Life Cycle Environmental Costs of Buildings

: Energy consumption and pollutant emissions from buildings have caused serious impacts on the environment. Currently, research on building environmental costs is quite insu ﬃ cient. Based on life cycle inventory of building materials, fossil fuel and electricity power, a calculating model for environmental costs during di ﬀ erent stages is presented. A single-objective optimization model is generated by converting environmental impact into environmental cost, with the same unit with direct cost. Two residential buildings, one located in Beijing and another in Xiamen, China, are taken as the case studies and analyzed to test the proposed model. Moreover, data uncertainty and sensitivity analysis of key parameters, including the discount rate and the unit virtual abatement costs of pollutants, are also conducted. The analysis results show that the environmental cost accounts for about 16% of direct cost. The environmental degradation cost accounts for about 70% of the total environmental cost. According to the probabilistic uncertainty analysis results, the coe ﬃ cient of variation of material production stage is the largest. The sensitivity analysis results indicate that the unit virtual abatement cost of CO 2 has the largest inﬂuence on the ﬁnal environmental cost.


Introduction
With the rapid development of economy, China overtook the US as the world's biggest energy consumer and greenhouse gas (GHG) emitter. About 1.6-2.0 billion m 2 of buildings are constructed every year in China [1], accounting for about 40% of the world's total new buildings [2]. A large amount of GHG will be emitted during the life cycle of buildings, especially in construction and operation stages. In order to achieve the sustainable development of construction, there is a great need to clearly know both the costs and the environment costs of buildings.
At present, there is no common understanding of the concept of environmental cost in the academic circle, and there are still some differences among different research fields. According to United States Environmental Protection Agency (USEPA) [3], how environmental costs are defined depends on how the information is used. Whether a cost can be defined as environmental cost is not absolute but needs to be considered according to specific research purpose. The definition of environmental costs is more representative in the System of Integrated Environmental and Economic Accounting (SEEA) published by the United Nations Statistics Division (UNSD) in 1993 [4]. According to the definition, environmental costs consist of two levels: (1) the use and loss value of natural resources in output and final consumption; (2) the impact value of pollution generated by output and consumption activities on environment. In addition, the United States Council on Environmental Quality divides environmental Energies 2020, 13,1353 3 of 15 The aim of this paper is to establish a single-objective optimization model by converting environmental impact into environmental cost, with the same unit of direct cost. The following investigations are conducted: (1) Firstly, this study builds an LCA model with all processes; (2) A virtual abatement cost of pollutants and environmental degradation cost according to macroscopic data of environmental economic accounting in China is calculated; (3) The green construction measures fee is incorporated into the environmental cost for the characteristics of building construction; (4) In order to analyze the differences in northern and southern parts of China, two residential buildings, one located in Beijing and the other in Xiamen, China, are taken as case studies; (5) Uncertainty analysis is carried out, including model and data uncertainties to evaluate how these sources of uncertainty may affect the environmental cost results; (6) Finally, sensitivity analysis of the environmental costs is conducted to identify major input variables, including the discount rate and the unit virtual abatement costs of pollutants.

