Finding new supply options for critical materials – processing of mine tailings

According to WEF, the ongoing transition to a low-carbon economy will substantially increase the demand for critical raw materials^[1]. Given 10–15-year long lead-times for the development of new extraction sites, new innovative supply options could serve as a lever to reduce the potential supply-risk coming from rising demand. Experts claim that reprocessing of tailings could be an opportunity to increase the supply of critical materials^[2].

Introduction to tailings

Tailings are fine-grained waste material that remains at the tail-end of the mining process once desired metals and minerals are isolated from ore deposits^[3]. Worldwide, approximately 16bn tons are estimated to be produced every year, with an already existing global inventory of ~282bn tons of tailings^[4]. Many such tailings, particularly from historical mining sites, contain valuable amounts of critical materials, such as copper, manganese, REE, or titanium^{^[2],[5]}, thus creating potential to serve as a secondary source of these materials. There is growing recognition that mine tailings represent an underutilized secondary resource that could deliver substantial value through reprocessing and comprehensive utilization^[6]. However, extraction from tailings is complicated due to high variance in concentration of critical materials and presence of additives from the extraction process^[7].

Ongoing initiatives supporting recovery from tailings

There are several existing initiatives promoting reprocessing of tailings, leading to reduced waste and a new source of supply for critical raw materials. For example, in Canada, the Ontario Red Tape Reduction package provides greater regulatory flexibility for reprocessing programs^[8]. In the US, the US Geological Survey has created an incentive to explore the potential for critical mineral resources in mine tailings across 14 states^[9]. Similarly, in Chile, the private and public sector are jointly co-financing projects focused on reprocessing waste from iron mines in Atacama and Coquimbo regions^[10]. In Europe, projects such as NEMO are also supporting sustainable mining waste practices and launching pilot programs to recover additional metals from sulfidic ores/ residues^[11].

Emerging pilots for reprocessing of tailings

There are many technologies that focus on tailing reprocessing such as flotation, advanced gravity separation, high-intensity magnet separation, leaching, roasting, or sensor-based sorting^{[12],[13],[14]}. Rio Tinto and Cobalt Blue Holdings are among large mining players which have launched pilots for large scale reprocessing of waste material, utilizing leaching or roasting proprietary technologies^[14],[15].

Rio Tinto, one of the largest metals and mining companies^[16], started production of battery-grade lithium from a waste rock at a mine site in Boron, California, USA. This mine site is expected to have higher concentrations of lithium compared to other lithium extraction projects under development^[17]. In 2021, a pilot project for roasting and leaching of waste rock was launched with a total capacity of 10 t/year of battery grade lithium, serving as a demonstration plant for a full-scale production site with potential capacity of 5,000t of lithium per year, enough to make batteries for ~70,000 electric vehicles^[14].

Another mining giant, Cobalt Blue Holdings (COB), is partnering with Hudbay Minerals to access a tailings storage facility in Canada and extract critical materials utilizing COB’s proprietary minerals processing technology^[15]. This technology can extract critical materials such as gold, silver, copper, zinc, cobalt, and sulfur from tailings utilizing a series of leaching and metal removal steps^[15],[18]. In 2023, companies launched negotiations to commercialize the tailings re-processing facility^[19].

New technologies are also becoming available that are both economically viable and offer enhanced sustainability for reprocessing. For example, Windarra Tailings Project in Western Australia will be using glycine-leaching technology to retreat gold and nickel tailings ^[20].

Feasibility

Based on recent developments, it is estimated that reprocessing of tailings may become an economically viable option for mineral sourcing. Existing research shows, recovery of rare earth elements (REE) from tailings could become economically attractive alternative however, large capital investments and technological advancements are still requiredto improve recovery rates and drive down processing costs^[6].

Experts have described two key enablers: i) incentivizing tailing processing through policies^[8] (some examples described in chapter above), which could lead to further acceleration of pilot projects to commercially de-risk recovery from tailings; and ii) deployment of capital efficiency approaches, for example, modular tailing treatment plants which can be re-constructed at new sites after depletion of tailings storage^[21].

Thus, despite roadblocks, research shows that mine tailing reprocessing is currently an underutilized source of critical minerals that may help to partially reduce the potential supply risk for critical raw materials^[6].

[1] https://www.weforum.org/stories/2024/05/critical-minerals-are-in-demand-how-do-we-make-sure-this-trend-drives-development/

[2] https://www.miningweekly.com/article/-pursuing-critical-minerals-in-discard-tailings-2023-08-14

[3] https://www.undrr.org/understanding-disaster-risk/terminology/hips/tl0044#:~:text=Tailings%20are%20a%20common%20by,water%20(ICMM%2C%202019)

[4] https://www.globalminingreview.com/mining/14112023/clean-teq-accelerates-expansion-into-global-mine-tailings-management/

[5] https://www.trade.gov/market-intelligence/chile-mining-and-rare-earth-elements

[6] https://www.sciencedirect.com/science/article/pii/S221334372401248X

[7] https://www.jouav.com/blog/mine-tailings.html

[8] https://news.ontario.ca/en/release/1005407/ontario-supporting-recovery-of-residual-metals-and-minerals

[9] https://www.usgs.gov/news/national-news-release/usgs-provides-2-million-states-identify-critical-mineral-potential-mine

[10] https://www.trade.gov/market-intelligence/chile-mining-and-rare-earth-elements

[11] https://cordis.europa.eu/article/id/436235-mine-tailings-to-treasure-providing-society-with-sustainable-resources

[12] https://www.miningweekly.com/article/-pursuing-critical-minerals-in-discard-tailings-2023-08-14