Unlocking resource potential: Mining waste for critical minerals
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2025-03-07
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The increasing demand for minerals in clean technologies is meeting concerns over supply gaps. This prompts a re-evaluation of the financial feasibility of recovering minerals left in mine waste that had a low economic value at the time of extraction, writes THERESA SMITH, ESI Africa News Editor.The technological pathways to recover minerals from mine waste depend on the type andcharacteristics of the mine waste and the specific mineral recovered. The mineral extraction process is similar to the original value chain - crushing, milling classification, separation (including flotation, gravity separation and magnetic separation), leaching or solvent extraction, metal extraction, and metal recovery. However, there are some additional challenges when recovering minerals from mine waste.These include the secondary minerals created during the weathering and disposal process, uneven size and texture of waste particles and mineral oxidation. This last aspect could require adaptations to the primary production process or the development of entirely new technologies. The minerals that can be recovered from mine waste depend on the geology and extraction or processing used when the waste was originally generated. Commonly found minerals within gold and iron tailings could include copper, zinc and some rare earth elements.For copper tailings specifically, metals such as cobalt, zinc and rare earth elements may be found. Rare earth elements are also found in the tailings of tin, phosphate, bauxite, coal, titanium and uranium. Varying levels of the originally targeted commodity may also be found, depending on the ore grade and recovery efficiency of the original process.The International Energy Agency (IEA), in their World Energy Outlook Special Report Recycling of Critical Minerals: Strategies to scale up recycling and urban mining, specifies that mining generates large amounts of waste.The estimate is that around 3 500 large-scale mining operations globally produce more than 100 billion tonnes of solid waste yearly. The report highlights an additional estimated 5.75 billion cubic metres of waste in active, inactive and closed tailings in 2020 for just over 100 of the world's largest miningcompanies, mainly located in the Americas. "As new mines and associated tailings facilities open, the volume of active facilities is expected to grow by 1.7 billion cubic metres by 2025, increasing the amount of tailings worldwide by about 35% since the beginning of this decade. "lf current growth continues, this would mean that the waste quantity generated would reach almost 8.5 billion cubic metres by 2030, 87% higher than the 2020 levels. "This does not include tailings from abandoned sites, where there are an estimated 500 000 abandoned mining sites in the United States alone, as well as those from artisanal mine sites," says the lEA.The paper, Recycling and Reuse of Mine Tailings: A Review of Advancements and Their Implications, published in open access journal Geosciences in 2022, indicates that mining generated 7 billion tonnes of mine tailings annually worldwide, suggesting that 19 billion solid tailings will be accumulated by2025. It enumerates 10 000 abandoned mines in Canada, 50 000 in Australia and 6 000 in South Africa, creating a particularly worrying legacy of environmental damage, along with the 9 500 coal mines in China, which might reach 15 000 by 2050.The IEA's Recycling of Critical Minerals points out companies are actively recovering minerals from mine waste. They specify US Strategic Metals, which has been recovering cobalt from tailings at aformer Superfund site since2019.However, large-scale production from mines is not usual.Companies are, however, starting to actively evaluate the potential of recovering minerals from mine waste. Rio Tinto invested $2 million in regeneration to focus on re-mining and processing waste from legacy mine sites. They aim to extract minerals from water, tailings and waste rock. Barrick Gold is also exploring the possibility of recovery at Nevada Gold mines.They target scandium, nickel, zinc and cobalt using an ion-exchange recovery system to extractmaterial from heap leach copper solutions. In Europe, Euro Manganese is investigating how to recover and refine battery-grade manganese from tailings at a decommissioned pyrite mine site. This is the only known source of manganese suitable for the battery industry in the EU. Otherwise, it is imported from China. The company submitted an application to designate its Chvaletice Manganese Project in the East Bohemian town of Chvaletice as a Strategic Project under the EU's Critical Raw Materials Act(CRMA).This Act (which took effect in May 2024) is designed to ensure the availability of raw materials essential and strategic to Europe's economy and green transition. The CRMA lists more than 30 raw materials and defines high purity (battery grade) manganese as a strategic raw material and manganese as a critical raw material. The benefits of gaining Strategic Project status include potential access tofinancing from numerous private and public sources, such as national banks, EU institutions,regional and national funding authorities, and private financial institutions. “Additionally, Strategic Project status ensures that permitting processes proceed according to the deadlines set in the CRMA, decreasing the scheduling risk related to permitting," Euro Manganese explained when they announced their intention.In their Recycling of Critical Minerals report, the lEA suggest establishing economic incentives for companies to recover minerals from mine waste.Examples include Canada's Critical Mineral Exploration Tax Credit and the Philippines, which imposes fees or taxes per unit of mine waste or tailings produced. Another recommendation is to provide funding through grants or loans for technological R&D to re-mine waste and tailings. The state ofQueensland in Australia provides AUD 5 million to companies seeking to recover value from mining and processing as part of the Queensland Critical Minerals Strategy. Other countries provide funding through industrial policies.The US contributes funding through the Infrastructure Investment and Jobs Act for pilot projects focused on processing, recycling and developing critical minerals, with at least 30% dedicated tosecondary recovery from mine waste and related sources. The lEA also suggests developing or funding mapping and resource estimation systems to provide a comprehensive overview of available mine waste sources. The Geoscience Australia's Atlas of Australian Mine Waste has thus far recorded more than 1000 sites in-country to help identify and use large tailings.The US Geological Survey has invested $2 million from the Bipartisan Infrastructure Law intocooperative agreements with 14 states to study the potential for critical mineral resources in minewaste. Another recommendation is to streamline or clarify the regulatory framework where legislation regarding mine waste resource recovery is patchy or unclear. The Ontario government in Canada has proposed amendments to the Mining Act that would allow applicants to submit a recovery permit application detailing the proposed mine waste recovery activity and remediation plan, thereby eliminating the need for a full, mine site closure plan.The lEA also suggests updating or creating regulations that address the liability barriers associated with mine waste at abandoned or closed sites. Policies such as the proposed US Good Samaritan Act, which allows non-liable parties, such as volunteers and nonprofits to clean up sites without being held responsible for past pollution, could serve as a model.Economic viability: the value or quantity of the mineral may not be enough to justify or incentivise recovery. High investment costs: resource evaluation, capital expenditure and the handling andtransportation of material complicate the business case for recovery. Lack of knowledge and technical expertise: insufficient mapping or understanding of the potential scale of resources, especially atclosed or abandoned sites. Knowledge or technical gaps may exist at companies whose expertise lies in specific segments of the value chain. Difficulty in identifying significant or viable resources deters mine investment and limits the identification of promising opportunities. Current regulatoryframeworks, along with the non-uniformity or ambiguity of relevant legislation for mine waste: forexample, in some jurisdictions, operators who take ownership of mine waste at closed sites to recover minerals or recycle critical minerals inherit associated legal and environmental liabilities, a significant deterrence to starting such a project.
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