Full length ArticleMaterials demand and environmental impact of buildings construction and demolition in China based on dynamic material flow analysis
Highlights
► The demand for new buildings in urban area will reach at peak in 2030. ► The demand for new non-residential buildings in rural area will keep increasing until 2050. ► Materials demand and related CO2 emissions from new buildings construction will display a strong drop after 2020. ► Prolonging lifetime of buildings has greater effect for timing of the peak in material demand.
Introduction
Human activities make use of an increasing variety of services provided by stocks of capital and consumer goods. Producing, operating, maintaining, and disposing of these stocks causes material and energy flows that interact with the environment (Daniel B. Müller, 2006). Construction and demolition (C&D) waste is one of the largest waste flows in the world. Non-recycled waste results in the loss of construction materials and one of the greatest transformations of the landscape on the earth for final disposal (Douglas and Lawson, 2002, Moffatt and Kohler, 2008). From a broad point of view, recycling and reasonable disposal of C&D waste is not only a simple environmental concern, but also has major influence on the conservation of resources for the whole society, since it avoids excavation of raw materials and provides substitution for materials like steel and cement which requires a significant amount of raw material, energy and funding to produce.
Since the adoption of its well-known reform and open-door policies in 1978, China has been experiencing rapid modernization and urbanization. In a sharp contrast to China's planned economy era, when the government was virtually the sole source of urban housing and when housing shortage prevailed, changing housing conditions in the 1990s illustrate important improvement in the standard of living. Great quantities of buildings are being constructed and the total building floor space in China increased from 10.2 billion m2 in 1980 increased to 52.7 billion m2 in 2008. It is estimated by the Chinese Ministry of Construction that 30 billion m2 of new buildings will be built between 2005 and 2020, accounting for half of the world's new construction during this period (Ma and Bao, 2006).
The construction of such great amount of buildings causes construction materials are increasing strongly. Owing to the demand of the construction sector, China's cement and steel needs have reached a very high level. China has been the largest producer and consumer of cement in the world since 1985 and of steel since 2000 (NBSC, 2005). In 2004, apparent steel consumption in China was 286 Mt/year, about 40% of which is used in building construction. China's cement industry makes a large contribution to environmental impacts. Its output accounts for 50% of the total building material production (BMI, 2004b). Furthermore, the energy consumption of materials industries is about 50%, especially, energy consumption of steel & iron industry and cement accounted for 20% and 10% of the total industrial energy consumption in 2004 (BMRIRE, 2007). If the buildings and infrastructure construction continues, China will inevitably face a shortage of domestic resource supplies (Shen et al., 2005), exert pressure on global markets over the next two decades (Garnaut and Song, 2006) and emissions of greenhouse gasses (GHGs). Furthermore, Some Chinese experts estimated the real life time of the urban buildings constructed in the 1970s and 1980s to be only 30–40 years, and for many rural houses to be not more than 15 years due to their low quality (Hu et al., 2010a). The short lifetime of buildings caused amounts of solid waste. In China, urban C&D waste has reached 30–40% of the total urban waste generation because of the large-scale construction and demolition activities resulting from the accelerated urbanization and city rebuilding (Chui and Yang, 2006). This vast consumption and discarding of materials do not accord with the sustainable development, and aggravate the environment condition and increase the burden of resource. Therefore, the study of future material flows for building is useful for early recognition of environmental problems, resource and waste management.
Yang and Kohler (2008) estimated Chinese building and infrastructure stock and their material input and output through the construction and operation activities from 1978 to 2050. For buildings constructed before 2005, several age cohorts have been constituted. A series of cohorts are also defined for new building stocks constructed every 5 years after 2005. For each cohort and typology of the stock, average age and refurbishment rates are assumed according to the current status and national policies and standards. The building stock of each generation group will all be demolished at the end of its average age. In addition, the specific coefficients concerning building operation energy consumption (embodied energy, and emission coefficients) are from European ECOINVENT database. Therefore, it affected the accuracy to forecast long-term changes in construction and demolition activities and their related environmental impact. Hu et al. (2010a) extended Müller's generic dynamic MFA model (Müller et al., 2004) to simulate the evolution of the floor area stocks in China's urban and rural housing systems from 1900 to 2100. Furthermore, Hu et al. used this model to analyzed material flow for strategic construction and demolition waste management in Beijing (Hu et al., 2010c), and estimated China's iron and steel demand for residential construction and the scrap availability from housing demolition (Hu et al., 2010b). However, about the parameter setting of this model, the lifetime of different structure building is assumed to be same, which directly influenced the accuracy of results.
The present paper aims to estimate the long-term material flow for buildings by using detailed data on the material consumption intensity and provide important information on materials demand, waste generation and CO2 emissions by combining the future policies on building and materials used in building. It is valuable for the evaluation and design of future waste treatment systems with respect to both waste amounts and composition. The efficiency of such systems will further influence the share of material demand covered by primary materials extraction.
Section snippets
MFA model
In this study, we cited and improved a generic dynamic material flow analysis (DMFA) model presented by Hu et al. (2010b) to estimate material demand and environmental impact of buildings construction and demolition in China based on dynamic material flow analysis by considering material recycling, the lifetime of different type building (Fig. 1). Due to the different per capita floor area and buildings structure, the system is divided into two sub-systems, urban and rural building. The demand
Stocks and flows of buildings in China
Urban residential and non-residential buildings stock will reach to 43.9 billion m2 and 35.1 billion m2 respectively in 2050 due to increasing of urbanization and per capita floor area, which is 2.7 and 3.2 times of which in 2010 respectively (Fig. 6). The new construction demand for residential and nonresidential buildings construction in urban area will reach at peak, 1.35 billion m2 and 1.09 billion m2 in 2030, then decline to 1.23 billion m2 and 0.98 billion m2 in 2050 in the low lifetime scenario.
Conclusion
In this study, we estimated materials demand and environmental impact for buildings in China from 1950 to 2050 based on MFA model. We also estimated the effect of prolonging the lifetime of buildings construction and materials recycling on reducing raw material consumption and CO2 emissions.
In the current lifetime and non-recycling scenarios, the demand for residential and nonresidential buildings construction in urban area will reach peak around 2030, since then they will decrease. For rural
Acknowledgements
This research was supported by the Environment Research and Technology development Fund (S-6-4) of the Ministry of the Environment, KAKENHI (21612005, 20330050 and 23510049), Japan, and the Fundamental Research Funds for the Central Universities (lzujbky-2012-144), China.
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