Comprehensive utilization and environmental risks of coal gangue: A review

The amount of coal gangue, a by-product of coal mining and washing, is rapidly increasing with the growing trend of energy consumption. The accumulated coal gangue without appropriate utilization has resulted in a squander of resources, waste disposal and environmental pollution issues. Over the past few decades, there has been wide attention in developing strategies for the utilization of coal gangue due to a cultural shift towards sustainable development coupled with increasing demand for disposing the challenge of coal gangue accumulation. However, to our knowledge, there is no thorough and in-depth review on the series address of coal gangue reuse. In spite of some advantages of using coal gangue, it is notable that negative environmental problems cannot be ignored, so the scientific utilization is necessary to control the environmental impacts. Therefore, the main objective of this paper is to provide a comprehensive literature review of coal gangue utilization in building material production, energy generation, soil improvement and other high-added applications, analyze the worldwide dynamics of the studies on coal gangue utilization and identify the potential environmental risks in various pathways. The key focus of the review is on detecting the potential problems and thus giving recommendations for the solution. In addition, based on the progress of previous research, this paper also points the directions for further research within the field. A bibliometric analysis was developed in China National Knowledge Internet and Web of Science and a systematic review was conducted for related 237 articles to understand the physicochemical properties and utilization characteristics of coal gangue as well as corresponding environmental risks. The results indicated that the number of published articles has increased in recent years, and the researches were mainly from China, with the contribution of 78.94% of the total selected publications. Besides, these researches mainly focused on the utilization of coal gangue, while there was a lack of attention to environmental risks. The findings of the present study open up a new gate for the further application in coal gangue, hopefully motivate future relevant studies and guide the policy-making.