Estimating life-cycle CO2 emissions of urban road corridor construction: A case study in Xi’an, China

Journal Pre-proof Estimating life-cycle CO2 emissions of urban road corridor construction: A case study in Xi'an, China Li Di, Yuanqing Wang, Liu Yuanyuan, Sun Sijia, Gao Yanan PII:

S0959-6526(20)30080-9

DOI:

https://doi.org/10.1016/j.jclepro.2020.120033

Reference:

JCLP 120033

To appear in:

Journal of Cleaner Production

Received Date: 15 December 2018 Revised Date:

5 January 2020

Accepted Date: 6 January 2020

Please cite this article as: Di L, Wang Y, Yuanyuan L, Sijia S, Yanan G, Estimating life-cycle CO2 emissions of urban road corridor construction: A case study in Xi'an, China, Journal of Cleaner Production (2020), doi: https://doi.org/10.1016/j.jclepro.2020.120033. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Ltd.

The authors confirm contributions to the paper as follows: Study conception and design: Li Di, Wang Yuanqing; Liu Yuanyuan; Data collection: Li Di, Sun Sijia; Analysis and interpretation of results: Li Di, Wang Yuanqing, Liu Yuanyuan; Software: Li Di, Liu Yuanyuan; Draft manuscript preparation: Li Di, Gao Yanan. All authors reviewed the results and approved the final version of the manuscript.

Estimating Life-Cycle CO2 Emissions of Urban Road Corridor Construction: a case study in Xi’an, China

Li Di Department of Transportation Engineering, Chang’an University1 P.O. Box 487, Xi’an, China, 710064 Shaanxi Provincial Transport Planning Design and Research Institute2 Xi’an, China, 710065 Email: [email protected] Wang Yuanqing, Corresponding Author Department of Transportation Engineering, Chang’an University P.O. Box 487, Xi’an, China, 710064 Email: [email protected] Liu Yuanyuan School of Civil and Transportation Engineering, GuangDong University of Technology Mailbox D87, Guangdong, China Email: [email protected] Sun Sijia Department of Transportation Engineering, Chang’an University P.O. Box 487, Xi’an, China, 710064 Email: [email protected] Gao Yanan Department of Transportation Engineering, Chang’an University P.O. Box 487, Xi’an, China, 710064 Email: [email protected]

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ABSTRACT

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The carbon dioxide (CO2) emissions characteristics of urban roads together with the corridors’ municipal construction subprojects, such as drainage, water supply, power pipeline and illumination, are important for estimating the CO2 emissions for urban transportation. This paper aims for analyzing the differences in the CO2 emission characteristics of one typical construction of Chinese urban road corridor in which the structure, materials and technologies are different with other published cases, to identify the important factors of the CO2 emissions and to provide some improving administration suggestions for the research type road. Choosing an example, which is the main urban road (Qinling) reconstruction project in Xi’an city, the documents of construction organization and the design budget estimation of the road are obtained, collected the construction process, machinery type and work time, and transportation distance as three type engineering quantities from five subprojects. Furthermore, the life-cycle assessment (LCA) and uncertainty analysis were applied for Qinling road corridor. The results are: (1) The CO2 emissions of the road subproject accounts for 53.19% of the whole corridor; (2) The CO2 emissions of the lime-fly ash, cement and lime accounts for 26.86%, 19.59%, 15.3% of the whole corridor respectively; (3) The CO2 emissions of on-site transportation, earth work, road building, hoisting accounts for 4.94%, 2.07%, 1.47%, 0.74% of the whole corridor, respectively; (4) The greater CO2 emissions coefficient of elasticity are from the production of lime, cement and asphalt concrete, which is 0.436, 0.134 and 0.125, respectively; (5) Compared with Route 35 reconstruction in New Jersey, the CO2 emissions of Qinling road corridor is 41.5kg/m2 higher because of the the important role of lime-fly ash base layer. To conclusion, important strategies are to decrease the emissions of production of lime and cement, to controll the ineffiecient movement of machinery, and to adopt cleaner materials in the base layer.

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1 INTRODUCTION

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The transportation sector accounts for 27.26% of the energy-related CO2 emissions in the United states has been a key issue affecting global climate change (U.S. Energy Information Administration, 2018). From 1985 to 2016, China's transportation industry was one of the fastest growing industries for energy consumption, with an average annual growth rate of 7.93%, which is higher than the annual growth rate for energy consumption of the entire society (National Bureau of Statistics, 1999-2018). Many studies have focused on the CO2 emissions of vehicle fuels, road vehicles and transportation up till now (Yan and Crookes, 2010; Huo et al, 2007; Zhang et al, 2014; Hao et al, 2012; Duan et al, 2015). However, the CO2 emissions caused by the energy and raw materials consumed in transportation infrastructure construction were not accurately quantified until recently (Stripple, 2001; Huang et al, 2009; Wang et al, 2015). As a main part of the urban transportation infrastructure, urban roads are developing rapidly in China. The annual growth rate of the urban road mileage was approximately 4.3% from 2011 to 2016 (Ministry of Housing and Construction of China, 2017), and urban road construction resulted in significant CO2 emissions. Therefore, research on the CO2 emissions of urban road is necessary. An urban road is quite different from a highway; the former includes not only expressways and arterial, secondary and branch roads but also ancillary facilities such as communication signals, bus stations and greenery (Tang and Shen, 2011; Fancello et al, 2014). In addition, other municipal projects (e.g., pipelines and lighting) are implemented along with urban roads projects.

Keywords: LCA; municipal facilities; uncertainty and sensitivity analysis; emission factor; spreadsheet; lime and cement

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Thus, this paper defines an urban road corridor as a space containing a road, pipelines, public facilities, landscaping and other related infrastructure in an urban area. In addition to the structure, the construction condition of an urban road corridor is also different from that of a highway, as the materials and off-road machinery for urban road construction can be obtained from nearer factories or suppliers than those for a highway, and energy consumption could be based on municipal power, instead of generators during urban road construction. The CO2 emissions of urban roads and other municipal facilities have been estimated for decades (Noland and Hanson, 2015; Guo et al, 2017; Mao et al, 2017; Herz and Lipkow, 2002; Strohbach et al, 2012; Long et al, 2016; Li et al, 2017); however, the results are fragmented, and few studies have considered the overall effect of the main ancillary facilities related to urban road corridors on the life-cycle CO2 emissions. The magnitude of the CO2 emissions of all subprojects in urban road corridor construction is not clear, and comprehensive emission impact factors cannot be found. This paper aims for analyzing the differences in the CO2 emissions characteristics of urban road construction using typical materials and technologies in China, identify the important factors of the CO2 emissions and then provide suggestions to administration. To systematically and comprehensively evaluate the CO2 emissions of an urban road corridor, this paper constructed the models for calculating the life-cycle CO2 emissions along urban road corridors with a Microsoft Excel spreadsheet.

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2.1 Life-cycle assessment

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The construction of urban roads consumes significant amounts of raw materials and uses different types of equipment. Emissions are related to both on-site activities and indirect activities ranging from the initial exploitation of the raw material to the final disposal of the products. LCA is a methodology that is used to estimate and understand the environmental impacts of a product, and ideally, each phase of the life cycle from material extraction to end-of-life disposition is included in the assessment. This method systematically assesses environmental impacts by identifying the flows of energy and materials during a process or activity (International Organization for Standardization, 2008).