Methods
According to the Guideline for Chinese Environmental and Economic Accounting [5] and the characteristics of construction engineering, the environmental costs of buildings are divided into three parts: (1) green construction measures cost, which refers to the practical costs of protecting the environment during construction stage; (2) virtual abatement costs, which are used to control the emissions of pollutants in the life cycle of buildings, including water pollutants, air pollutants and solid waste pollutants, and where C va1 , C va2 and C va3 are the virtual abatement costs of air pollution, water pollution and solid waste pollution, respectively; (3) environmental degradation cost, which is the environmental loss cost caused by the emission and pollution of buildings, where C ed1 , C ed2 and C ed3 are the environmental degradation costs of air pollution, water pollution and solid waste pollution, respectively.
The flowchart of the model is demonstrated in Figure 1. Based on the collected project inventory, three types of environmental pollution including air, water and solid waste pollution will be quantified. Based on the quantified results and the methods proposed in this paper, the virtual abatement costs and environmental degradation costs of the three types of environmental pollution can be obtained. Finally, the total environmental costs of a building will be obtained by adding green construction measures costs of subengineering fees including construction, decoration and erection works. The aim of this paper is to establish a single-objective optimization model by converting environmental impact into environmental cost, with the same unit of direct cost. The following investigations are conducted: (1) Firstly, this study builds an LCA model with all processes; (2) A virtual abatement cost of pollutants and environmental degradation cost according to macroscopic data of environmental economic accounting in China is calculated; (3) The green construction measures fee is incorporated into the environmental cost for the characteristics of building construction; (4) In order to analyze the differences in northern and southern parts of China, two residential buildings, one located in Beijing and the other in Xiamen, China, are taken as case studies; (5) Uncertainty analysis is carried out, including model and data uncertainties to evaluate how these sources of uncertainty may affect the environmental cost results; (6) Finally, sensitivity analysis of the environmental costs is conducted to identify major input variables, including the discount rate and the unit virtual abatement costs of pollutants.

Methods
According to the Guideline for Chinese Environmental and Economic Accounting [5] and the characteristics of construction engineering, the environmental costs of buildings are divided into three parts: (1) green construction measures cost, which refers to the practical costs of protecting the environment during construction stage; (2) virtual abatement costs, which are used to control the emissions of pollutants in the life cycle of buildings, including water pollutants, air pollutants and solid waste pollutants, and where Cva1, Cva2 and Cva3 are the virtual abatement costs of air pollution, water pollution and solid waste pollution, respectively; (3) environmental degradation cost, which is the environmental loss cost caused by the emission and pollution of buildings, where Ced1, Ced2 and Ced3 are the environmental degradation costs of air pollution, water pollution and solid waste pollution, respectively.
The flowchart of the model is demonstrated in Figure 1. Based on the collected project inventory, three types of environmental pollution including air, water and solid waste pollution will be quantified. Based on the quantified results and the methods proposed in this paper, the virtual abatement costs and environmental degradation costs of the three types of environmental pollution can be obtained. Finally, the total environmental costs of a building will be obtained by adding green construction measures costs of subengineering fees including construction, decoration and erection works.

Green Construction Measures Cost
The Chinese government has proposed to levy green construction measures costs to improve the energy efficiency of construction. Green construction measures cost (Cgc) refers to environmental protection fees, which are used to reduce the negative impact of construction and consumption of

Green Construction Measures Cost
The Chinese government has proposed to levy green construction measures costs to improve the energy efficiency of construction. Green construction measures cost (C gc ) refers to environmental protection fees, which are used to reduce the negative impact of construction and consumption of resources under the condition of ensuring engineering quality and safety. The ratio of green construction measure costs to subengineering fees of an actual engineering project is shown in Table 1.

Virtual Abatement Costs
The virtual abatement cost represents the cost of curbing untreated environmental pollutants. Three pollutants categories are included: water pollutants (including COD and ammonia), air pollutants (including SO 2 , dust, fine particulate matter and NO x ) and solid waste pollutants (including household waste in operation stage and building material waste in demolition stage). The virtual abatement cost is calculated based on the quantity of pollutant emissions, i.e., the results of life cycle inventory, and virtual abatement costs of per unit pollutant, which is in accordance with the Guideline for Chinese Environmental and Economic Accounting.

Life Cycle Inventory
The framework selected in this study is in the light of the standards of ISO [20] and the Society of Environmental Toxicology and Chemistry (SETAC) [21]. The functional unit is considered as floor area (m 2 ). The cut-off principle of this study is in reference to previous research [22]: sorting all the building materials according to their mass, with the cumulative quality accounting for more than 80% of the building materials being taken into consideration.
As the two case studies are located in China, a local LCI database, Chinese Life Cycle Database (CLCD), is preferred. Although the life cycle inventory (LCI) has achieved remarkable process since last decade, the local LCI database is not able to cover all the material. Therefore, the Europe Life Cycle Database (ELCD) [23] is used to complete the case studies (see Table 2). • Material production stage Pollutant emissions produced in this stage can be calculated based on the bill of material quantities and the life cycle inventory. A proper material loss rate has been considered in the bill of quantities, which references the Quota of Beijing Construction Project [24].

