How does the "Zero-waste City" strategy contribute to carbon footprint reduction in China?

The "Zero-waste City" program and carbon peak plan are currently vital environmental strategies in China. Solid waste management systems are closely related to greenhouse gas emissions, and "Zero-waste City" programs are highlighted because of their great potential for carbon footprint reduction and pollution mitigation. However, a knowledge gap remains in terms of quantifying the carbon footprint when implementing "Zero-waste City" programs. Here, we developed a methodology for accounting for the carbon footprint of a solid waste management system, and Ningbo city, which is one of the first demonstration "Zero-waste Cities" in China, was chosen as the study case. The material flow and carbon footprint of construction and demolition waste, industrial waste, hazardous waste, sludge, and municipal solid waste were analyzed. The results show that the carbon footprint of the solid waste management system in Ningbo city was -1679.9 Gg CO₂_eq in 2018, which can be divided into 3472.5, 1131.3, and -6283.8 Gg CO₂_eq by Scopes 1, 2, and 3, respectively. According to the scenario analysis, the SWMS in Ningbo city can achieve a carbon footprint reduction potential of at least 5771.5 Gg CO₂_eq by 2025, by implementing the "Zero-waste City" strategy. This suggests that waste minimization, construction and demolition waste recycling, and municipal solid waste recycling are the most effective measures for carbon footprint reduction.