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Research on the LCA of road infrastructure dates back to the 1990s, and there have been some developments related to life-cycle emissions analysis methodologies. Stripple (2001) first conducted a partial-scope assessment of life-cycle CO2 emissions from a road project, including activities such as materials production, on-site construction, road maintenance and operation, and the final disposal of the road at the end of its life. Since then, most research has focused on the effects of factors such as the materials and technologies used for construction and the road structure on the life-cycle CO2 emissions of roads (Park et al, 2003; Chan, 2007; Zhang et al, 2009, 2013; Ma et al., 2016). In addition, based on the development of the LCA methodology for road infrastructure, a number of software tools have been designed for assessing the road life cycle. These tools include the PaLATE, ROAD-RES, asPECT and UCPRC models for assessing the environmental impact of the materials production, construction, maintenance and end-of-life stages of the road life cycle (Horvath, 2004; Birgisdottir, 2005; Huang et al, 2009; Harvey et al, 2010).

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2.2 CO2 emissions of urban roads

2 LITERATURE REVIEW

In addition to studies that apply the LCA methodology to highways, an increasing number of

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studies have applied the LCA methodology to assess urban road emissions in recent years. Guo et al. (2017) estimated the greenhouse gas (GHG) emissions of expressways and arterial, secondary, branch and hutong roads (i.e., small streets that can be passed only by a car) based on the stock of the urban road system in Beijing. The GHG emissions of the production stage is 1.85 kt CO2 eq/km, which accounted for the main stage of the life-cycle GHG emissions of the urban road system. Clinker production contributed approximately 73% of the emissions for the production stage. Mao et al. (2017) calculated the carbon emissions of expressways and first- to fourth-class roads in Shenzhen; the emissions of expressways and third-class roads, which were the highest carbon emissions from urban roads, were 2.69 kt CO2 eq /km and 169 kg CO2 eq / m2, respectively. Materials production was a major contributor, accounting for 52.3% of the total carbon emissions from urban roads.

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However, the above studies did not consider the CO2 emissions of the main ancillary facilities such as signal lights and stations and municipal infrastructure such as drainage and water supply. Noland and Hanson. (2015) used the GASCAP model for GHG LCA on an urban road reconstruction project in New Jersey, which included grading, pavement, drainage, and sign structures in four municipalities. The emissions from materials production contributed the majority of the GHG emissions (76.2%). The results of life-cycle emissions from urban roads indicate that road construction (1.85-2.69 kt CO2 eq/km) caused the majority of the emissions and that the materials production stage was the largest contributor of life-cycle emissions for the construction project, accounting for 52%-76.2% of emissions.

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2.3 CO2 emissions of municipal facilities

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Most studies of greening projects have mainly considered the capability for CO2 storage in plants, as the types and designs of plants in greening projects affect CO2 storage (Strohbach et al, 2012; Pataki et al, 2006). Li et al. (2017) estimated the life-cycle CO2 emissions of a greening project along a highway and found that sequestration by plants accounts for approximately 0.17% of transportation’s CO2 emissions. However, considering the CO2 emissions of the construction and maintenance stages, CO2 sequestration by plants would decrease greatly (Strohbach et al, 2012). Few studies have considered drainage and the water supply, and existing studies focus on the effect of pipeline materials on life-cycle GHG emissions; for example, the GHG emissions of nanoclay composite pipe are 54% lower than those for pristine HDPE pipe and 16% lower than those for pristine/recycled HDPE pipe (Long et al, 2016). Due to the larger diameters and greater burial depths of sewers, their CO2 emissions are approximately twice as high as those of water mains (Herz and Lipkow, 2002). The existing LCA researches of roads mainly focused on highways, and there is less studies on urban roads. However, the structure and technical characteristics of urban roads and highways are quite different. At present, there is no reference system framework for LCA research of urban road, and lack of quantitative value of CO2 emissions from urban road construction in the detailed calculation process, which is not conducive to the government, municipal manager, construction units, etc. to clarify the magnitude and source of CO2 emissions of urban road construction, and is not conducive to reducing CO2 emissions of urban road construction. Based on the analysis of the actual construction content, construction technology and engineering characteristics of urban road corridor construction in China, this paper attempts to build a general framework for the calculation of life-cycle CO2 emissions of urban road corridor construction in China, which includes the construction phrase of road, water supply, drainage, power pipeline, greening and illumination project. Furthermore, this paper aims to expand the LCA research cases of urban road, to select the CO2 emissions factors that are in line with the actual productivity level of China, to build the CO2

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emissions calculation model of materials production, on-site construction and material transportation of each subproject, and to check the framework and calculation model taking a case study o f Qinling road construction in Shaanxi Province, China.

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3 STUDY SITE AND MATERIALS

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3.1 The characteristics of urban road corridor project

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An urban road corridor project consists of several main subprojects related to the road, pipelines, illumination, greening, etc. Therefore, the life-cycle environmental impact of an urban road corridor project should aggregate the impacts of all subprojects. Different subprojects use different materials and construction technologies, and defining the scope of these subjects before analyzing the LCA inventory is necessary.

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3.2 The LCA system boundary of urban road corridor construction

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Figure 1 lists the CO2 emissions influence factors of materials production, on-site construction, transportation from each subproject during the urban road corridors construction. As shown in Figure 1, the arrows indicate the relationship between the factors at both ends. The factors include traffic component, geography, natural environment, and infrastructure, there are motor vehicle, no- motor vehicle, pedestrian from traffic component, these factors will influence the value of traffic flow, vehicle proportion and design speed, then these three factors will influence the design parameters of road subproject, like section component, lanes numbers, etc. The factors from geography, natural environment, and infrastructure also influence the parameters of pipelines, power, illumination and greening subprojects. Meanwhile, the design location of road, pipelines, power, illumination and greening subprojects will affect each other. And the design parameters of each subproject will influence the construction quantity and technology, then the content of materials, on-site construction and transportation stage will be change, finally these will influence the CO2 emissions.

(i) There are four types of urban roads: expressways, arterial roads, secondary roads and branch roads (MOHURD, 2012). This paper chose arterial roads as typical roads in terms of vehicle lanes, nonmotor lanes, sidewalks and sidewalks facilities (e.g., bus stations and benches). (ii) A pipeline project includes water supply, drainage, power pipelines, gas pipelines, heat distribution pipelines, and communication cables. The pipelines should lie underground, and laying methods (e.g., direct burial, protective tubes, or pipe trenches) are chosen based on the pipeline types and areas. Power pipelines and communication cables can be lain overhead due to space limitations (MOHURD, 2016). (iii) Illumination, greening and other projects in this paper refer to only facilities within the boundary line of road construction.

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Traffic component Motor vehicle

Geography

Natural enviroment

Slope

Rainfall

Altitude

Water resources

Pedestrian

Non-motor vehicle Traffic flow

Vehicle proportion

Infrastructure Sewage treatment plant Heating station

Pipeline

Section component

Lanes number

Pavement structure

Lane width

Water supply station Location/Supply/Demand

Design speed

Road

Power station

Length

Material

Diameter

Location

Power

Illumination

Greening

Length

Location

Number

Location

Location

Vehicle proportion Pavement thickness

Material

Buried depth

Buried depth

Number

Plant species

Location Quantity

construction technology

Material

Transporation

On-site construction

Species

Vehicle type

Off-road machinery type

Quantity

Distance

Work time

CO2 emissions

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FIGURE 1 The CO2 emissions influence factors of each subproject. The system boundary for analyzing the life-cycle CO2 emissions of Qinling road corridor construction is shown in Figure 2. Limited to the data gathered from this project, this paper considered five subprojects of the Qinling road corridor project: the road, drainage, water supply, power pipeline and illuminating subprojects.

