By: Anita Parbhakar-Fox, The University of Queensland’s Sustainable Minerals Institute (SMI).

Abstract

To support the development of greener technologies for the energy transition, resources of critical minerals are required. These include cobalt, tungsten, indium, gallium, germanium, vanadium and a whole range of rare earth elements (REE). 

Traditionally, these metals were considered unwanted by-products of base metal and precious metal mining operations, and consequently are concentrated in mine waste. 

In Australia, a national program is underway to sample mine waste materials to search for these critical metals. Potential new resources of Co have been identified in copper tailings in Queensland, whilst other states show promising results for REE, tungsten, antimony, bismuth and indium. 

Focus now turns to the challenges ahead - having the technologies in place to facilitate economic recovery from these heterogenous materials and creating the right political framework to support this vital contribution to the energy transition. 

Introduction

As a child, I was alarmed by the unescapable doom faced by our solar system. I would torture myself looking at encyclopedia illustrations of our sun running out of hydrogen, entering its red giant phase, and engulfing planet Earth 5 billion years into the future. Though the time scale was unfathomable, I was distraught thinking humanity would be wiped out. 

As a teenager, this preoccupation with the end of time continued, but this time studying the Intergovernmental Panel for Climate Change (IPCC) reports. The graphs were compelling, due to industrialisation and societies moving upwards through Rostow's Stages of Economic Growth, dangerous quantities of greenhouse gases (GHG) were being produced. The result, doom for humanity, but this time on a conceivable timescale. No longer billions of years or even millions, but now centuries or less until utter devastation.  

Fast-forward 30 years, there has been a great deal of talk about designing industry practices and indeed encouraging consumers to make different choices to reduce our GHG emissions to slow climate change. How much action has been taken? How much more is needed? What has really changed since the IPCC started documenting our impacts? Indeed, the Kyoto Protocol, Sustainable Development Goals and the Paris Agreement were significant in encouraging countries to set, and commit, to GHG reduction targets and start transitioning towards a low-carbon future. 

The requirement for this brave new world which, until recently, our governments have arguably been reluctant to embrace, include significant increases in the manufacturing of electrical vehicles and renewable energy technologies. But what does this mean for mining, and more importantly mine waste?  

Role of Mine

Professor Richard Herrington (formerly of the Natural History Museum, London, UK) documented the vital role of mining to support a low-carbon future in Nature (2021). For the geoscience and engineering world this was not news, but for the public, this started a new conversation around the future of mining. However, instead of seeing an uptake of students and new professionals signing up to geology and mining related careers to join the green revolution, the mining sectors image crisis only seems to have deepened. And it isn’t just the local NIMBYs (‘Not in my backyard’) or Extinction Rebellion who oppose mining, the United Nations Secretary-General António Guterres delivered anti-mining sentiments at last years’ COP-26. In October, Birkbeck College, London announced they will not hold relationships of any kind with oil, gas or mining companies. Concerns are valid regarding the impacts mining activities can have, though distinctions between thermal coal and metalliferous mining need to be made. One thing is for certain, the mining sector must commit and deliver on embedding Environmental, Social and Governance or ESG (named as EYs 2023 number 1 Risk in Mining¹) standards commensurate to the global communities’ expectations in order to meet our urgent energy transition needs. 

For example, many studies report that by 2050 we will need at least 9 times more copper helping, in part, to power our global communities’ dreams of electric vehicles (EVs). India, which next year will become the planets most populated country, has set a 2030 target for EVs to constitute 30% of private cars, 70% of commercial cars, 40% of buses and 80% of two and three-wheelers. In the United States, the number of EVs is projected to reach 26.4 million by 2030, and the UK is currently ahead of the required adoption curve to meet the Governments 2032 EV target. However, 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% by 2050 to meet projected needs.

Where are we going to find these future resources? Across commodities, we are mining larger tonnages at lower grade. Are we going to need to get the grades we need by going deeper? And if we go deeper, what are the increased risks in this dynamic climate? Will autonomous mining be the key to de-risking digging deeper and unlocking this opportunity? Alternatively, should we be looking on our seabeds for cobalt and manganese-rich nodules or could vital ecosystems be devastated in ways that have yet to be modelled? Should we be exploring beyond the exosphere and embracing space mining? As an example, Psyche, a potential planetesimal core, whilst 1/16^th the size of the moon, is an asteroid worth US$ 10,000 quadrillion due to its nickel and iron composition. If mineable, then dynamic nickel pricing as observed earlier this year due to the Russia-Ukraine conflict (30% increase in March 2022) would be a thing of the past, with a reliable steady source of metals instead being tapped. Whilst humans are natural explorers keen to explore the next frontier, are we missing the most obvious source of energy transition metals… mine waste?  

