Spatial-temporal dynamics of the built environment toward sustainability: A material stock and flow analysis in Chinese new and old urban areas

The urban built environment has accumulated massive amounts of resources, which is the main hot spot of construction materials and energy consumption in cities. To effectively monitor and manage resources use and waste disposal toward sustainability, this study intended to explore different metabolic paths of the urban built environment, as well as strategies for new and old urban areas separately with the help of material stock and flow analysis. Based on snapshots of 2003, 2010, and 2017 and combined with big data, a four-dimensional geographic information system buildings database of Lixia District in Jinan, China, was compiled for bottom-up stock modeling. Finally, the environmental impact assessment of the buildings' demolition and disposal stage was carried out. The results showed that the building material stock was 142.31 Mt in 2017, with an increase of 69% from 2003. The reinforced concrete buildings increased rapidly from 2003 to 2017, especially in new urban areas, which has boosted demand for steel and cement by more than 150% during these 15 years. The material stock of the old urban area tends to be saturated, whereas the new urban area has experienced a rapid expansion with the material inflow four times as large as the material outflow. Potential recycling of waste concrete can reduce the generation of building demolition waste by 50%, save 0.15 km(2) of land occupation, increase raw material substitution by nearly 10 times, and reduce CO2 emissions by 2.5 times.

Automated summary

The study examines the resource use and waste disposal in the urban built environment towards sustainability. The results show a rapid increase in demand for building materials in new urban areas, especially reinforced concrete buildings. Recycling waste concrete can greatly reduce waste generation and have significant environmental benefits.