The role of mine waste in resourcing decarbonisation and the circular economy

2022 should be known as the year of the critical metal. As the urgency for new technologies to facilitate the transition to a low-carbon future continues, finding these metals is becoming a top priority for the mining sector. 

By Anita Parbhakar-Fox, Sustainable Minerals Institute, the University of Queensland

Just last month, the 2023 Ernst & Young (EY) ‘Top 10 business risks and opportunities for mining and metals’ report identified climate change as the number three risk, reflecting the need to manage emissions and provide the metals needed to make critical change (Figure 1).

The reality: resourcing the energy transition at today’s pace of mining will not suffice. For example, by 2050, we will need at least nine times more copper – in part to power our global communities’ dreams of electric vehicles (EVs). India – which next year will become the planet’s most populated country – has set a 2030 target for EVs to constitute 30 per cent of private cars, 70 per cent of commercial cars, 40 per cent of buses, and 80 per cent of two- and three-wheelers. In the United States, the number of EVs is projected to reach 26.4 million by 2030, with the United Kingdom currently ahead of the required adoption curve to meet its government’s 2032 EV target. Comparatively, Australia is behind, with EV uptake five times lower than the global average. This has led to the proposed development of the Labor Government’s National Electric Vehicle Strategy. 

Copper is not the only metal required. According to the World Bank, production of lithium, graphite and cobalt could increase by as much as 500 per cent by 2050 to meet projected needs.

Change in Australia’s mining sector is coming. But one thing is for certain: increased mining means increased energy and water consumption. New approaches and technologies are being developed to address this, including greater reliance on renewable energy. For example, at Gold Fields’ Agnew gold mine, wind turbines have been installed as part of a new microgrid. Down in Tasmania, the minerals sector boasts that it’s not just the trees that are green, with TMEC’s Ray Mostogl declaring that the state’s mining sector has had net zero emissions for six of the past seven years thanks to hydropower and wind.

Experts warn of serious global water shortages coinciding with climate change, increasing the need for sustainable water usage. Operations are also actively developing ‘closed-loop’ systems to recycle and minimise the draw on fresh water, including the increasing use of membrane technologies.

But while there are plans in place to address these two big-ticket items, what of the colossal volumes of mine waste that are silently accumulating in mega rock dumps or tailings storage facilities? Fly into Mount Isa and you will see that the footprint of the tailings storage facility (TSF) is similar to that of the township itself. To meet 2050 copper demands, experts have calculated that from 2020–50, 858 gross tonnages of tailings and waste rock will be produced. These materials will require adequate management. But with the industry’s TSF management reputation tarnished by major failures at Mount Polley (2014), Samarco (2015), Brumadinho (2019) and, most recently, Jagersfontein (2022), what confidence is there that we are going to be able to adequately manage future waste? The Global Industry Standard on Tailings Management brings renewed hope that, geotechnically speaking, the risk of future TSF failures will be minimised. 

But what of acid and metalliferous drainage (AMD), which is caused by sulphide mineral oxidation? The UN once stated that AMD management was the second-biggest environmental challenge after climate change. Notably, no equivalent global management standard has been developed to curtail AMD formation.

Unsurprisingly, the EY 2023 risks and opportunities report sees environmental, social and governance (ESG) in the number one risk spot. Some argue that mine waste management comes under this banner. Broadly speaking, to do better in ESG terms, the industry must also improve mine waste management. Today’s approach, quite simply, will not work. Designing waste rock dumps to minimise AMD formation by the selective placement of potentially acid-forming materials relative to non-acid-forming or neutralising wastes, and/or covering with capping materials, is not a long-term solution, considering the increased volumes requiring management. Finding new sites to build large TSFs will not work, as protests by the Bob Brown Foundation against a proposed new TSF in Tasmania have shown. Developing new business models (number 10 in the 2023 EY report) could be a game changer. Cue the circular economy.

Australia has ambitions to grow the circular economy. Focusing solely on food, transport and the built environment, circular economy adoption could create an economic benefit of $23 billion in GDP by 2025, with a national target of 80 per cent waste recovery by 2030; however, governmental focus is on glass, plastic, tyres, paper, cardboard, e-waste, food, batteries… what about mining waste? It’s undoubtedly Australia’s biggest waste stream, and yet it’s largely absent from the government’s focus on circularity.

This is a missed opportunity. Critical minerals are often co-located with other minerals of economic interest. Therefore, there is high potential for mine waste to be well endowed in commodities such as cobalt, lithium, rare earth elements and indium. These ‘anthropogenic deposits’ represent valuable resources to supplement future needs and, if (re)processed, offer a real AMD management solution as (acid forming) sulphides commonly host critical metals. 

Where should critical mineral explorers be looking? Australia reportedly has 50,000 abandoned sites containing mine waste. The secondary resources target map has already been drawn, as state governments have identified their location (Figure 2).

In Australia, companies like EQ Resources and Dover Castle Metals have already been exploring for, and recovering, critical metals from mine waste; however, there has been a big push by governments to explore and stimulate investor interest in Australia’s untapped future resources. The first cab off the rank was the Queensland State Government, which in 2020 commissioned a four-year program to explore critical metals in mine waste across the state. Two years into the program, the Sustainable Minerals Institute (SMI) has identified several prospective areas for cobalt, rare earth elements, tungsten and indium. The Institute has identified that in North West Queensland’s tailings, there are approximately 158,720 tonnes of cobalt present. Based on today’s market price, this could equate to a value of at least $8 billion (Figure 3).

These studies are already attracting overseas investors. For example, a new partnership between the Queensland Government, SMI and the Japan Oil, Gas and Metals National Corporation has been established to assess tailings at the Rocklands Mine (Figure 4). Additional sites across Australia are also being examined, funded by Geoscience Australia and the Northern Territory, South Australian and New South Wales governments. 

The prospect of transforming abandoned and legacy mines into vital resources for decarbonisation is becoming real. The next challenge will be resource recovery from these complex ore bodies. While the Morrison Government committed $240 million to developing critical mineral processing facilities, their technical scope should also aim to test secondary ore feedstocks. Finally, to be truly circular, METS companies should seek to valorise new waste that is generated.

Ultimately, Australia has an opportunity to grow the critical mineral and circular economy sectors while simultaneously reducing environmental risks, and providing much-needed resources for decarbonisation. Secondary resources play a key role in our greener future. 

Associate Professor Anita Parbhakar-Fox is Leader of the Mine Waste Transformation through Characterisation Group at the Sustainable Minerals Institute, The University of Queensland (a.parbhakarfox@uq.edu.au).

Reference

Werner TT, Bach PM, Yellishetty M, Amirpoorsaeed F, Walsh S, Miller A, Roach M, Schnapp A, Solly P, Tan Y, Lewis C, Hudson E, Heberling K, Richards T, Chia HC, Truong M, Gupta T, Wu X. ‘A Geospatial Database for Effective Mine Rehabilitation in Australia.’ Minerals. 2020; 10(9):745. https://doi.org/10.3390/min10090745

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