Mining is a process that produces vast amounts of material, for which the industry is trying to find a sustainable – and profitable – use. Tailings production is an inherent part of mining and metals processing and will remain so for the foreseeable future.
There is also a serious safety concern inherent in the process, with tailings likely to be a dangerous source of toxic chemicals.
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“I have seen estimates for global tailings production of around 14.5 billion tonnes a year, all of which must be stored safely for a significant amount of time – if not in perpetuity,” Simon Jowitt, director and state geologist of the Nevada Bureau of Mines and Geology, tells Mining Technology.
That amount is also unlikely to decrease at any time soon, “so the continued storage of this […] material, [which] is often challenging to keep safely, remains a major concern for the industry”.
Tailings can contain significant amounts of metals that either were ignored the first time around because of low demand for the metal at the time of mining (or a lack of consideration of potential extraction), or because of poor recovery.
“There are several efforts globally to characterise both legacy tailings (post-mining) and tailings at currently active mines for the extraction of critical and other metals. We are currently doing some of this work in Nevada, and I have also been involved in work assessing the potential of tailings and other mining waste for tellurium and other metal production,” Jowitt adds.
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By GlobalDataThere are other potential uses for tailings from certain mineral deposits, such as carbon dioxide sequestration.
Emma Gagen, director, International Council on Mining and Metals (ICMM), tells Mining Technology that if not managed responsibly, “tailings pose environmental and societal risks”.
However, companies’ robust implementation of the Global Industry Standard on Tailings Management across sites “can help to support continual improvement in the safe, responsible and transparent management of tailings”.
She adds that reducing tailings is an “ambitious challenge that requires an integrated approach across most parts of the mining process”.
The ICMM published a Tailings Reduction Roadmap in 2022 to provide strategic direction to the mining and metals industry on how to accelerate the development and adoption of some of the most promising technologies to reduce tailings – including approaches such as reusing existing tailings for new purposes and products. This helps to reduce the volume being stored whilst creating additional value.
Making sand: a process of tailings avoidance
Moving beyond minerals and metals recovery, there are other opportunities to minimise the waste associated with tailings and turning them into something of real commercial use.
In mid-May, a sustainable mining start-up – OreSand, led by Professor Daniel Franks of the Sustainable Minerals Institute – backed by University of Queensland (UQ) researchers, was recognised by the World Economic Forum (WEF) for advancing tailings management.
WEF’s Uplink Top Innovators programme named the project has as one of eight global winners that will gain access to networks capable of supporting and scaling it up.
OreSand offers mining companies research-backed data to help them drastically reduce waste, as well as produce useful sand byproducts at a time when global demand for the material is surging, according to statement from UQ.
“Most of the minerals we mine are only a tiny fraction of the millions and millions of tonnes of ore we end up producing as a result. Hence, we end up blasting, crushing and grinding an awful lot of material we don’t actually need or use,” says Franks. The main commodities that contribute to this large amount of material are coal, copper, gold, iron ore, phosphate and zinc.
As the energy transition is metals-intensive, investment in renewable energy, energy storage and electric vehicles will increase demand for critical materials such as copper, cobalt and nickel – which, in turn, will lead to greater production of tailings under current production processes.
“But,” says Franks, “the really in-demand solid material used by humans is sand, and the amount of gravel, crushed stone and sand being used is close to 50 billion tonnes a year. Sand is now becoming a major global sustainability issue, especially when it is extracted from dynamic ecosystems, such as rivers, lakes and the ocean.”
“What we have tried so far is to reuse and repurpose tailings, and it hasn’t worked, for two reasons: tailings are not fit for purpose, and lack the required characteristics of the product; and governments and the general public have been rightly quite wary of using the mining industry’s waste,” adds Franks.
The rise of OreSand
However, Franks points out that processes have been added over the past five years to extract sand as a byproduct of mining – and produce something called OreSand, a type of manufactured sand that can be used in either construction and other industrial processes.
“Technically, this is not tailings repurposing, this a product made from the ore. This is a process that reduces or avoids waste and should really be viewed as a change in perspective,” he adds.
Franks points out that the “major advantage of OreSand from a construction perspective is that you get the crushing and grinding for free, as this was necessary for the primary metal. This also means of course that the sand is a lower-carbon product”.
OreSand can be used as a substitute for construction and industrial sand, and is suitable for applications such as road construction, brickmaking and the manufacture of concrete. OreSand can also be viewed as an integral part of the circular economy as it is a product of the ore itself, not a byproduct of mining waste.
Minimising the impact of tailings
Poorly managed tailings can have significant environmental impacts, says Jowitt: all you need to do is look at events at Brumadinho, Bento Rodrigues, Sino-Metals in Zambia, Jagersfontein, and more, even back to 1966 and Aberfan in Wales (when a colliery spoil tip collapsed, killing 144 people).
“True, recent reassessments, developments and improvement in tailings storage facility design have been made (as a result of high-profile failures), but tailings storage facilities are sometimes built in areas where failures could have extreme consequences,” he adds.
There is a lot of potential to generate wealth from waste, says Jowitt. The concept of not-for-profit mining is actively being discussed, “where revenue from (for example) critical metal extraction from tailings is used to remediate problematic mine sites, as well as developing secure domestic critical metal and mineral supply chains”.
“Obviously, there is likely to be profits made as well, but more Good Samaritan-type legislation may be needed to more fully realise this potential,” says Jowitt.
A spokesperson from Fortescue, a global metal mining company headquartered in Australia, told Mining Technology that the industry is “increasingly collaborating on circular economy initiatives, with growing potential to recover residual minerals from stored tailings or repurpose tailings for other projects”, while the company remains committed to reducing and recycling waste.
