came together to quest ...
(ICMM) and the
Principles for Responsible Investment Principles for Responsible Investment (UNPRI or PRI) is a United Nations-supported international network of financial institutions working together to implement its six aspirational principles, often referenced as "the Principles". Its goal is to u ...
.


See also

*
Coal slurry impoundment Coal slurry is a mixture of solids (mined coal or coal waste) and liquids (water or organic) produced by a coal preparation plant. Preparation To transform the coal ash into a slurry, coal is separated from non-combustible components and can ...
*
Landfarming Landfarming is an Biotreatment#Ex-situ Bioremediation of Contaminated Soils, ex-situ waste treatment process that is performed in the upper soil zone or in biotreatment cells. Soil contamination, Contaminated soils, sediments, or sludges are transpo ...
*
Mine closure planning {{No footnotes, date=July 2009 Mine closure planning involves planning effectively for the after-mining landscape – all activities required before, during, and after the operating life of a mine that are needed to produce an acceptable landscape ...
*
Mine reclamation Mine reclamation is the process of modifying land that has been mined to ecologically functional or economically usable state. Although the process of mine reclamation occurs once mining is completed, the planning of mine reclamation activiti ...
*
Spoil tip A spoil tip (also called a boney pile, culm bank, gob pile, waste tip or bing) is a pile built of accumulated ''spoil'' – waste material removed during mining. These waste materials are typically composed of shale, as well as smaller quant ...
*
Tailings dam A tailings dam is typically an earth-fill embankment dam used to store byproducts of mining operations after separating the ore from the gangue. Tailings can be liquid, solid, or a slurry of fine particles, and are usually highly toxic and potent ...
* Oil sands tailings ponds


References


External links


Tailings Info site



Submarine Tailings Disposal
at the
Mineral Policy Institute The Mineral Policy Institute is an Australian-based non-governmental organisation that specialises in preventing environmentally and socially destructive mining, minerals and energy projects in Australia, Asia and the Pacific. The institute as form ...

Carbon sequestration in mine tailings
{{Pond Environmental impact of mining Waste Metallurgical processes