Pathways to sound management of excavated soil and rock: A case study in Shenzhen

Abstract

Due to underground infrastructure and earthworks, the excavated soil and rock (ESR) emerges as the primary construction and demolition (C&D) waste stream in numerous urban areas. The transportation and disposal of ESR entail substantial costs and adverse environmental impacts, necessitating optimized management approaches. However, the environmental and economic evaluation of various ESR disposal methods remains insufficiently explored. This study presents a comprehensive analysis of a city-scale ESR management system through a case study in Shenzhen. This rapidly expanding megacity generated an annual average of 77 million m3 of ESR. We dynamically evaluate the sustainability of ESR management by harnessing a synergistic methodology that integrates material flow cost accounting (MFCA) with life cycle thinking. The findings reveal that cross-regional transportation emerges as the prioritized ESR disposal method, accounting for 72 ± 2% of the total ESR treatment, resulting in greenhouse gas (GHG) emissions of 584 ± 35 kt CO2 eq. and economic costs of 8358 ± 64 million USD per year. Scenario analysis reveals that sound recycling routes, accompanied by policy support, can yield environmental and economic benefits by reducing GHG emissions by 574 ± 55 kt CO2 eq. and generating net profits of 248 ± 15million USD per year in the coming decade. This study exemplifies the complementary methodologies supporting sustainable ESR management in Shenzhen while offering valuable insights for other cities in China and beyond.