Progress, Issues, and Countermeasures in the Use of Bulk Industrial Solid Waste for Mine Pit Backfilling and Ecological Restoration(1)

0 Introduction

The construction of ‘waste-free cities’ is a key area for achieving synergistic benefits in pollution reduction and carbon emission reduction, and an important chapter in the solid advancement of the pollution prevention and control campaign. The ‘Opinions of the Central Committee of the Communist Party of China and the State Council on Deepening the Pollution Prevention and Control Campaign’ (2 November 2021) explicitly requires the steady advancement of ‘waste-free city’ construction. During the 14th Five-Year Plan period, China will promote the construction of ‘waste-free cities’ in approximately 100 prefecture-level and above cities, and encourage provinces with the necessary conditions to comprehensively advance the construction of ‘waste-free cities.’

China's solid waste is characterised by its diverse types, large volume, and low utilisation rate. Issues such as illegal transfer and dumping of solid waste, as well as unlawful storage and disposal, are prominent and severely impact China's high-quality sustainable economic development. On the other hand, China has approximately 99,000 abandoned mines, with open-pit mining being the primary extraction method. As the supply-side structural reform in the energy sector continues to advance, the number of abandoned mines in China is expected to increase annually. The number of abandoned mine pits and shafts in China is growing rapidly. During the 13th Five-Year Plan period, approximately 5,500 coal mines were closed nationwide, necessitating urgent ecological restoration and governance efforts.

The ‘Opinions on Accelerating the Construction of a Waste Recycling System’ (State Council Office Document [2024] No. 7) clearly states that, under the premise of meeting environmental quality standards and requirements, channels for the utilisation and disposal of bulk solid waste through ecological restoration and roadbed materials should be facilitated. The ‘Work Plan for the Construction of “Waste-Free Cities” During the 14th Five-Year Plan Period’ (Huan Guiti [2021] No. 114) clearly states that the construction of green mines and ‘waste-free’ mining areas should be fully promoted, and the large-scale utilisation of bulk industrial solid waste in ecological restoration and other fields should be advanced. The implementation of the ‘General Industrial Solid Waste Storage and Landfill Pollution Control Standard: GB 18599-2020’ has alleviated the pressure on the treatment of large-scale industrial solid waste in some regions and played an important role in promoting the construction of ‘waste-free cities.’ Under the premise of controllable environmental risks, using solid waste for mine pit backfilling and implementing ecological restoration in tandem can effectively enhance the resource utilization level of solid waste, improve the ecological environment, and has important practical significance and far-reaching implications for implementing the coordinated and synergistic reduction of pollution and carbon emissions, alleviating the pressure of solid waste treatment, ensuring the high-quality development of regional industry, promoting the transformation from ‘abandoned mines’ to ‘green mountains and clear waters,’ and supporting the construction of ‘waste-free cities.’

Based on literature reviews and actual surveys and summaries of existing cases where large-scale industrial solid waste has been used for pit backfilling and ecological restoration, this paper analyses the application progress of large-scale industrial solid waste for pit backfilling and ecological restoration since the implementation of the ‘control standards,’ identifies existing issues and bottlenecks, and proposes corresponding improvement measures and policy recommendations.

1 Current Status and Progress

1.1 Overview of Solid Waste Generation and Disposal Bottlenecks in China

China's historical total stockpile of solid waste reaches 600×10⁸ to 700×10⁸ tonnes, with an annual increase of 100×10⁸ tonnes, making China the world's largest generator of solid waste. From 2011 to 2021, the annual generation of major industrial solid waste in China ranged from 34.26×10⁸ to 40.38×10⁸ tonnes, with a comprehensive utilisation rate of only 42.16% to 57.65%.

Tailings are the largest volume of major industrial solid waste. Over the past decade, China's tailings generation and comprehensive utilization situation with tailings generation in 2021 reached 14.19×10⁸ tonnes and a comprehensive utilization rate of only 35.27%. Due to characteristics such as large generation volumes and low overall utilization rates, issues such as illegal transfer and dumping of solid waste and difficulties in selecting disposal facility sites are prominent. For example, tailings and coal gangue generated during mining and beneficiation processes have been stored for extended periods, occupying large amounts of land. The low comprehensive utilization rate of tailings and the continuous increase in storage volumes are significant issues.

Central ecological and environmental protection inspections have repeatedly exposed illegal dumping and unlawful stockpiling of large-scale industrial solid wastes such as tailings and coal gangue in many regions, severely impacting China's sustainable economic and social development. Therefore, China faces high solid waste generation intensity, inadequate utilisation, and a high incidence of illegal transfer and dumping incidents, which not only pollute the environment but also waste resources, falling short of the public's growing need for a beautiful ecological environment.

