Research On The Evolution Of The Metabolism Of The Residential Building System And Its Resource And Environmental Effects In China

Architecture plays an important role in human society.The metabolic process of the building system involves the transfer and accumulation of materials to human society,closely related to socioeconomic development,and has a significant impact on resource consumption and the environment.The prosperity and development of real estate have propelled China to become the world’s largest construction country.The residential building system accounts for an absolute proportion in China’s building system.With the changes in demand and the approaching lifetime of buildings,a large amount of construction and demolition waste will be generated in the future,and their disposal and recycling issues will receive increasing attention.Therefore,this study is based on the stock-driven Material Flow Analysis model,considering the differences between urban and rural areas and provincial levels,to predict the metabolic process of China’s residential building system before 2050.Firstly,determine the specific methods for measuring the metabolism of the residential building system,and process and predict key parameters.Secondly,analyze and predict the historical evolution and future changes in the metabolism of China’s residential building system from 1980 to 2050,including the spatiotemporal patterns of stock,inflow,and outflow.Then,predict the metabolism of 10 main building materials in China’s residential building system from 2021 to 2050.Finally,different recycling scenarios are set up to explore the resource recycling potential and environmental effects of the residential building system.The main research conclusions obtained from this study are as follows:(1)After experiencing rapid growth,the in-use stocks of China’s residential building system is expected to significantly slow down after 2030,reaching around 75 billion square meters by 2050,with urban areas accounting for approximately 80% of the total stocks.Provinces in the eastern and southern coastal areas,such as Shandong and Guangdong,will have the largest in-use stocks of residential buildings.The inflow of residential buildings will generally show a downward trend in the future,with a slow to rapid and then stable decline process,reaching approximately 1.3 billion square meters per year by 2050.The inflow is also mainly in urban areas,accounting for over 65%.There is a gap in the inflow of construction materials among different provinces,with the total scale accounting for 0.2%-8%.Therefore,it is necessary to develop different supply strategies for building materials for different regions.The outflow of residential building systems will continue to grow,reaching approximately 1.4 billion square meters per year by 2050,with a similar urban-rural distribution.There is also a significant gap in the outflow volume among different provinces,such as Shandong,Jiangsu,and Guangdong,which respectively account for 6%-7% of the national total.As low as Ningxia,Qinghai,and Tibet,it only accounts for 0.3%-0.5% of the national total.Therefore,it is necessary to develop different strategies for the demolition and recycling of building materials for different regions or provinces.(2)Among the building materials,sand,gravel,bricks,and cement will be the largest components of China’s residential building system,accounting for approximately 92% of the total in-use stocks of 10 types of building materials.As the largest proportion of metal building materials,steel has the in-use stock of approximately 3.8 billion tons in 2050,with a growth rate of 65% from2021 to 2050.Therefore,active consideration should be given to how to respond to changes in the future demand for steel in the residential building system.Due to a significant downward trend in the inflow of most building materials and an upward trend in the outflow after 2030,it is expected that the inflow and outflow of each building material will gradually approach.Therefore,theoretically,residential building systems can achieve internal circulation of building materials.The domestic production of steel,copper,aluminum,and cement in 2021 exceeded 20% of their social stock in the residential construction system that year,so recycling construction materials can effectively reduce the pressure on domestic production in China.In addition,extending the lifetime of residential buildings has a relatively positive effect on reducing the generation of demolition waste materials,with a cumulative reduction of about 10% of waste materials over 30 years.(3)Based on the current situation of recycling construction waste materials in various provinces of China,this study sets up three recycling scenarios: high,medium,and low.It is concluded that compared with no recycling at all,the net demand for construction materials in China will significantly decrease under all three recycling scenarios,resulting in a cumulative savings of 41%-65% in construction materials.Therefore,the construction waste materials in China’s residential building system will have enormous potential for recycling and resource reuse.Further exploration of the environmental effects of residential building systems reveals that replacing primary materials with secondary materials such as steel,copper,aluminum,and cement can reduce environmental impacts such as climate change,land acidification,human toxicity,and the generation of photochemical oxidizing substances by 13%-46%.Therefore,reasonable disposal and recycling of construction waste can achieve low-carbon development in the construction industry.Finally,based on the research results and relevant conclusions,relevant policy recommendations are proposed from strengthening building construction management,reasonably formulating regional planning,issuing relevant policies and regulations,formulating regional recycling strategies,developing green and energy-saving technologies,and innovating building construction methods.