By Dr Juliana Segura-Salazar, Research Fellow at The Julius Kruttschnitt Mineral Research Centre, and Professor Daniel M. Franks, Deputy Director – Research at the Sustainable Minerals Institute, The University of Queensland
Recent tailings dam failures are driving big changes in the way some mining companies are handling their waste. Circular economy approaches are encouraging companies to take a fresh look at whether metals ores might be a source of other mineral by-products.
Each and every year the mining industry generates more than 13 billion tonnes of tailings waste and many billions more of waste rock. That’s more than one tonne of tailings, per person, per year. As the quality of mineral ores decline, more material is being mined for less product and dramatic increases in mining for the renewable energy transition are only going to add to the problem.¹
Tailings are the ground-up rock leftover after mineral processing, and they have long been a major environmental and safety challenge. Tailings are typically stored in a tailings dam, with around 3,400 active tailing storage facilities in the world and the total number of active, inactive and closed facilities estimated at more than eight thousand.²
Recent tailings facility failures have caused many to question whether the disposal of vast volumes of ground-up rock is a responsible practice, and forced them to take a second look at the material that they are disposing.
The Brumadinho legacy
It was a little after noon on Friday 25 January 2019. Hundreds of workers sat at the canteen of Vale’s Córrego do Feijão iron ore mine, nine kilometres northeast of the town of Brumadinho, in the state of Minas Gerais, Brazil.
A loud crack shot through the air.
In less than ten seconds the slope of Tailings Dam 1 at the mine collapsed and in less than five minutes, 9.7 million cubic meters of ground-up rock had flowed out of the dam. The rock, although a solid, behaved like a liquid and flowed downstream at high speed.
The mud flow rapidly travelled through the mine’s canteen and made it all the way to the Paraopeba River, leaving a trail of destruction in its wake; offices, houses, farms, inns, bridges, roads, environments, communities, and lives, all devastated.
270 people perished on that Friday afternoon. And for Vale’s Córrego do Feijão workforce, losing so many colleagues was a devastating experience and an urgent call to action to instigate better waste management practices.
Following Brumadinho’s tragedy, the Brazilian government banned new upstream tailings storage facilities and mandated that old facilities – like the one that collapsed at the Córrego do Feijão mine – be decommissioned by 2021.³
This gave a small team within Vale, who had already been trialling methods to reduce tailings production, new impetus to revolutionise their processes and take their innovations to new heights.
One of such initiatives was the Quartz Project, developed by Dr Emile Scheepers while pursuing his Executive MBA in 2013.
Dr Scheepers’ innovation consisted of taking advantage of the silica-rich material typically discarded with tailings and converting it into an engineered stone capable of performing as a substitute for granite and marble.⁴ What was once merely a promising idea on paper, now became the seed for pioneering circular economy approaches.
Vale invested more than 50 million Brazilian reais (just under AU$15 million) in research and innovation and established partnerships with a wide range of research and development organisations to find circular economy solutions that target a wider variety of minerals in iron ore mining, and minimise the production of waste. The University of Queensland, University of Geneva and Federal University of Minas Gerais, were amongst the research groups that worked with Vale on this challenge.⁵
A by-products team was established, and they developed an innovative processing route with additional stages (concentration, classification, filtration) to co-produce a novel material alongside the primary iron ore concentrate at the Brucutu iron ore mine.
Ore-sand: a novel material
The material is a new type of manufactured sand, called ore-sand⁵, that can function as a substitute for conventional sand in various applications.
In 2020, Vale received its first environmental licence to become an ore-sand producer. In 2021 Vale produced around 250,000 tonnes of sand, which was supplied for sale or donation in construction applications. Vale quadrupled its ore-sand production in 2022 and expects to reach a production of around 2 million tonnes of ore-sand in 2023.
More recently, Vale has expanded this circular economy solution to other operations such as its Viga mine, also located in Minas Gerais, Brazil.⁶
While ore-sand production is undoubtedly influenced by the available infrastructure for transportation to markets, its potential extends far beyond Brazil and can be co-produced from other mineral commodities, such as copper ores.
Ore-sand not only drastically helps to reduce the risks of conventional mine waste management but can also be a competitive option to conventional sand and thus contributes to alleviating the damage caused by the excessive extraction of sand from rivers and sensitive coastal environments.
Unsustainable sand supply and linear tailings management: two global crises
Minerals are fundamental to shaping the world as it is known today, but the traditional methods of mining are resulting in irreparable damage to people and the planet.
The world’s hunger for sand and coarse aggregates has surged threefold in the last two decades, fuelled by changing consumption patterns, rapid urbanisation, and a burgeoning population.
Sand, gravel and crushed stone (collectively known as aggregates) are the second-most extracted and traded resources by volume, after water, and are integral to an array of countless applications, from constructing homes and bridges, to filtering water.
The truth is, however, that the appetite and demand for these fundamental materials comes at a staggering cost to the planet.
Much of the sand and coarse aggregates in use today comes from unsustainable extraction practices in sensitive areas that inflict irreparable damage to vulnerable ecosystems across many regions. Even though there are alternative sources of aggregates such as construction and demolition waste or slag, these do not satisfy the overall demand, making sand extraction from nature an inescapable reality.
