Intensity-Based Carbon Reduction Benefits of 'Zero-Waste City' Construction: A Case Study of Mianyang
The 'Zero-Waste City' initiative, centered on source reduction, resource utilization, and safe disposal of solid waste, aims to minimize environmental impact. To quantitatively assess its carbon reduction contribution, this study took Mianyang as a case, systematically collecting data on solid waste generation, utilization, and disposal across industrial, agricultural, and other sectors from 2021 to 2024. Employing an improved WARM model and emission factor method, and incorporating generation, utilization, and disposal intensities, the carbon reduction benefits before (2021–2022) and after (2023–2024) the initiative were evaluated. Results show that despite significant improvements in comprehensive utilization and safe disposal rates, total solid waste generation increased, leading to a net negative carbon effect of -127.6×10^4 tCO2eq based on absolute quantities. However, after stripping economic and population growth factors, intensity-based accounting revealed a cumulative reduction of 10.8×10^4 tCO2eq, demonstrating significant synergistic benefits. The industrial sector contributed the most, with a reduction of 40.2×10^4 tCO2eq, driven by green transformation and enhanced utilization capacity. Conversely, the rising intensity of domestic solid waste generation resulted in a negative benefit of -46.1×10^4 tCO2eq, highlighting a key area for future improvement. The study underscores the necessity of considering both intensity and absolute quantity dimensions in evaluating rapidly developing cities. These findings provide practical evidence and reference pathways for advancing 'Zero-Waste City' construction and synergistic pollution reduction and carbon mitigation under the 'dual carbon' goals.