• Construction stage
The two main sources of pollutant emissions produced in this stage are construction machines and material transportation. Gasoline, diesel and electricity consumed by construction machines are calculated based on National Unified Construction Machinery Quota [25]. In the light of 2013 Statistical Yearbook of China, the average transportation distance is 181 km [2]. It is assumed that building materials are transported by trucks. The average fuel consumption level is about 101.78 L/(kt·km) [13]. The diesel consumption can be calculated as follows: where Q is the diesel consumption; m i is the mass of i-th material; L i is the transportation distance of i-th material, assumed to be 181 km; q mi is the average fuel consumption for transporting per unit material, assumed to be 101.78 L/(kt·km).
• Operation stage Energy consumption during this stage implicates the energy and resources, including electricity, natural gas and water consumption. Since the two case buildings just completed construction, there are no actual maintenance monitoring data. Consequently, the water consumption, electricity consumption and domestic waste production for each person can only be estimated based on the local statistical yearbook [26,27], assuming that each family consists of three people. The number of apartments in the two case study buildings is 78 for Xiamen and 100 for Beijing.
Additionally, the pollutant emissions also include household waste, which can be estimated based on household waste of similar commercial buildings per unit time. For residential buildings, the energy consumption and household waste amount are influenced by per capita consumption and living habits, which can be estimated in the light of the statistical yearbook. For regions in northern China, the environmental costs caused by the consumption of coal for heating cannot be ignored.

• Demolition stage
The data about energy consumption of China's construction in the demolition stage are very scarce. The percentages of landfill, incineration and recycling in this paper are based on the data provided by Fabre [28], Zeng [29] and Lei et al. [30], who collected the current inventory data of construction waste recycle and landfill, mainly considering the resource consumption during recycle and landfill. The inventory data of construction waste is shown in Table 3.

Virtual Abatement Costs of Pollutants
The virtual abatement costs (C va ) generated by the air and water pollution generated during the building life cycle can be quantified based on the bill of quantities and life cycle inventory. The formula is as follows: where Q 1 is the amount of air pollutants, based on LCI; Q 2 is the amount of water pollutants, based on LCI; c va1 is the unit virtual abatement costs of air pollution (see Table 4); c va2 is the unit virtual abatement costs of water pollution (see Table 5).

Virtual Abatement Costs of Solid Waste
The solid waste produced in the building life cycle is composed of building solid waste and household waste.
• Building solid waste The recycle rate of building material in China is considerable low. Most of building solid waste is simply treated by depositing or burying in the suburb, which will cause severe environmental pollution during transportation and deposition [31]. The abatement costs of building solid waste can be calculated as follows: where C va31 is the virtual abatement costs of building solid waste; Q 31 is the total amount of building solid waste; c va31 is the virtual abatement cost per unit building solid waste. According to the results of pollution loss survey data and System of Integrated Environmental and Economic Accounting (SEEA) of pilot provinces, the general industrial solid waste per unit virtual management cost is 22 CNY/t [5].
• Household waste With the development of China's urbanization, most of household waste is disposed after harmless treatment, instead of directly drained off into the natural environment. The definition of harmless disposal is when advanced technology and scientific technology are used in the treatment of municipal solid waste to reduce the environmental impact of solid waste [32]. There are mainly three kinds of garbage harmless treatments: landfill, compost and incineration.
With the promotion of household waste treatment technology, some cities have achieved 100% harmless treatment. In this study, it is assumed that no harm will be caused by household waste after harmless treatment, and the environmental degradation costs can be ignored. The virtual abatement costs of household waste can be calculated as: Energies 2020, 13, 1353 where C va32 is the virtual abatement costs of household waste; Q 32 is the total amount of household waste; c va32 is the transportation costs of household waste; Q k is the amount of household waste treated by different technologies; c vak is the unit virtual abatement costs of each treatment (shown in Table 6). By summing up C va1 , C va2 and C va3 , the total virtual abatement costs of building can be calculated as follows:

