Waste valorization of coal mining waste from a circular economy perspective: A Brazilian case study based on environmental and physicochemical features

Mineral coal reserves are distributed across all continents in more than 70 countries. The extraction and industrial processing of these reserves generate large amounts of tailings. These tailings are composed of three residual fractions: pyritic, clayey, and carbonaceous. In Brazil, approximately 49% of these generated materials is disposed of in controlled industrial landfills. In China, nearly 15% of the total run of mine (ROM) is discarded as waste. In this context, the present study analyzes the valorization potential of such wastes based on the technical-scientific information from recent literature and characterization of the waste generated in southern Santa Catarina, Brazil. This new methodology was performed from a circular economy perspective using the systematic Classification-Potentiality-Quantity and feasibility-Application (CPQvA) criterion for identifying potential applications of these materials. Based on the evaluation criteria, the waste was classified as environmentally nonhazardous and noninert (class II-A). The waste was primarily composed of silica, alumina, and iron oxide (52.43%, 21.35%, and 6.40%, respectively). This chemical characterization and the mineralogical characterization of the predominant phases-quartz, muscovite, and kaolinite-were similar to those of the raw materials used for manufacturing construction materials. The potential analysis of different fractions, based on circular economy principles, inferred that most residual fractions (approximately 60% of the total discarded material) had mineral characteristics and geographical availability. Therefore, coal tailings have great application potential in the construction sector. The separation of the generated waste into different fractions according to their origins and production characteristics will become one of the innovations in the search for cleaner production and a more circular economy.