Current status, challenges, and strategies of coal gangue utilization in the context of green transition

The stock of coal gangue in China has exceeded 7 billion tons with an annual increment of over 800 million tons, making it imperative to address the ecological damage and environmental pollution caused by its above-ground stockpiling. In view of the significant regional differences in coal gangue generation and utilization levels as well as the highly imbalanced development across China, the resource and environmental attributes of coal gangue (including its composition, classification, and physical-chemical properties) along with its potential values and risks are analyzed, and the relevant policy and standard systems are comprehensively sorted out. Specifically, a multi-tiered and all-round policy system featuring “policy guidance-tax incentives-legal supervision” has been basically formed at the national level, while local policies still focus on front-end underground and surface backfilling due to multiple constraints and high technical difficulties in the whole-chain utilization of coal gangue. Additionally, the standards for comprehensive utilization still have significant shortcomings in high-value utilization, green product certification, and pollution control. A detailed analysis is also conducted of the technology development, application status, and existing problems in three aspects: graded quality-based classification and activation pretreatment of coal gangue, large-scale disposal (underground and surface backfilling, power generation, road construction, and low-end building materials production), and high-value utilization (high-end building materials production, chemical raw materials, and soil formation). It points out that three major bottlenecks, namely “lack of standards, regional imbalance, and technical constraints”, still need to be broken through for the comprehensive utilization of coal gangue. Furthermore, it puts forward the three core principles of “reduction, resource utilization, and harmless treatment” and a full-industry-chain technical path. In response to current issues such as raw material fluctuation, standard gaps, and scale bottlenecks, countermeasures are proposed, including establishing a database of “coal gangue material properties”, developing multi-method collaborative composite activation and homogenization adjustment, researching environment-friendly large-scale surface backfilling and efficient underground backfilling technologies, opening up certification channels for coal gangue-based green products, and solving technical bottlenecks in high-value utilization. Finally, it looks forward to the future development directions of coal gangue utilization, such as multi-path high-value utilization, cross-industry and cross-regional collaborative utilization, integration into the carbon trading market, and gangue-free mining technologies.