Environmental Degradation Costs
Environmental degradation cost (C ed ) indicates the economic value loss caused by the degradation of environmental functions. The environmental degradation cost is calculated by the pollution loss cost method. The pollution loss cost method requires a specific technical approach to conduct a special survey of pollution losses to determine the monetary value of the impact of pollution emissions on local environmental quality. After quantifying these influences, the environmental degradation costs caused by pollution can be determined.
The Chinese government published the Chinese Environmental and Economic Accounting Report 2004 [6]. As some local governments firmly opposed publishing the report, after 2008, there are no updated data that can be used to estimate environmental degradation costs.
In order to estimate the environmental degradation costs, a formula was established in the light of the ratio of environmental degradation costs to virtual abatement costs, shown as: where C ed is the total environmental degradation costs; C vai is the virtual abatement costs of air pollution if i = 1, or water pollution if i = 2, or solid waste pollution if i = 3; r i is the average ratio of environmental degradation costs to virtual abatement costs, according to the Chinese Environmental and Economic Accounting Report 2004 (see Table 7), r 1 = 2.25, r 2 = 1.32, r 3 = 0.31. Based the discussion above, the total life cycle environmental costs can be calculated as: where C e is the total life cycle environmental costs; C gc is the green construction measures costs; C va is the virtual abatement costs; C ed is the environmental degradation costs.
Since the time value of money concerns the effect of time and interest rate on monetary amounts, this effect must be given primary consideration in environmental cost [33]. Present value, also known as present discounted value, is the value of an expected income stream determined at the valuation date. The present value is always less than or equal to the future value due to the potential of interest-earning, which referred to as the time value of money. The most commonly applied model of present valuation uses compound interest.
The present value of the total environmental costs of a building can be expressed as: where C epv is the present value of the total environmental costs; C ep is the environmental cost of the material production stage; C ec is the environmental cost of the construction stage; C eo is the environmental cost of the operation stage; C edem is the environmental cost of the demolition stage; t 1 is the number of annual interest periods during construction stage, assumed to be 2 years; t 2 is the number of annual interest periods during operation stage, assumed to be 50 years; r is the discount rate, assumed to be 7%; A is the equal annual payment; (P|A, r, t i ) is the equal-payment-series present-worth factor at time t i , calculated as ( P|A, r,

Case Description
To compare the environmental cost of residential buildings during the operational stage, two sites were selected as case study buildings. One is in Beijing, and the other is in Xiamen, which represent two different climate zones in China. According to the construction organization flow chart, the construction period is 2 years. The major construction materials include concrete, rebar, steel tube, cement mortar, wood, aluminum, glass and alkyd paint. The specific information and corresponding direct costs of the two case buildings are shown in Table 8.