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FIGURE 2 LCA system boundary of the Qinling road corridor project. The data on the types and amounts of materials and work times of off-road machinery were provided by the design budget estimation for the Qinling road, the lists of materials and work times can be seen in Appendix A and B. And the classification and distance for each transportation mode were provided by the construction management department of the Caotang Science and Technology Industrial Base. The component of the road corridor engineering and suppliers of major materials are also showed in Figure 3. Based on the process LCA method, this paper considered only the CO2 emissions associated with the stages of materials production, on-site construction and transportation included in each subproject during the construction phase. The materials production stage begins with raw material extraction, processing and transport to the factory or supplier. The materials include raw materials (e.g., cement, steel, and asphalt), semifinished materials (e.g., concrete) and finished materials (e.g., fire hydrants and streetlights). The on-site construction stage includes all the off-road machinery used in each site of the subproject, and transportation within the construction site is also included. The transportation stage was defined as the assessment of the CO2 emissions of to-site transportation in some recent studies. The CO2 emissions of the transportation stage showed a certain volatility, accounting for 8% to 13.1% of the total CO2 emissions, and it was influenced by the project type (i.e., highway or urban road) and region (Herz and Lipkow, 2002; Horvath, 2004; Ou et al., 2010). Hence, in this paper, the transportation stage includes the transportation of the materials and off-road machinery from the factory or supplier to each subproject construction site, and the transportation vehicles include middle- to heavy-duty trucks. This paper calculates the CO2 emissions of transportation separately to determine the magnitudes of CO2 emissions from

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to-site transportation and find the key factors influencing the CO2 emissions of transportation as a means of providing a guide for construction with low emissions.

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FIGURE 3 Design, approximate location of Qinling road and major materials suppliers.

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3.3 Functional unit

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The functional unit is defined by the goal and scope of each study and other relevant parameters, such as climate, design codes, and local construction practices (Santero et al, 2011). The functional unit is quite different from those in the existing literature due to differences in scenarios. However, some studies used a modified functional unit for comparison. Liu et al. (2017, 2018) defined the functional units as “t/lane-km” and “t/lane-km per time” to estimate the CO2 emissions associated with construction and maintenance activities for highway projects. Mao et al. (2017) used “carbon footprint per m2” to quantify the carbon emissions from different levels of roads.

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There are various structures in urban road corridors, and the attributes of pipelines, streetlights, and greenery are quite different from those of roads. Quantifying the CO2 emissions of the urban road corridor per square meter may improve the accuracy of the comparison between cases. Thus, the functional unit of this study is defined as “kilograms per square meter of urban road corridor”, represented as “kg/m2”.

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3.4 Location and engineering consist of Qinling road corridor 7

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The case study focused on a large reconstruction project, i.e., the construction of Qinling road of the Caotang Science and Technology Industrial Base in the Xi'an High-tech Zone, Shaanxi Province, China. The project runs from Caotang 1st road to the Taipingyu River. The approximate location is showed in Figure 3. The Qinling road is an arterial road with three motor lanes and one nonmotor lane in both directions. This project includes the road, drainage, water supply, power pipelines, and illumination in five municipalities, the cross-sectional structure of Qinling road corridor shown in Figure 3. The project started on July 30, 2009 and was completed on October 30, 2009. This typical sample can provide real and credible results for the CO2 emissions estimation and assessment of a Chinese urban road corridor.

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4 Method

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To calculate the CO2 emissions of an urban road corridor, three main stages of each subproject need to be considered: materials, on-site construction and transportation. Summing the CO2 emissions of the three main stages of all subprojects can yield the total CO2 emissions of the urban road corridor, and the total CO2 emissions are normalized into functional units by using the length and width of the urban road corridor (length × width). This study selected the China-specific emission factors as much as possible. According to the literatures, Zhang et al. (2012) calculated the CO2 emission factors of iron production phase including coking, sintering and ironmaking stage, based on the survey data of large iron-steel companies in China in 2009. Cement concrete and fiberglass produced in China in the CLCD (Chinese Life Cycle Database) database in 2013, which could reflect the local production process and technical characteristics of China, and represent the average production technology level. While, the CO2 emission factors of modified asphalt are less studied in China. Therefore, this study selected the research results of European Asphalt Association with reliable data source in 2009 including the main process of modified asphalt production, and the research time of the emission factor of the asphalt is closed to construction time of the Qinling road construction project.

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4.1 The functions of CO2 emissions estimation

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4.1.1 Materials The total CO2 emissions from materials ( ) are calculated by summing the CO2 emissions from all materials ( ) used in construction activity , as represented by equation (1): =∑

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×

(1)

where is the material type, is the CO2 emission factor of material , kg/t; and is the amount of material , t. Furthermore, the CO2 emission factors of some semifinished and finished materials such as lime-fly ash, asphalt concrete and prime coat oil are calculated by the specific production process by referring to the consumption quota of municipal engineering in Shaanxi Province, which was organized by the Department of Housing and Urban-Rural of Shaanxi Province in 2007. Other semifinished and finished materials are derived from the CO2 emission factors of the raw materials that make up the semifinished and finished materials. 4.1.2 On-site construction The CO2 emissions from on-site construction are obtained by adding the CO2 emissions of all machinery used in the construction activities , as represented by equation (2):

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=∑

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(2)

4.1.3 Transportation The life-cycle CO2 emissions of transportation consider the transportation of materials and machinery from off-site to on-site by the modes mentioned above. The total CO2 emissions from all transportation ( ) for each subproject can be represented by equation (3): = ∑ ((

+

)×∑

×

)

(3)

where is the mode of transportation; is the CO2 emission factor of loaded transportation mode , kg/t·km; is the CO2 emission factor of empty transportation mode , kg/t·km; and is the CO2 emission factor of the fuel multiplied by the fuel consumption of the trucks (loaded or empty) used in the transportation stage and then divided by the loading capacity, kg/t·km. Details can be found in (Duan et al., 2015) and are shown in Table 1. refers to the weight of material , t; refers to the transportation distance of material by transportation mode , km. The distances of loaded and empty transportation are same in this study. The total CO2 emissions of each subproject ( ) are calculated by summing the individual values of each stage, and the total CO2 emissions of the urban road corridor ( ) are obtained by summing the CO2 emissions of each subproject , as represented by equation (4): =∑

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×

where is the machinery type, is the CO2 emission factor of energy used for equipment , kg/(kg/kwh), which are referred from (Ou et al, 2010 and National Development and Reform Commission, 2010), and the units are converted by the authors. All the CO2 emission factors are shown in Table 2; is the consumption of energy per hour for equipment , (kg/kwh)/h; and is the total work time of equipment , h. Furthermore, the rates of off-road machineries in different municipal construction scenarios are calculated depending on quotas of energy consumption of machineries, the quotas are calculated according to the sample survey data of actual municipal construction by experienced experts in Shaanxi Province, which was organized by the Department of Housing and Urban-Rural of Shaanxi Province in 2009.

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×

=∑(

+

+

)

(4)

Finally, the total CO2 emissions per functional unit of urban road corridor ( represented by equation (5):

) can be

=

× where refers to the total CO2 emissions of the urban road corridor, t; and and the length (m) and width (m) of the urban road corridor, respectively.

