Assessing the city-level material stocks in landfills and the landfill mining potential of China.

Landfill mining has become an emerging issue in urban metabolism research and environmental remediation practices. Comprehensive understanding of the quantity and distribution of material stocks in landfills, as well as identifying hotspots of landfill mining potential, is of crucial importance. However, high-resolution datasets and systematic analytical tools remain insufficient. This study established a time-series landfill material stock inventory at prefecture level in China. An evaluation system for mining potential of landfills at prefecture level was then constructed using an integrated expert scoring and entropy weight method, based on ten indicators across five dimensions, including environmental impact, energy recovery, resource cycling, economic cost, and social aspect. The results show that over the past twenty years, the material stock in landfills was 2321.07 Tg (10 tons) in China, among which, soil-like materials, ash & stone and plastic & rubber were the three largest fractions, accounting for 61.06 wt%, 18.96 wt%, and 12.69 wt% of the total stock. Regional differences in landfill mining potential were found to be significant, with South China presenting the largest mining potential, while Southwest China showed the lowest. Cities with better economic development in China show the possibility to have greater landfill mining potential. This study established a methodology for the assessment of landfill mining potential for China or other countries, and provided scientific evidences for formulating regional-specific policies on landfill mining in China.