Results Analysis
Based on the calculation method mentioned above, per capita energy consumption level of residents in Xiamen and Beijing were calculated based on China's Yearbook. The environmental costs of the two case studies are shown in Figures 2-5.
Most of the input data used in this case study comes from actual utility bills. However, due to the inevitable limitations of the input data, corresponding assumptions were made during the analysis. Considering the variability of critical input variables, sensitivity analysis of key parameters was conducted. Sensitivity analysis is the measurement of changes in one or more uncertainties to determine the extent to which changes in each factor affect the expected objective [34]. In this paper, the single-factor sensitivity analysis method is used to quantitatively describe the importance degree of input variables when only one parameter changes by 1%. The calculation formula is as shown in Equation (9).
where E i is the sensitivity parameter of the variable F i ; ∆C ei is the corresponding rate of change in environmental costs (%); ∆F i is the rate of change of the variable F i , taken as 1%.
To find the critical input variables, the sensitivity analysis results are shown in Figure 2. For both of the case study buildings, the sensitivity coefficient of the unit virtual abatement cost of CO 2 is the largest, equaling 0.67, which means that CO 2 has the largest influence on the final environmental cost. Additionally, the unit virtual abatement cost of N 2 O, CH 4 and NO x are also key parameters that may lead to significant changes in the outcome, with values of 0.12, 0.45 and 0.32 respectively. The environmental cost results are not sensitive to the unit virtual abatement cost of CO, COD, dust, NH 4 + , SO 2 , solid waste and VOC.
Energies 2020, 13, x FOR PEER REVIEW 9 of 16 analysis. Considering the variability of critical input variables, sensitivity analysis of key parameters was conducted. Sensitivity analysis is the measurement of changes in one or more uncertainties to determine the extent to which changes in each factor affect the expected objective [34]. In this paper, the single-factor sensitivity analysis method is used to quantitatively describe the importance degree of input variables when only one parameter changes by 1%. The calculation formula is as shown in Equation (9).
where Ei is the sensitivity parameter of the variable Fi; ∆Cei is the corresponding rate of change in environmental costs (%); ∆Fi is the rate of change of the variable Fi, taken as 1%.
To find the critical input variables, the sensitivity analysis results are shown in Figure 2. For both of the case study buildings, the sensitivity coefficient of the unit virtual abatement cost of CO2 is the largest, equaling 0.67, which means that CO2 has the largest influence on the final environmental cost. Additionally, the unit virtual abatement cost of N2O, CH4 and NOx are also key parameters that may lead to significant changes in the outcome, with values of 0.12, 0.45 and 0.32 respectively. The environmental cost results are not sensitive to the unit virtual abatement cost of CO, COD, dust, NH4 + , SO2, solid waste and VOC. Additionally, the data quality indicators (DQI) method [35] (see Table 9) and Monte Carlo simulation were used in this case study to analyze the LCA data quality and uncertainty of the results. The engineering quantity data are all from the engineering quantity list, and the emission factor data are from a database. According to the standard deviation provided in Eco-invent [36], the distribution type of the LCI data is selected as lognormal distribution, and the uncertainty is shown in Table 10. Using the Monte Carlo simulation, the variability of environmental scores associated with the ratio of green construction measures cost to each subengineering fees, transportation distance and the average fuel consumption for each vehicle can be estimated. The selected variables are assumed to be uniform distribution or lognormal distribution (see Table 10), and 10,000 iterations were carried out based on previous studies [37].  Additionally, the data quality indicators (DQI) method [35] (see Table 9) and Monte Carlo simulation were used in this case study to analyze the LCA data quality and uncertainty of the results. The engineering quantity data are all from the engineering quantity list, and the emission factor data are from a database. According to the standard deviation provided in Eco-invent [36], the distribution type of the LCI data is selected as lognormal distribution, and the uncertainty is shown in Table 10. Using the Monte Carlo simulation, the variability of environmental scores associated with the ratio of green construction measures cost to each subengineering fees, transportation distance and the average fuel consumption for each vehicle can be estimated. The selected variables are assumed to be uniform distribution or lognormal distribution (see Table 10), and 10,000 iterations were carried out based on previous studies [37].  Figures 3 and 4 show that the added variability did not significantly change the average values nor did it change the ranking of the four stages in terms of C va , C ed and C gc . The minimum, average and maximum total environmental costs are 412, 616 and 827 CNY/m 2 , respectively, in the Xiamen case study building, while they are 489, 673 and 899 CNY/m 2 , respectively, in the Beijing case study building. The coefficient of variation of the material production stage is the largest, followed by the operation and maintenance stage, while that of the demolition stage is the smallest.