(5) refers to

TABLE 1 CO2 emission factors of materials, energy and transport Items

Materials

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Steel Iron Cement (P.I.42.5) Lime Modified asphalt Asphalt

Unit kg/t kg/t kg/t kg/t kg/t kg/t

Emissions factors 3545 (Luo et al, 2014) 2100 (Zhang et al, 2012) 920.03 (Wang et al, 2015) 1350 (CLCD, 2013) 295.91 (Blomberg et al, 2011) 248 (Wang et al, 2015)

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Energy*

Transport**

Cement concrete (25 Mpa) Cement concrete (32 Mpa) Sand Stone Gravel Granite Fiberglass Lime-fly ash Asphalt concrete (AC-13) Asphalt concrete (AC-20) Prime coat oil Fire hydrant Diesel Gasoline

kg/m3 kg/m3 kg/m3 kg/m3 kg/m3 kg/m3 kg/t kg/t kg/t kg/t kg/t kg/u kg/kg kg/kg

Electricity

kg/kwh

Heavy-duty truck (Loaded) Heavy-duty truck (Empty) Medium-duty truck (Loaded) Medium-duty truck (Empty)

kg/t·km kg/t·km kg/t·km kg/t·km

250 (CLCD, 2013) 295 (CLCD, 2013) 3.19 (Luo, 2014) 3.11 (Wang et al, 2015) 3.9 (Wang et al, 2015) 61.34 (Zhao et al, 2016) 2080 (CLCD, 2013) 96.05 (calculated by authors) 122.66 (calculated by authors) 116.16 (calculated by authors) 722.83 (calculated by authors) 159.53 (calculated by authors) 4.64 (Ou et al, 2010) 4.24 (Ou et al, 2010) 0.99 (National Development and Reform Commission, 2010） 0.1052 (calculated by authors) 0.0488 (calculated by authors) 0.0926 (calculated by authors) 0.0585 (calculated by authors)

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*The calorific values of diesel, gasoline, and electricity are 42.65 MJ/kg, 43.07 MJ/kg, 3.6 MJ/kg (NDRC, 2008). **The fuel for each type of truck is diesel.

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As shown in figure 4, there are four spreadsheets named Materials, On-site construction, Transportation and Total, respectively. And there are three main stages in the CO2 emissions model using the different parameter from equation (1-3) in each model as input to get the performance of materials, on-site construction and transportation, respectively. Then input the value of CO2 emissions into Total spreadsheet to calculate the CO2 emissions of Qinling road construction by the equation 4 and 5. And all these works fulfilled in Microsoft excel 2016.

4.2 The methods of calculation by using excel

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FIGURE 4 The information about process for the spreadsheet.

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5 RESULTS

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5.1 CO2 emissions from Qinling road corridor construction

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The CO2 emissions of the five subprojects for the Qinling construction project (Fig. 5) illustrate that the road project is the largest contributor (53.19%), while the illumination project is the smallest (0.75%). Of the three main stages of the Qinling road construction project, materials production, especially the power pipeline project, is the largest source of CO2 emissions (92.84%), and on-site construction is the second largest source of CO2 emissions, accounting for between 6.24% and 26.03% for the five subprojects; the CO2 emissions of transportation for the whole project account for slightly more than 1% for all subprojects.

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FIGURE 5 CO2 emissions results of the five subprojects for the three main stages. 5.2 CO2 emissions from materials and on-site construction Figure 6 illustrates that lime-fly ash aggregate is the largest contributor to the total emissions from materials in the road project, accounting for 58.98%. Lime is the major emissions contributor in the drainage projects. For water supply project, iron and lime account for 77.13% of CO2 emissions. For the power pipeline project, steel and cement (including cement concrete) account for 94.96% of CO2 emissions. This paper divides the off-road machinery into nine categories according to their construction characteristics. The CO2 emissions distribution of off-road machinery in the road, drainage and water supply projects illustrate that on-site transportation and earthwork machinery are the main sources of CO2 emissions from off-road machinery in the road, drainage and water supply projects. However, the road-building machinery causes more CO2 emissions than the earthworks in the road project.

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FIGURE 6 Shares of CO2 emissions from materials.

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

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14.34 8.99

30.15

19.62 74.98

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Road 5 6 7 8

29.11

46.42

Earthwork Road building Hoisting Transportation Mixing Processing Pump Welding Power

Drainage Water supply

FIGURE 7 Shares of CO2 emissions from off-road machinery.

6 DISCUSSIONS

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6.1 Uncertainty analysis

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The case selected in this paper named Qinling road, which is located in Xi'an City, Shaanxi Province. With reference to the Consumption Quota of Municipal Gardens and Greening Projects in Shaanxi Province, urban road construction project mainly includes road subproject, water

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supply subproject, drainage subproject, power pipeline subproject, and landscaping subproject. Based on the project design files, this case project includes seven subprojects, namely road, water supply, drainage, power pipeline, illumination subproject, greening subproject and ancillary subproject. The greening subproject is designed and implemented by the urban greening department separately, and the subproject design data was not included in the design files of Qinling road construction project. So, this paper did not calculate the CO2 emissions of the greening project and finally estimated the CO2 emissions from the construction phase of five subprojects including road, water supply, drainage, power pipeline and illumination subproject. According to the CO2 emissions calculation results by Yin et al. (2011) and Huang et al. (2017)in which materials production, on-site construction and transportation stage during greening subproject construction phase is considered, the CO2 emissions of urban road greening subproject calculated is 4.54kg/m2 and 0.63 to 1.78kg/m2, which is 2.86% and 0.4% to 1.12% of the total CO2 emission of Qinling road construction, respectively. The proportion of green subproject to the total CO2 emission is small. As for ancillary subproject, there is uncertainty of whether a urban road project include ancillary subproject and of the ancillary subproject scale or subproject quantity. In addition, the ancillary subproject scale or subproject quantity is usually even smaller than that of greening project. Therefore, the CO2 emissions calculation results of five subprojects including road, water supply, drainage, power pipeline and illumination subproject for Qinling road construction in this paper is valuable.The CO2 emission factors of materials were referred from other researches, the fuel and electricity consumption rate from machineries were obtained from the price list of construction equipment and machinery for construction projects in Shaanxi Province. For different projects in different regions, it was necessary to analyze the uncertainty of these parameters because there were some numerical fluctuations. From the above, this paper selected the high uncertainty and higher CO2 emissions of materials and machineries from Qinling road construction, which includes the lime-fly ash, lime, cement, asphalt concrete and on-site transportation, earthwork, and hoisting machinery. Meanwhile, according to the actual situation, this paper assumed six scenarios (Table 2) to calculate the elasticity coefficients of six factors for total CO2 emissions respectively. Furthermore, for machineries, the most effective method for reducing the work time of these machineries, and according to the reason of long work time of machineries, this paper assumes three specific scenarios based on the construction technique. As for materials, it’s difficult to calculate the CO2 emissions reduction effect on a specific CO2 emission reduction technology, thus this paper changes the CO2 emission factor of these materials to analyze the effect on the total CO2 emission of Qinling road construction. In order to accurately and intuitively analyze the impact of different scenarios on total CO2 emissions of Qinling road construction, this paper assumes that only one variable exists in each scenario, and based on the possible range of variables and referring to the range of values of such analysis in other literature, we finally selected the range of 10%, 15%, 20%, 25% and 30%. TABLE 2 Scenarios of uncertainty analysis Type Construction organization CO2 emission factors

14

Scenario 1 2 3 4 5

Content Lifting distance of hoisting Distance of bulldozer going and returning Transportation distance of dump truck CO2 emission factor of asphalt concrete CO2 emission factor of cement

Change 10%, 15%, 20%, 25%, 30%

8748 6

1 2 3 4 5 6 7 8 9 10 11 12

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

CO2 emission factor of lime

The results in Figure 8 show the uncertainty results for changing the construction organization and CO2 emission factors of the materials. The results show that the greater CO2 emissions coefficients of elasticity is from the production of lime, cement and asphalt concrete, which is 0.436, 0.134 and 0.125, respectively. Compared with the CO2 emission factors of the materials, changing the construction organization of the off-road machinery has less effect on the CO2 emissions of the Qinling road construction. The result showed that the CO2 emissions coefficient of elasticity to the activity of dump truck, hoisting machinery and bulldozer are only 0.037, 0.008 and 0.007, respectively. From the above, it can be seen that the total CO2 emissions have the greatest uncertainty to the production of lime among the factors, while other factors were less.

