Tailings valorisation: Opportunities to secure rare earth supply and make mining environmentally more sustainable

The growing global demand for critical metals, such as rare earth elements (REEs), driven by their essential role in advanced technologies, highlights the need for alternative sources beyond traditional mining. This review aims to explore the potential of REE recovery from tailings of various mining activities, as a sustainable solution to meet future demand, reduce dependency on foreign supplies, and mitigate the environmental impacts of tailings storage. The evaluation of existing tailing deposits showed that they are the most potential secondary sources of REE due to their volumes and concentrations with increasing commercial interest. REE beneficiation plants have 36–78 % yields, leaving a significant amount of REE in tailings. Additionally, iron, gold, phosphate, uranium and tungsten mine tailings, red mud, blast furnace slag, coal fly ash and acid mine drainage are discussed as secondary REE containing sources. Since tailings are often low-grade, traditional recovery methods developed for high-grade concentrates may not be suitable, necessitating the development of novel approaches. Implementing additional concentration steps before leaching is often necessary. Biohydrometallurgical methods are typically suitable for low-grade material streams and have shown promise in REE recovery. This review demonstrates that tailings valorisation helps to reduce the environmental footprint of mining operations while providing cost-effective means to extract valuable by-products. Considering these findings, future mining operations should aim to recover less concentrated elements, such as REE, alongside their primary focus metals. This approach would enhance resource efficiency, create future income opportunities, prevent the accumulation of potentially hazardous waste, and thus, support the transition towards a circular economy.