The average value of the case study building in Xiamen is shown in Figure 3, where the total environmental cost is 616.29 CNY/m 2 , of which the biggest contributor to environmental cost is material production stage reaching 330.96 CNY/m 2 , followed by operation stage, 199.40 CNY/m 2 . The environmental cost of demolition stage is negative, which indicates that the recycled material can bring positive environmental benefit. For the case study building in Beijing (shown in Figure 4), the total environmental cost is 672.80 CNY/m 2 . The environmental cost of material production stage is 307.42 CNY/m 2 , followed by operation stage, 247.07 CNY/m 2 , which is slightly higher than that of the Xiamen case building's operation stage. This is possibly because energy consumption of heating is excluded for the case study building in Xiamen, which is located in a hot-summer and warm-winter zone where heating in the winter is not necessary. For the both case study buildings, construction stage is the third largest contributor to the environmental cost of the life cycle. During this stage, the green construction cost accounts for the largest percentage of the total environmental cost, about 65%. Demolition stage has the minimum environmental cost. For the both case study buildings, C ed accounts for about 69% of the total environmental cost during material production stage, operation stage and demolition stage. environmental cost of demolition stage is negative, which indicates that the recycled material can bring positive environmental benefit. For the case study building in Beijing (shown in Figure 4), the total environmental cost is 672.80 CNY/m 2 . The environmental cost of material production stage is 307.42 CNY/m 2 , followed by operation stage, 247.07 CNY/m 2 , which is slightly higher than that of the Xiamen case building's operation stage. This is possibly because energy consumption of heating is excluded for the case study building in Xiamen, which is located in a hot-summer and warm-winter zone where heating in the winter is not necessary. For the both case study buildings, construction stage is the third largest contributor to the environmental cost of the life cycle. During this stage, the green construction cost accounts for the largest percentage of the total environmental cost, about 65%. Demolition stage has the minimum environmental cost. For the both case study buildings, Ced accounts for about 69% of the total environmental cost during material production stage, operation stage and demolition stage.    According to the results of both case studies (see Figure 5), a default discount rate was selected as 7%; the environmental cost in life cycle achieves an indispensable 14% share of the direct cost. However, the existing direct cost of the life cycle often neglects environmental cost, resulting in a great warp between calculation results and actual results. In some research, environmental costs are roughly assumed as 10% of direct costs. Since the percentage adopted is less than the result of this case study, this would lead to an error. In order to consider the variability of discount rate, therefore, this study assumes discount rates of 7%, 12% and 17%. The uncertainty analysis of the two cases shows that the ratio of environmental cost to direct life cycle cost decreases as the discount rate increases, but the change does not exceed 5%. According to the results of both case studies (see Figure 5), a default discount rate was selected as 7%; the environmental cost in life cycle achieves an indispensable 14% share of the direct cost. However, the existing direct cost of the life cycle often neglects environmental cost, resulting in a great warp between calculation results and actual results. In some research, environmental costs are roughly assumed as 10% of direct costs. Since the percentage adopted is less than the result of this case study, this would lead to an error. In order to consider the variability of discount rate, therefore, this study assumes discount rates of 7%, 12% and 17%. The uncertainty analysis of the two cases shows that the ratio of environmental cost to direct life cycle cost decreases as the discount rate increases, but the change does not exceed 5%.
According to the results of both case studies (see Figure 5), a default discount rate was selected as 7%; the environmental cost in life cycle achieves an indispensable 14% share of the direct cost. However, the existing direct cost of the life cycle often neglects environmental cost, resulting in a great warp between calculation results and actual results. In some research, environmental costs are roughly assumed as 10% of direct costs. Since the percentage adopted is less than the result of this case study, this would lead to an error. In order to consider the variability of discount rate, therefore, this study assumes discount rates of 7%, 12% and 17%. The uncertainty analysis of the two cases shows that the ratio of environmental cost to direct life cycle cost decreases as the discount rate increases, but the change does not exceed 5%.