1.2 Coupling ecological restoration with solid waste treatment through backfilling measures has been incorporated into national standards

End-of-pipe cleanup measures are feasible but do not address the root cause. How to effectively resolve the issue of ‘large-scale industrial solid waste treatment and disposal’ is a critical challenge on the path to building a harmonious coexistence between humans and nature. On 29 December 2018, the General Office of the State Council issued the ‘Pilot Work Plan for the Construction of “Waste-Free Cities”’ (State Council General Office Document [2018] No. 128), which clearly requires promoting high-quality regional industrial development, achieving zero growth in the total volume of bulk industrial solid waste storage and disposal, and ensuring zero incidents of illegal transfer and dumping of solid waste.

To standardise solid waste environmental management, on 8 December 2020, the Ministry of Ecology and Environment and the State Administration for Market Regulation jointly issued the ‘General Industrial Solid Waste Storage and Landfill Pollution Control Standard: GB 18599-2020.’ Compared to the previous version, this standard explicitly permits the use of general industrial solid waste for backfilling underground mine voids, as well as for surface excavation areas in open-pit mining, soil extraction sites, underground mining subsidence areas, and natural depressions, effectively expanding utilization and disposal pathways. This supports the goal of achieving ‘zero waste cities’ by promoting the trend toward zero growth in the total volume of storage and disposal of bulk industrial solid waste. Additionally, the application of qualified bulk industrial solid waste in ecological restoration aligns with the dual carbon strategy policy.

1.3 Progress of domestic bulk industrial solid waste backfilling projects

Since the publication of the ‘General Industrial Solid Waste Storage and Landfill Pollution Control Standard: GB 18599—2020’ nearly three years ago, several provinces have successively established corresponding local standards. On 15 August 2022, the Inner Mongolia Autonomous Region Market Supervision Administration approved and published ‘Technical Specifications for the Use of General Industrial Solid Waste in Mine Pit Backfilling and Ecological Restoration: DB15/T 2763—2022.’ Building on the national control standards, this standard provides detailed implementation requirements for backfilling with general solid waste, making it more operational.

From a national perspective, this standard represents an innovative approach to the institutional framework and management of ‘waste-free city’ construction. It enhances the pollution prevention and resource utilization of general industrial solid waste while addressing the issue of sourcing fill materials for ecological restoration in numerous mining pits. The standard holds significant guiding significance for the rational and controlled removal of general industrial solid waste, prevention of secondary pollution, and ecological restoration and governance of mining pit areas. In December 2022, the Baotou Municipal Ecology and Environment Bureau, in collaboration with the Municipal Natural Resources Bureau, submitted a proposal to the municipal government to issue the ‘Baotou Municipal Regulations on the Use of General Industrial Solid Waste for Mine Pits and Ecological Restoration Management.’ This further clarifies the collaborative governance and regulatory responsibilities of various departments and units, providing a solid institutional foundation for the implementation of related backfilling projects. It will continue to expand the application scope of the collaborative governance model, effectively alleviating the pressure of industrial solid waste disposal and mine ecological restoration and governance.

From 2021 to 2023, Baotou City utilised tailings, fly ash, furnace slag, and other general industrial solid wastes for ecological restoration of abandoned sand pits, with a total utilisation volume exceeding 1,000×10⁴ tonnes, and rehabilitated nine abandoned open-pit mines. The Anhui Provincial Market Supervision Administration issued the ‘Technical Specifications for the Disposal and Ecological Restoration of General Industrial Solid Waste in Abandoned Open-Pit Mines’ on 31 July 2023, which stipulates the selection of sites, surveys, design, backfilling, ecological restoration, safety and environmental monitoring, and completion acceptance for projects involving the use of general industrial solid waste for backfilling abandoned open-pit mines and ecological restoration. This provides detailed implementation guidelines for project implementation. In Yulin City, Shaanxi Province, researchers including Li Qiang improved saline-alkali soil using coal gangue as a conditioner, with a coal gangue content of 75% to 85%. The results showed that after applying the soil conditioner, indicators such as soil fertility and above-ground biomass significantly increased. 

To address the disposal of coal gangue, some regions in Shanxi Province encourage the use of coal gangue for land reclamation. Coal gangue land reclamation involves coal production enterprises or coal processing enterprises systematically discharging coal gangue as fill material into abandoned gullies to implement land reclamation and restoration, aiming to improve planting conditions, increase arable land area, and protect the ecological environment. However, the aforementioned policy only applies to certain regions. In other areas such as Linfen, due to limited land resources, land reclamation balance requirements, and arable land red line restrictions, suitable backfilling sites are scarce, making approval difficult, resulting in large volumes of industrial solid waste remaining unprocessed for backfilling.