Material metabolism and associated environmental impacts in Pearl River Delta urban agglomeration

Rapid urbanization has resulted in significant bulk materials use, raising concerns over associated environmental impacts and sustainability challenges. However, a significant gap remains in the city-level analysis of bulk materials production, use, and associated environmental impacts in China. This study calculated the stocks and flows of 13 bulk materials and their associated greenhouse gas (GHG) emissions across nine cities in the Pearl River Delta urban agglomeration (PRDUA) of China during 2000-2020. Results showed that total and per-capita material stocks within the PRDUA experienced a continuous increase, with an average annual growth rate of 0.5 Gt/year and 4.4 t/cap/year, respectively. Both material stocks and flows exhibited similar spatial distribution patterns that gradually decreased from the center to the perimeter. As stocks continuously increase, GHG emissions from material production were rising annually, reaching 187.2 Mt CO2e in 2020. While recycling end-of-life materials contributes to reducing GHG emissions, the current limited mass of recycling curtails its broader impacts. This situation highlights a significant untapped potential within the city to meet decarbonization goals. To maximize the carbon reduction benefits, it is essential to enhance recycling efforts. Moreover, it is crucial that recycling strategies are specifically tailored to suit the timing, location, and types of materials involved.