Conclusions
Different from the previous LCCA studies which neglect or roughly estimate environmental cost, this study calculates environmental cost based on life cycle inventory. Besides, this study presents a basic method to improve the calculation of LCCA of a building during its life cycle. Furthermore, a single-objective optimization model is generated by converting environmental impact into environmental cost, which has the same unit as LCC and can help the decision makers to obtain a single optimum design solution. Finally, a quantitative analysis of case study of residential buildings in Xiamen and Beijing has been conducted. Based on the above research, the following conclusions can be drawn: • The environmental costs of residential buildings in Beijing and Xiamen are 679 CNY/m 2 and 640 CNY/m 2 respectively, of which the biggest contributor is material production, followed by operation stage, construction stage and demolition stage.

•
For both of the two case study buildings, the environmental degradation cost accounts for about 70% of the total environmental cost, and environmental cost accounts for about 16% of direct cost.

•
The sensitivity analysis results show that the unit virtual abatement cost of CO 2 has the largest influence on the final environmental cost, followed by N 2 O, CH 4 and NO x . The environmental cost results are not sensitive to the unit virtual abatement cost of CO, COD, dust, NH + 4 , SO 2 , solid waste and VOC.

•
The coefficient of variation of the material production stage is the largest, followed by operation and maintenance stage, while the demolition stage is the most robust.

•
The uncertainty analysis of the two cases shows that the ratio of the environmental cost to the direct life cycle cost decreases as the discount rate increases, but the change does not exceed 5% when the discount rate varies from 7% to 17%.

Limitations
• The total environmental cost of the case study building in Xiamen is 50 CNY/m 2 lower than that of case building in Beijing. However, due to the lack of actual operation data, energy consumption data is analyzed based on the reference of the local yearbook, which represents the general operational energy cost of all buildings, including public buildings and residential buildings. Further research should focus on using specific operation data to increase the reliability and accuracy of the estimation results.

•
The theoretical approach proposed in this study is based on the SEEA, which is an incomplete green GDP accounting method. For example, it does not consider the loss caused by ecological damage, groundwater pollution and soil pollution. Further research will refine the methodology based on a new ISO standard [38] proposed in 2019.

•
Due to the lack of data on construction waste disposal in China, this paper uses the recycle rate of building materials from foreign data. Localization of data for construction waste disposal is still required for in-depth study to obtain accurate values.

Conflicts of Interest:
The authors declare no conflicts of interest.

C e Total life cycle environmental costs C gc
Green construction measures costs C va1 Virtual abatement costs of air pollution C va2 Virtual abatement costs of water pollution C va3 Virtual abatement costs of solid waste pollution C va31 Virtual abatement costs of building solid waste C va32 Virtual abatement costs of household waste C ed1 Environmental degradation cost of air pollution C ed2 Environmental degradation cost of water pollution C ed3 Environmental degradation cost of waste pollution C epv Present value of the total environmental costs C ep Environmental cost of material production stage C ec Environmental cost of construction stage C eo Environmental cost of operation stage C edem Environmental cost of demolition stage Q Diesel consumption Q 1 Amount of air pollutants Q 2 Amount of water pollutants Q 31 Total amount of building solid waste Q 32 Total amount of household waste Q k Amount of household waste treated by different technologies c va1 Unit virtual abatement costs of air pollution c va2 Unit virtual abatement costs of water pollution c va31 Virtual abatement cost of per unit building solid waste c va32 Transportation costs of household waste c vak Unit virtual abatement costs of each treatment m i Mass of i-th material L i Transportation distance of i-th material, assumed to be 181 km q mi Average fuel consumption for transporting per unit material, assumed to be 101.78L/(kt·km) r i Average ratio of environmental degradation costs to virtual abatement costs t 1 Number of annual interest periods during construction stage, assumed to be 2 years t 2 Number of annual interest periods during operation stage, assumed to be 50 years r Discount rate, assumed to be 7% A Equal annual payment ∆C ei Corresponding rate of change in environmental costs (%) ∆F i Rate of change of the variable F i , taken as 1% F i Sensitivity parameter of the variable F i