Study On The Calculation And Assessment Approach For The Environmental Impacts Of The Construction Sector

Under the background of fast-paced urbanization and industrialization, the construction sector develops rapidly in China. However, this sector has to face the enormous pressure for reducing resource consumption and environmental emissions. Thus it is meaningful to quantify and assess the environmental impacts of the construction sector in order to control them better.Firstly, the system boundary of environmental impact assessment of the construction sector was defined as the total environmental impacts, which comprise direct and indirect environmental impacts, respectively standing for the environmental impacts from construction itself and those from construction related sectors. In addition, the framework of calculation and assessment is established.Secondly, an input-output life cycle assessment(IO-LCA) model was built and an input-output based hybrid life cycle assessment(IO-HLCA) model was developed in order to calculate the environmental impacts. In the IO-HLCA model, sensitivity analysis was employed to extract the significant energy paths, and the calculation program was written by Matlab software, and thus the computation efficiency can be improved significantly compared with the existing structure path analysis method. The IO-HLCA model was used to calculate the energy consumption and carbon dioxide emission of the construction sector, and the comparison results with process life cycle assessment(P-LCA) and IO-LCA demonstrates that IO-HLCA model ensures complete assessment boundary and improves the accuracy and reliability of results. Moreover, the other environmental impacts were calculated by IO-LCA and P-LCA.Thirdly, a complete structural decomposition model was built and the influencing factors of environmental impact were divided into Leontief effects, intensity effects, treatment effects and final demand effects, respectively representing the impacts of general technical factors, environmental intensity, environmental treatment and the scale of construction on the environmental impacts. And thus the influencing factors were identified and analyzed.Finally, net price method based on market price and virtual governing cost were used to estimate the monetization weights of environmental impacts, and the assessment of environmental impacts was carried out, and pollution deductions index and relative “decoupling” and the “hook” concept analysis model were used to analyze the coordinated development of environment and economics in the construction sector. The results show that: the indirect environmental impacts accounts for the dominant proportion, nevertheless, the proportion of direct environmental impacts is rising; fossil energy occupies the highest proportion, followed by global warming; direct environmental impacts occupy the absolute majority of solid waste and land occupation, and occupy certain proportion of atmospheric suspended particulates, other resources and water; indirect environmental impacts occupy the absolute majority of global warming, acidification, photochemical smog, eutrophication, water body toxicity and fossil energy, and occupy the most of atmospheric suspended particulates, other resources and water; the total environmental impact value is most sensitive to the weight of energy, followed by carbon dioxide and water; the environmental economic efficiency of construction sector is increasing, shaped by weak “decoupling”.