Resource potential of mine wastes: A conventional and sustainable perspective on a case study tailings mining project

Mine wastes such as tailings contain minerals that can be valorised. However, their resource potential remains widely misjudged because of non-standardised assessment and classification methods. The current United Nations Framework Classification for Resources (UNFC) concept is tested for its applicability to metalliferous tailings mining projects from a private mining company’s perspective with economic focus on a scoping study level. For the case study tailings storage facility (TSF) Cabeco do Piao (Portugal), a rehabilitation scenario, and two resource recovery scenarios with low and high degree of tailings valorisation are defined and evaluated. A risk assessment shows that actions are necessary to protect human health and the environment. Material flows are modelled and a discounted cash flow analysis, under consideration of mineral price uncertainty, indicates the project’s economic viability. The application of the UNFC principles exemplifies that they cover a broad range of aspects in contrast to the conventional classification principles of the Committee for Mineral Reserves International Reporting Standards (CRIRSCO) which focus on techno-economic aspects: TSF rehabilitation is identified as a necessary base case and positive socio-environmental impacts are prioritised. However, the resource recovery scenarios cannot be differentiated with the current UNFC concept. The evaluation reveals the necessity for a stronger user guidance in the assessment and classification process. Additionally, a more detailed subcategorisation is required to identify a project’s benefits and barriers, particularly in social and environmental domains. These aspects are essential for the further development of the UNFC concept to achieve its full potential.