FIGURE 8 Uncertainty analysis for the main inputs. 6.2 The characteristics of CO2 emission sources from materials and on-site construction The calculation of CO2 emissions from the three main stages in the Qinling road construction show that decrease the CO2 emissions of materials production and on-site construction would be the most effective way to reduce the CO2 emissions of urban road construction. The figure 9 show that lime-fly ash aggregate is the largest contributor, which accounts for 26.86% of the total CO2 emissions from Qinling road construction, while a large amount of lime-fly ash aggregate was used in the semirigid base layer from road subproject. The cement and lime accounts for 19.59% and 15.3% of the total CO2, which were the main materials used in undercousre from sidewalk, drainage, water supply and power pipeline subproject. The CO2 emissions of on-site transportation, earth work, road building and hoisting accounts for 4.94%, 2.07%, 1.47% and 0.74% of the CO2 emissions, respectively. And the most CO2 emissions source of on-site transportation is the heavy transportation of soil and pipes, due to the heavy transportation of soil and pipes, the hoisting machinery consumed a lot of fuel in lifting and installation of pipelines and sockets. In conclusion, decreasing the CO2 emission factor of lime by adopting advanced production technology can most effectively reduce the CO2 emissions of urban road corridor construction, such as adopting a rotary or vertical furnace technology can decrease the CO2 emission factor of lime by 4.44-19.26% (CLCD, 2013). And replacing the lime-fly ash with cement-stabilized gravel

15

8748 1 2 3 4 5 6 7 8 9 10

can greatly decrease the CO2 emissions, but at an increased cost. Adopting advanced production technologies for cement and asphalt concrete also have positive effect on reducing CO2 emissions. Like updating the production technology and equipment, replacing high-carbon fuels with low-carbon fuels, and adopting carbon capture and storage technologies can effectively decrease the CO2 emission factor of cement (Liu et al., 2014). The use of warm-mix asphalt in place of hot-mix asphalt can also reduce emissions (Noland and Hanson, 2015). Meanwhile, use of trucks powered by new energy sources can reduce CO2 emissions from transportation, for example, electric trucks can reduce carbon emissions by 25-89% compared to conventional diesel trucks (Lee et al, 2013).

11 12 13 14

FIGURE 9 The characteristics of CO2 emission sources from major materials. Road

Drainage

Water supply

9

CO2 Emissions （t） ）

8

7.85

7 6 5 4

3.29

3

2.33

2

1.18

1 0 Transportation Earthwork

15

16

Road building

Hoisting

8748 1 2 3

FIGURE 10 The characteristics of CO2 emission sources from on-site construction.

4

6.3 Comparsion between Qinling Road and Route 35 in New Jersey

5 6 7 8 9 10 11 12 13 14 15 16

The case study for Noland’s research is a project for the reconstruction of Route 35 from Berkeley Township to Toms River Township, Ocean County, New Jersey; the project includes road, drainage, and sign structure projects; for the approximate section of NJ Route 35 to be reconstructed under Contract 13130, refer to (Noland and Hanson, 2015). And the GASCAP model was used to determine the total life-cycle CO2 emissions associated with the materials used, on-site construction and transportation of resources for the Route 35. The upstream life-cycle emissions for all components are derived primarily from the GREET model, the on-site construction emissions are derived from EPA's NONROAD model, emissions for on-road vehicles estimated using EPA's MOVES model. This paper lists some CO2 emissions factors for materials and energy (upstream) in Table 3. TABLE 3 CO2 emission factors of materials and energy for Route 35 Items

Materials

Energy (upstream)

17 18 19

Asphalt Concrete Aluminum Steel/iron Stroke Gasoline (10% Ethanol RFG) Gasoline Low Sulfur Diesel

Unit t/short ton t/short ton t/short ton t/short ton

Emission factors 0.02 (Zapata and Gambatese, 2005) 0.22 (Choate 2003) 5.58 (Argonne National Laboratory, 2009) 4.19 (Argonne National Laboratory, 2009)

g/lb

276.29 (Argonne National Laboratory, 2009)

g/lb g/lb

326.72 (Argonne National Laboratory, 2009) 210.1 (Argonne National Laboratory, 2009)

This paper chooses the Qinling road and Route 35 as comparative cases is mainly based on the following reasons:

20 21 22 23 24 25 26 27 28

(i) Qinling road and Route 35 are both typical urban roads, and contain major subprojects, which can comprehensively reflect the CO2 emission characteristics of urban road corridors; (ii) Both Qinling road and Route 35 are asphalt pavements, the materials used are similar. The influence of different construction technologies on CO2 emissions can be explored through comparison; (iii) The source of engineering data for Qinling road and Route 35 are reliable. Therefore, the calculated CO2 emissions of urban road construction have high credibility and reference value.

29 30 31 32 33 34 35

However, there are some differences in the scope and system boundaries of Qinling and Route 35 projects: (1) projects related to sign structures like traffic signals are excluded in Qinling road construction, (the CO2 emissions from these projects account for approximately 1.44% of the total CO2 emissions of Route 35 construction, and so they are not an important component of total CO2 emissions); (2) some considerations of Qinling road corridor construction, especially for the drainage and water supply projects, e.g., fire hydrants, were excluded in Noland’s research. However, according to the results of this research, these components of drainage and water supply 17

8748 1 2 3 4 5 6 7 8

projects, especially fire hydrants, can cause non-negligible CO2 emissions. Hence, this paper considered the CO2 emissions of these materials to make the results more accurate. It is also worth noting that the road structures of Route 35 are assumed based on engineering statistics from the bid for this project, which may not accurate. The characteristics of the two road corridors are shown in Table 4. TABLE 4 Characteristics of urban road corridor Item Road corridor Length (km) Width (m) Project length Area definition Location Road Type Number of lanes (each direction) Width (m)

Qinling road

Route 35

5.28 60 120 days Urban Xi'an

6.44 37.27 762 days Urban New Jersey

Motor lanes

Nonmotor lanes

Motor lanes

Nonmotor lanes

3

1

2

1

3.5

5.5

3.66

3.05

Cross section

9 10

6.3.1 CO2 emissions from urban road construction

11 12 13 14 15 16 17 18

The CO2 emissions of the three main stages for two urban road corridors (Fig. 11) illustrate that emission of Qinling road corridor is 41.5kg/m2 higher than Route 35, and the difference in materials production is the largest, at approximately 42.01 kg/ m2, and that the on-site construction used for the Qinling road is higher than Route 35 for 12.78 kg/m2, while the transportation is opposite. Thus, decreasing the CO2 emissions of materials production and on-site construction would be the most effective way to reduce the CO2 emissions of urban road construction from China, especially for road project.

