From waste to resources: Recycling MSW incineration ashes in China's construction sector

The rapid urbanization and industrialization in China have significantly increased municipal solid waste (MSW) generation, with incineration emerging as the dominant treatment method. However, this process produces substantial quantities of MSW incineration fly ash (MSWI-FA) and bottom ash (BA), posing environmental risks due to heavy metals, dioxins, and soluble salts. This review consolidates recent advancements in recycling these byproducts into construction materials, addressing technical feasibility, environmental impacts, and policy challenges. A systematic literature analysis (2000-2024) was conducted using Web of Science and China National Knowledge Infrastructure, supplemented by bibliometric analysis via CiteSpace. MSWI-FA is classified as hazardous waste, requiring stabilization via chemical agents (e.g. Na₂HPO₄/Na₂S) or thermal treatments (e.g. vitrification at 1000-1500°C) to immobilize contaminants. In contrast, BA, which is generally classified as non-hazardous, is evaluated as a direct replacement for both fine and coarse natural aggregates in construction, with its geotechnical properties making it suitable for applications in concrete (≤50% substitution), road bases, and as a raw material in ceramics (20-50% substitution). Key applications include cement kiln co-processing, microcrystalline glass production, and geopolymer-stabilized road bases. Despite progress, challenges persist: compositional variability, high pretreatment costs (1,500-3,500 CNY/ton for vitrification), and insufficient long-term leaching data ( > 10 years). Policy gaps, such as outdated leaching standards (GB 5085.3-2007) and limited economic incentives, further hinder scalability. The review underscores the dual benefits of reducing landfill reliance and conserving natural resources, aligning with China's circular economy goals. Future efforts should prioritize hybrid stabilization technologies, lifecycle assessments, and standardized protocols to enhance industrial adoption. By addressing these barriers, MSWI-FA and BA can transition from environmental liabilities to sustainable construction resources, supporting China's waste management and decarbonization targets.Implications: Municipal solid waste incineration (MSWI) fly ash (FA) and bottom ash (BA) are environmental liabilities with resource potential in construction. Hazardous FA requires rigorous stabilization to immobilize heavy metals and dioxins, while non-hazardous BA is a viable substitute for natural aggregates. Widespread adoption is hindered by compositional variability, high pre-treatment costs (1,500-3,500 CNY/ton for FA vitrification), insufficient long-term leaching data, and outdated standards (GB 5085.3-2007). Developing hybrid stabilization technologies and lifecycle-based policies is crucial to transform these ashes into sustainable construction materials, aligning with circular economy and decarbonization goals.