At current rates of mining, colossal volumes of mine waste are silently accumulating in mega rock dumps or tailings storage facilities across the world. In Australia, if you fly into Mt Isa you will see that the footprint of the tailings storage facility (TSF) is almost similar to that of the township itself. To meet 2050 copper demands, experts have calculated that 858 Gt of tailings and waste rock will be produced between 2020-2050. These materials will require adequate management. Currently, mine waste is managed by placing materials into purpose-built facilities or dumps (Figure 1). However, associated with these are potential geotechnical and geoenvironmental risks. As the climate evolves towards more extreme weather conditions, these risks will be exacerbated. Drastic changes are required as currently the industry’s TSF management reputation has been tarnished by major failures at Mount Polley (2014), Samarco (2015), Brumadinho (2019) and most recently, Jagerfontein (2022). When we consider the volumes of materials, we will need to mine to feed the energy transition what confidence is there that we are going to be able to adequately manage future waste? The Global Industry Standard on Tailings management²  brings renewed hope that geotechnically speaking, risks of future TSF failures will be minimised. But what of acid and metalliferous drainage (AMD)? Caused by sulphide mineral oxidation and once stated by the UN to be the second biggest environmental challenge after climate change, there is no equivalent global management standard has been developed to curtail AMD formation (Figure 2).   

Without a doubt, the EU are global leaders when it comes to tackling mine waste. Their mining industry’s extractive-waste residues represent 29% of total waste output. Mining of Cu, Pb, Zn and Ni has resulted in the production of 600 Mt/year of sulphidic mining waste with associated historic stockpiles containing approximately 28,000 Mt. Powered by multi-million euro EU Horizon grants, transformation of these wastes into potential resources is actively underway through initiatives including the European Training Network for the remediation and reprocessing of sulfidic mining waste sites (SULTAN) and the near-zero waste recycling of low- grade sulphidic mine waste (NEMO) project. Outcomes have included development of processes to manufacture bricks, roof tiles, ceramics and construction blocks from mine waste, establishment of solvometallurgical processing methods to enhance copper recovery, and delivery of new frameworks for valorisation of sulphidic mine waste. But what of critical mineral recovery from mine waste? Back in July 2022, the UK released its first ever critical mineral strategy aiming to improve supply. The priority list of 18 critical minerals, selected by the British Geological Survey, featured cobalt, lithium, indium and vanadium. One wonders perhaps there might have been greater focus on these metals if the SULTAN and NEMO projects had started in 2023?  

In Australia, critical metal exploration has been the much-needed game changer for mine waste. Motivated by the desire to grow the circular economy, which could create an economic benefit of US$ 23 billion in GDP by 2025, mine wastes have been recognised as vital resources to help supply the energy transition. Aligning with the Federal Governments Australian critical metals strategy, State Government agencies have taken the lead in this transformation. Kick-started by Queensland and soon followed by Geoscience Australia and New South Wales, the Northern Territory, and South Australia. Collectively, over US$ 4 M has been invested to explore these once below-grade materials. Teams at The University of Queensland have developed new characterisation workflows and optimised analytical instruments to identify critical mineral commodities in these complex materials. To date, 55 sites have been characterised in detail, with a focus on cobalt, indium and rare earth elements (Figure 3). 

Already in Queensland, research results indicate that cobalt is hosted primarily in pyrite (and other sulfides) around the Mt Isa-Osborne mine region. Geologically, cobalt is associated with iron oxide copper gold and sediment hosted deposits. Back-of-the-envelope calculations indicate there could be as much as 158,720 t cobalt present in North-West Queensland’s tailings. Based on today’s market price, this could equate to at least US$ 5 Billion dollars’ worth of cobalt. This has already attracted the attention of overseas investors with the Japanese Oil, Gas and Metals National Corporation (JOGMEC) who in 2021 commissioned a metallurgical study into cobalt recovery from tailings at the Rocklands copper mine, Queensland (Figure 4). 

Similarly, in 2021, Rio Tinto announcing their support for the new venture “Regeneration”, a Washington-based start-up aiming to extract valuable minerals and metals from mine tailings, waste rock and water. The mining industry notoriously has a culture of ‘fast-follower’, which ultimately in the short-term could be a big win for both mine operators looking to reduce long-term closure liability costs as well as for the environment.

However, to truly recover this value, more out of the box thinking will be required. For example, it no longer seems fanciful to dream of insitu recovery of critical metals, with active research underway to make this a reality. Additionally, new mineral processing companies are coming online to help crack the potential metallurgical hurdles including Cobalt Blue (extraction of cobalt from pyrite), EnviroGold (treatment of refractory ores) and Lava Blue (targeting alumina, magnesium, and vanadium).   

Conclusions

1. Looking to the future, continued evaluation of mine waste as sources to supplement the demand for critical minerals necessary to meet our future needs is vital. Many new opportunities likely exist in Peru, including evaluating copper mine waste as future resources of cobalt and nickel or even indium and manganese from metallurgical slags. 

2. Such an approach to rethinking mine waste could also help alleviate some ESG pollution related concerns held by communities proximal to mining operations. The real message that should have been delivered by António Guterres at COP26 was not to imply a future where mining shouldn’t exist. It should have been to deliver policies to mandate smarter mining and with a systems-thinking approach. 

3. If we embrace the vital role mine waste has in helping to resource decarbonisation then perhaps the global community will be on a pathway to pushing back the Doomsday clock by a minute or two.   

References

Herrington, R. 2021. Mining Our Green Future, Nature. https://www.nature.com/articles/s41578-021-00325-9

JOGMEC. 2021. https://www.jogmec.go.jp/english/news/release/content/300374614.pdf