18

8748

Material 140.36

98.35

On-site construction

16.4

Transportation

3.62

2.08

Route 35

15.37

Qinling 160

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

120

80

40

0

40

80

120

CO2 Emissions (kg/m2 )

FIGURE 11 CO2 emissions of the three main stages from the two roads. 6.3.2 CO2 Emissions from materials

The CO2 emissions of the main materials production for Qinling and Route 35 are displayed in Figure 12. It can be seen that aggregate is the material with the largest difference in CO2 emissions at 41.46 kg/ m2, the Route 35 adopts a flexible base layer, which just used a little aggregate, and the CO2 emissions of it is just 1.2 kg/ m2. But there is much asphalt mixed used in flexible base layer, which caused much more CO2 emissions (33.31 kg/ m2). Meanwhile, the CO2 emissions of the asphalt concrete in Route 35 (22.95 kg/ m2) are larger than those in Qinling (19.15 kg/ m2) due to the thicker surface layer. In addition, lime is the main source of CO2 emissions (24.3 kg/ m2) from the drainage and water supply projects for the Qinling road, while that of Route 35 is zero. Hence, decreasing the CO2 emissions of the lime from the drainage and water supply subprojects is necessary for the Qinling road.

Reinforced Concrete

5.00

Steel/iron

16.75

Asphalt Concrete (AC)/Asphalt

19.15

56.26 1.20

Cement mortar/Concrete

27.98

Lime

27.17

24.30

0.00

Wire

0.73

Other

0.87 50

19

Qingling

6.51

Aggregate 42.66

18 19

Route 35

3.85

40

30

20

0.01 3.34

10 0 10 20 30 2 CO2 Emissions (kg/m )

40

50

60

8748 1 2

FIGURE 12 CO2 emissions of materials from the two roads.

3

6.3.3 CO2 Emissions from on-site construction

4 5 6 7 8 9 10 11 12 13 14

The CO2 emissions and work time for off-road machinery from the Qinling and Route 35 are displayed in Figure 13. It can be seen that the work times for the earthwork, road-building, hoisting and transportation machinery in Qinling are much higher than those of Route 35. The CO2 emissions show the same trend, which indicates that the work time has an important impact on the CO2 emissions. And on-site transportation accounts for a major proportion (52.52%) of the off-road machinery CO2 emissions in Qinling road, the work time is much greater than that for Route 35. The earthwork is the second largest contributor of CO2 emissions for the Qinling road, and its work time is 11.48 times that of Route 35. Hence, to reduce the work time of transportation and earthwork machineries will have the significant effect on decreasing the CO2 emissions of Qinling road construction. 9

450 400

7

350

6

300

5

250

4

200 3.29

3

Work Time (h/km2)

CO2 Emissions (kg/m2)

8.06

8

150 2.36

2.33

2

100 1.18

1

50

0.67

0.39

0.10

0.22

0.04

0 Earthwork Road building

15 16 17 18

Hoisting

CO2 Emissions of Qinling

Transportation

Mixing

CO2 Emissions of Route 35

0.03 <0.01

Processing

0.10 0.02

<0.01 <0.01

Pump

Welding

0.10

0.31

0

Work time of Qinling

Power

Work time of Route 35

FIGURE 13 CO2 emissions and work time for off-road machinery from the two roads.

19

6.3.4 CO2 Emissions from transportation

20 21 22 23 24 25 26 27 28

During the Qinling road construction, materials and off-road machinery were transported from nearby suppliers (see figure 1), and the workers lived near the construction site. Therefore, this paper ignored the CO2 emissions from the transportation to off-road machinery and workers. The distances of transportation for the materials, on-site machinery and workers (Table 5) from Route 35 construction were 8.68 times those of the Qinling road, which caused CO2 emissions to be much higher. TABLE 5 Distance of transportation from the two roads

20

8748 Item Qinling Medium-duty Truck Heavy-duty Truck

Fuel Type

Distance (km)

Diesel Diesel

24045 315546

Route 35 Single unit short-haul truck Combination short-haul truck Dump truck Passenger car Pickup truck

Diesel Diesel Diesel Gasoline Gasoline

552848 924897 1239040 231582 155

1 2

7 CONCLUSIONS

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

This paper estimated the life-cycle CO2 emissions for a real urban road corridor (Qinling) construction project including the five subprojects. The materials production, on-site construction and transportation stages were estimated and measured as functional units. The results show that the road project accounts for the major sources of the Qinling road corridor construction projects and that the lime-fly ash aggregate plays an important role in the high CO2 emissions of the semirigid pavement in the Qinling road construction. And the results of the uncertainty analysis identified that reducing the estimation error of CO2 emissions in lime production stage is necessary for estimating total CO2 emissions of Qinling road construction. Then, the higher emissions sources for the Qinling road corridor construction were determined by comparing the CO2 emissions with those for the Route 35 construction, and the long work times of the machinery used in the Qinling road construction also leads to higher CO2 emissions, obtaining materials, off-road machinery and workers from nearby locations could also provide great reductions in the CO2 emissions from the transportation phase. These findings could help policymakers setting low-carbon policies for urban road corridors in China. Additional research is needed to accomplish a complete LCA. This paper considers the CO2 emissions of five main subprojects from urban road corridor construction, however, other related municipal constructions such as greening and gas pipeline projects which may have influence on the CO2 emissions of urban road corridor construction needed to be supplemented. And the operation and maintenance phases can be analyzed to more comprehensively evaluate the effectiveness of mitigation options. In addition, increasing the number of environmental impact categories considered can avoid the effects of other environmental impacts by improving the performance of one environmental impact.

26

ACKNOWLEDGEMENTS

27 28 29 30

The authors express their gratitude for the financial support from the National Natural Science Foundation of China (No.51878062) and the Fundamental Research Funds for the Central Universities of the Ministry of Education of China (No.300102218404).

31

REFERENCES

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1. Argonne National Laboratory, 2009. GREET 1.8c Fuel Cycle Model.

