Coal Gangue: Sources, Environmental Risks, and Advances in Resource Utilization

Coal gangue, a major by-product of coal mining, has long posed significant environmental and resource management challenges. With increasing global emphasis on energy transition and environmental sustainability, the comprehensive utilization of coal gangue has emerged as a critical research and policy priority. This review systematically examines the sources, characteristics, environmental impacts, and integrated utilization pathways of coal gangue. First, the formation mechanisms, mineralogical composition, and physicochemical properties of coal gangue are summarized, with particular attention to hazardous constituents and associated environmental risks, including soil and groundwater contamination, atmospheric pollution, and ecological degradation. Subsequently, current technological approaches for coal gangue management and comprehensive utilization are evaluated, including subsidence areas reclamation and underground backfilling, applications in construction materials and energy conversion, extraction of valuable chemical elements and functional materials, ecological soil engineering, and carbon sequestration. The potential contributions of these pathways to waste reduction, resource efficiency, and low-carbon development are critically discussed. Finally, key environmental, technological, and socio-economic considerations influencing sustainable coal gangue utilization are emphasized. This review provides a comprehensive synthesis of existing knowledge and identifies future research directions aimed at advancing environmentally sound, economically viable, and large-scale utilization strategies. The findings are intended to support researchers, policymakers, and industry stakeholders in promoting circular resource systems and sustainable development.