Every year, a staggering 50 billion tonnes of fine and coarse aggregates are extracted from quarries, rivers, and other environments, according to the United Nations Environment Programme.⁷
On the other hand, metal mining produces tens of billion tonnes of waste materials per year.
If current linear production patterns persist, the global production of mining waste (predominantly waste rock and tailings) associated with key commodities needed for the clean energy transition, such as copper, nickel, lithium, and manganese, will grow exponentially in the next three decades and may be in the order of 2 trillion tonnes.
It’s time to adopt more sustainable, circular, resource efficient, and responsible practices.
Ore-sand and circular mining – the way forward
When it comes to the circular economy, many in the mining industry frequently relate this concept to the repurposing of waste materials generated within the traditional ‘take-make-usedispose’ model that prevails in the sector. While end-of-pipe solutions may be a necessary way to tackle the risks posed by waste, it must also be acknowledged that this material is rarely fit for other purposes and the public is understandably cautious about using the discards of the mining industry as products.
The industry must take more responsibility for the waste it generates and strive to innovate across all aspects of its operations – from processes and products to business models, policies, and standards.
The key to mining ores more sustainably is innovation.
By implementing practices to reduce waste generation at the source with more efficient extraction and processing technologies, the industry can unlock the full potential of the circular economy.
One solution to reduce mine waste is the generation of byproducts or co-products, such as ore-sand, in mineral processing circuits. This approach involves rethinking processes to prevent mine waste production by proactively redirecting silicate-rich (and other) minerals away from waste rock piles or tailings dams.
In a study published in 2022,⁵ researchers from The University of Queensland and University of Geneva investigated Vale’s by-product innovations and investigated whether the wider application of ore-sand could be a game-changer for the industry.
While transportation of construction by-products to markets is a crucial factor to consider, the researchers found that ore-sand could be used as a substitute for construction and industrial sand.
By mapping mining locations worldwide and modelling global and consumption, the researchers found that nearly a third of mine sites could satisfy some demand for ore-sand within a 50km range. Moreover, almost half of the global sand market (by volume) could potentially have access to a local source of ore-sand.
Plenty of room exists to bring circular economy solutions based on ore-sand co-production to other mines, mineral commodities, and regions.
The research team at The University of Queensland has been working collaboratively with other mining companies.
Newcrest Mining Limited is evaluating the potential for coproducing ore-sand at their Cadia East copper-gold ore operation in New South Wales, Australia from the sandy reject of their HydroFloat cell. This technology has proven beneficial in reducing energy consumption during comminution and improving gold and copper recovery in coarser size fractions compared with conventional flotation equipment. Moreover, the HydroFloat technology offers an unexpected benefit: the recovery of coarser silica-rich material that can become an ore-sand.
The recent study⁸ concluded that this material could be a suitable substitute for fine aggregates in construction applications, opening up a world of possibilities for sustainable building solutions. Studies are progressing towards testing this material’s potential application in concreting and expanding the concept to other mines in Australia and worldwide.
There is still so much potential to unlock, and the team is excited to be at the forefront of this innovative movement to drive transformative change for a more sustainable future.
Footnotes:
- https://doi.org/10.1016/j.resconrec.2022.106859Valenta, R.K., Lèbre, É., Antonio, C., Franks, D.M., Jokovic, V., Micklethwaite, S., Parbhakar-Fox, A., Runge, K., Savinova, E., Segura-Salazar, J., Stringer, M., Verster, I. and Yahyaei, M., 2023. Decarbonisation to drive dramatic increase in mining waste–Options for reduction. Resources, Conservation and Recycling, 190, 106859.
- Franks, D.M., Stringer, M., Torres-Cruz, L.A., Baker, E., Valenta, R., Thygesen, K., Matthews, A., Howchin, J. and Barrie, S., 2021. Tailings facility disclosures reveal stability risks. Scientific reports, 11(1), 5353. https://www.nature.com/articles/s41598-021-84897-0
- Reuters, 18 February 2019. Brazil bans upstream mining dams after deadly Vale disaster. https://www.reuters.com/article/us-vale-sa-disaster-idUSKCN1Q718C
- Mining Magazine, 30 May 2022. Vale on its ‘ore-sands’ revolution. https://www.miningmagazine.com/sustainability/news/1433168/vale-on-its-%E2%80%98ore-sands%E2%80%99-revolution
- Golev, A., Gallagher, L., Vander Velpen, A., Lynggaard, J.R., Friot, D., Stringer, M., Chuah, S., Arbelaez-Ruiz, D., Mazzinghy, D., Moura, L., Peduzzi, P. and Franks, D.M., 2022. Ore-sand: A potential new solution to the mine tailings and global sand sustainability crises. The University of Queensland: Brisbane, QLD, Australia. https://smi.uq.edu.au/files/83107/FinalReport_OreSand_v1.pdf
- International Mining, August 17 2022. Vale brings second Sustainable Sand operation online. https://im-mining.com/2022/08/17/vale-brings-second-sustainable-sand-operation-online/
- United Nations Environment Programme, 2019. Sand and Sustainability: Finding New Solutions for Environmental Governance of Global Sand Resources. https://wedocs.unep.org/20.500.11822/28163
- Segura-Salazar, J. and Franks, D. M., 2023. Ore-sand co-production from Newcrest’s Cadia East HydroFloat Reject: an exploratory study. The University of Queensland: Brisbane, QLD, Australia. https://doi.org/10.14264/96249f6