21

8748 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

2. Birgisdottir H., 2005. Life cycle assessment model for road construction and use of residues from waste incineration, Ph.D. Dissertation in the Institute of Environment and Resources, Technical University of Denmark. 3. Blomberg, T., Bernard, F., Southern, M., 2011. Life Cycle Inventory: Bitumen. European Bitumen Association, Brussels, Belgium. 4. Chan W C., 2007. Economic and Environmental Evaluations of Life-Cycle Cost Analysis Practice: A Case Study of Michigan DOT Pavement Projects. Master of Science Thesis in Natural Resource and Environment, University of Michigan. 5. Choate, W. T., 2003. Energy and Emission Reduction Opportunities for the Cement Industry. 6. CLCD, 2013. IKE & SCU-ISCP, 2013. Chinese Core Life Cycle Database Version 0.8. Available at EBalance 4.7 Software. 7. Corbière-Nicollier, T., Laban, B. G., Lundquist, L., Leterrier, Y., Månson, J. A. E., & Jolliet, O., 2001.Life cycle assessment of biofibres replacing glass fibres as reinforcement in plastics. Resour. Conserv. Recy. 33(4), 267-287. https://doi.org/10.1016/S0921-3449(01)00089-1. 8. Duan, H., Hu, M., Zhang, Y., Wang, J., Jiang, W., & Huang, Q., et al., 2015. Quantification of carbon emissions of the transport service sector in China by using streamlined life cycle assessment. J. Clean. Prod. 95, 109-116. http://dx.doi.org/10.1016/j.jclepro.2015.02.029. 9. Fancello, G., Uccheddu, B., & Fadda, P., 2014. Data Envelopment Analysis (D.E.A.) for Urban Road System Performance Assessment. Procedia - Social and Behavioral Sciences, 111, 780-789. https://doi.org/10.1016/j.sbspro.2014.01.112. 10. Flower D J M, Sanjayan J G. 2007.Green house gas emissions due to concrete manufacture. Int. J. Life. Cycle. Ass. 12(5),282-288. http://dx.doi.org/10.1065/lca2007.05.327. 11. Guo, Z., Hu, D., Zhang, Z., Zhang, P., & Zhang, X., 2017. Material metabolism and lifecycle GHG emissions of urban road system (URS). J. Clean. Prod. 165, 243-253. http://dx.doi.org/10.1016/j.jclepro.2017.07.138. 12. Hanson C S, Noland R B, Rao Cavale K., 2012. Life-cycle greenhouse gas emissions of materials used in road construction. Transport. Res. Rec. 2287(1):174-181. 13. Hao, H., Wang, H., & Ouyang, M., 2012. Fuel consumption and life cycle GHG emissions by China’s on-road trucks: Future trends through 2050 and evaluation of mitigation measures. Energy Policy, 43(C), 244-251. https://doi.org/10.1016/j.enpol.2011.12.061. 14. Harvey, J., Kendall, A., Lee, I. S., Santero, N., Van Dam, T., & Wang, T., 2010. Pavement Life Cycle Assessment Workshop: Discussion Summary and Guidelines. University of California Pavement Research Center Technical Memorandum. 15. Herz R K, Lipkow A. 2002. Life cycle assessment of water mains and sewers. Water Science & Technology Water Supply Water. Sci. Tech-w. Sup. 2(4), 51-58. https://doi.org/10.2166/ws.2002.0120. 16. Horvath A., 2004. A Life-Cycle Analysis Model and Decision-Support Tool for Selecting Recycled Versus Virgin Materials for Highway Applications. University of California at Berkeley.

22

8748 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

17. Huang L. J., Zhang Y., Deng Y. R., et al., 2017. The Carbon Footprint Accounting and Assessment of Urban Green Space – Taking Guzangzhou as an Example. Forest Resources Manag. 2017(2), 65-73. 10.13466/j.cnki.lyzygl.2017.02.012. 18. Huang, Y., Bird, R., & Heidrich, O., 2009. Development of a life cycle assessment tool for construction and maintenance of asphalt pavements. J. Clean. Prod. 17(2), 283-296. https://doi.org/10.1016/j.jclepro.2008.06.005. 19. Huo, H., WANG, Michael, JOHNSON, Larry, & Dongquan, H. E., 2007. Projection of Chinese motor vehicle growth, oil demand, and CO2 emissions through 2050. Transport. Res. Rec. 2038, 69–77. http://dx.doi.org/10.3141/2038-09. 20. International Organization for Standardization. Environmental Management: Life Cycle Assessment: Principles and Framework (Vol. 14040). ISO. Japan 2008. Kyoto Protocol Target Achievement Plan. http://www.env.go.jp/en/earth/cc/kptap.pdf. (Accessed July 8, 2017). 21. Lee, D. Y., Thomas, V. M., & Brown, M. A., 2013. Electric urban delivery trucks: energy use, greenhouse gas emissions, and cost-effectiveness. Environ. Sci. Technol. 47(14), 8022-8030. https://pubs.acs.org/doi/10.1021/es400179w. 22. Li D., Wang Y. Q., Liu Y. Y., Wang D. W., Feng S., 2017. Estimating Life-Cycle CO2 Emissions from Freeway Greening Engineering. CICTP 2017. pp. 2962-2971. 23. Liu L. T., Zhang Y., Shen L., Gao T. M., Xue J.J., Chen F. N., 2014. A Review of Cement Production Carbon Emission Factors: Progress and Prospects. Resour. Sci. 36(1), 0110-0119. 24. Liu Y. Y., Wang Y. Q., Li D., 2017. Estimation and Uncertainty Analysis on Carbon Dioxide Emissions from Construction Phase of Real Highway Projects in China. J. Clean. Prod. 144, 337-346. https://doi.org/10.1016/j.jclepro.2017.01.015. 25. Liu Y, Wang Y. Q., Li D., 2018. Life-cycle CO2 emissions and influential factors for asphalt highway construction and maintenance activities in China. Int. J. Sustain. Transp. 6, 1-13. https://doi.org/10.1080/15568318.2017.1402108. 26. Long, N., Hsuan, G. Y., & Spatari, S., 2016. Life Cycle Economic and Environmental Implications of Pristine High Density Polyethylene and Alternative Materials in Drainage Pipe Applications. J. Polym. Environ. 25, 925–947. https://link.springer.com/article/10.1007%2Fs10924-016-0843-y. 27. Luo, Z., Yang, L., Liu, J., & School, A., 2014. Carbon Dioxide Emission of Office Buildings as Embodied Stage. Journal of Civil, Architectural and Environmental Engineering, 36(5), 37–43. https://doi.org/10.11835/j.issn.1674-4764.2014.05.006. 28. Ma, F., Sha, A., Lin, R., Huang, Y., & Wang, C., 2016. Greenhouse gas emissions from asphalt pavement construction: a case study in china. Int. J. Env. Res. Pub. He. 13(3), 351. http://dx.doi.org/10.3390/ijerph13030351. 29. Mao, R., Duan, H., Dong, D., Zuo, J., Song, Q., & Liu, G., 2017. Quantification of carbon footprint of urban roads via life cycle assessment: Case study of a megacity- Shenzhen, China. J. Clean. Prod. 166, 40-48. https://doi.org/10.1016/j.jclepro.2017.07.173. 30. Ministry of Housing and Urban-Rural Development (China), 2012. Code for design of urban road engineering (CJJ 37-2012). China Architecture & Building Press, Beijing.

23

8748 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

31. Ministry of Housing and Urban-Rural Development (China), 2016. Code for urban engineering pipelines comprehensive planning (GB 50289-2016). China Architecture & Building Press, Beijing. 32. Ministry of Housing and Urban-Rural Development (China), 2017. Statistical bulletin on urban and rural construction for 2016. Urban and Rural Development. 17, 38-43. 33. National Bureau of Statistics, 1999-2018. National Statistical Yearbook (1999-2018), China Statistics Press, Beijing. 34. National Development and Reform Commission, 2008. General principles for calculation of total production energy consumption (GBT2589-2008), China Architecture & Building Press, Beijing. 35. National Development and Reform Commission, 2010. Baseline Emission Factor Regional Power Grids China. http://qhs.ndrc.gov.cn/ 36. National Development and Reform Commission, 2010. China’s Low-carbon Roadmap for 2050: Scenario Analysis of Energy Demand and Carbon emissions. CSPM, Beijing. 37. Noland, R.B., Hanson, C.S., 2014a. Carbon Footprint Estimator, Phase II Volume I GASCAP Model, Report # FHWA-NJ-2014-005. New Jersey Department of Transportation. 38. Noland, R.B., Hanson, C.S., 2014b. Carbon Footprint Estimator, Phase II Volume II e Technical Appendices, Report # FHWA-NJ-2014-006. New Jersey Department of Transportation. 39. Noland R B, Hanson C S., 2015. Life-cycle greenhouse gas emissions associated with a highway reconstruction: a New Jersey case study. J. Clean. Prod. 2015. 107, 731-740. https://doi.org/10.1016/j.jclepro.2015.05.064. 40. Ou, X. M., Zhang, X. L., & Chang, S. Y., 2010. Scenario analysis on alternative fuel/vehicle for China’s future road transport: Life-cycle energy demand and GHG emissions. Energy Policy. 38(8), 3943–3956. https://doi.org/10.1016/j.enpol.2010.03.018. 41. Park, K., Hwang, Y., Seo, S., & Seo, H., 2003. Quantitative Assessment of Environmental Impacts on Life Cycle of Highways. J. Constr. Eng. M. 129(1), 25-31. http://dx.doi.org/10.1061/(ASCE)0733-9364(2003)129:1(25). 42. Pataki, D. E., Alig, R. J., Fung, A. S., Golubiewski, N. E., Kennedy, C. A., & Mcpherson, E. G., et al., 2006. Urban ecosystems and the North American carbon cycle. Global. Change. Biol. 12(11), 2092-2102. http://dx.doi.org/10.1111/j.1365-2486.2006.01242.x. 43. Santero, N. J., Masanet, E., & Horvath, A., 2011. Life-cycle assessment of pavements. Part I: Critical review. Resour. Conserv. Recy. 55(9), 801-809. http://dx.doi.org/10.1016/j.resconrec.2011.03.010. 44. Stripple, H., 2001. Life cycle assessment of road. A pilot study for inventory analysis. Rapport IVL Swedish Environmental Research Institute. 45. Strohbach, M. W., Arnold, E., & Haase, D., 2012. The carbon footprint of urban green space—A life cycle approach. Landscape. Urban. Plan. 105(4), 220-229. https://doi.org/10.1016/j.landurbplan.2012.02.003.

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46. Tang J, Shen W., 2011. Research on Planning and Design of Road Cross-Section in Urban New District. Transport Standardization. 8, 144-148. https://doi.org/10.3869/j.issn.1002-4786.2011.08.045. 47. U.S. Energy Information Administration, 2018. Annual Energy Outlook 2018. Government Printing Office. 48. Wang, X., Duan, Z., Wu, L., & Yang, D., 2015. Estimation of carbon dioxide emission in highway construction: a case study in southwest region of China. J. Clean. Prod. 103, 705-714. https://doi.org/10.1016/j.jclepro.2014.10.030. 49. Yan X, Crookes R J, 2010. Energy demand and emissions from road transportation vehicles in China. Prog. Energ. Combust. 36(6), 651-676. https://doi.org/10.1016/j.pecs.2010.02.003. 50. Yin L. H., Yao Z. Y., Wan. M., 2012. Research on Carbon Footprint of Landscape Greening Construction – The Landscaping Works for the Open Space of the Optics Valley Road in Wuhan City as An Example. Chinese Landscape Arch. 28(4), 66-70. 10.3969/j.issn.1000-6664.2012.04.018. 51. Zhang, H., Lepech, M. D., Keoleian, G. A., Qian, S., & Li, V. C., 2009. Dynamic Life-Cycle Modeling of Pavement Overlay Systems: Capturing the Impacts of Users, Construction, and Roadway Deterioration. J. Infrastruct. Syst. 16(4), 299-309. http://dx.doi.org/10.1061/(ASCE)IS.1943-555X.0000017. 52. Zhang, H., Keoleian, G. A., & Lepech, M. D., 2013. Network-Level Pavement Asset Management System Integrated with Life-Cycle Analysis and Life-Cycle Optimization. J. Infrastruct. Syst. 19(1), 99-107. http://dx.doi.org/10.1061/(ASCE)IS.1943-555X.0000093. 53. Zhang, S., Wu, Y., Liu, H., Huang, R., Un, P., & Zhou, Y., et al., 2014. Real-world fuel consumption and CO2, (carbon dioxide) emissions by driving conditions for light-duty passenger vehicles in China. Energy. 69(5), 247-257. https://doi.org/10.1016/j.energy.2014.02.103. 54. Zhao B., Zhang J. G., Liu H. Y., Wei W., 2016. Study on Carbon Emissions of The Granite of Garden Pavement. Journal of Nanjing Forestry University (Natural Sciences Edition). 40(4), 101-106. 10.3969/j.issn.1000-2006.2016.04.016. 55. Zhang X., Wu G. M., Wu S. H., et al., 2012. Determination of carbon dioxide emission factors in typical processes for large iron-steel companies. Acta Sci. Circumst. 32(8), 2024-2027. 10.13671/j.hjkxxb.2012.08.009. 56. Zapata P., Gambatese J. A., 2005. Energy consumption of asphalt and reinforced concrete pavement material and construction. ASCE J. Infrastruct. Syst. 1, 9-20. 10.1061/(ASCE)1076-0342(2005)11:1(9).

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Appendix A Quality Materials

Reinforced Concrete Steel Iron Asphalt Concrete Lime-fly ash Aggregate Cement concrete Cement Lime Sand/Gravel/Stock/Granite Brick Wood Prime coat oil

3 4

26

Unit

t t t t t m3 t t m3 kg kg t

Road

Drainage

Water supply

Power pipeline

Illumination

43.52 73.65 / 51038.91 155486.88 2730.94 3018.40 76.02 3778.20 55.97 7.50 142.54

10692.51 12.72 / / 3076.66 / 2658.98 3930.68 6.44 4490.79 708.13 /

26.92 22.90 1163.36 / 1505.48 / 1427.95 1697.13 / 1244.53 153.11 /

5.73 523.65 66.82 / 4136.43 2275.82 1883.42 / 1309.94 14049.21 6.35 /

/ 2.09 / / 469.35 118.72 / / / 517.35 / /

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Appendix B Machinery Diesel air compressor Track-type tractor Sprinkler car Wheeled loader Vibration roller Bareboard roller Automotive asphalt sprayer Asphalt concrete paver Roller concrete mixing motor Powered tipper Crawler crane Truck crane Fork lift hoist Dump truck Truck Steel cut machine Bar bending machine DC electric welding machine Butt welder Pipe bender Blowing machine Electric tamper Woodworking circular saw Woodworking thicknesser Crawler single bucket excavator Motor hoist Vertical drilling machine Pressure testing pump High pressure oil pump Electrode dryer Grader Self-propelled stabilized soil mixer Lathe

3

27

Work time (t) Road 2131.93 20056.22 3043.52 4844.59 2837.33 93446.20 4024.03 8187.43 3954.58 1220.41 412.86 1694.42 / 32325.18 3421.45 0.02 0.02 109.72 0.01 36.86 89.09 81.54 11.94 0.01 / 0.40 0.79 / / / 164.08 112.81 0.20

Drainage / 1195.29 61.31 236.44 / / / / 7059.06 6328.07 6600.77 15904.20 78.28 1577.60 28544.49 6.11 19.04 17.39 2.04 / / 67621.38 3283.98 2.06 3739.25 2406.89 / / 1798.10 / / / /

Water supply / 635.97 / 83.26 / / / / 5848.53 2458.51 10863.83 907.25 23538.29 / 357.36 / / / / / / 36420.08 0.00 0.00 919.99 13.25 50.84 369.47 0.00 16.64 / / /

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☒The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

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