GHG Accounting for Pubilc Transport in Xiamen City, China

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Special Focus: Pathways toward low-carbon cities

GHG accounting for pubilc transport in Xiamen city, China

Carbon Management (2011) 2(4), 383–395

Shenghui Cui†1,2, Fanxin Meng1,2, Wei Wang1,2 & Jianyi Lin1,2 How to account for GHG emissions for public transport is now a key issue for low-carbon city development. This study provides a method to evaluate carbon footprinting for public transport systems in Xiamen city, China across the life cycle. This method, which was based on the life cycle assessment approach including three components – infrastructure, fuels and vehicles – was presented to account the GHG emissions of public transport. The GHG emissions of the two kinds of public transport systems (bus rapid transit [BRT] and normal bus transit [NRT]) in Xiamen City were compared. Results showed that the average carbon emissions

of the BRT system was 638.44 gCO2e per person, and that of the NBT system was 2,088.38 gCO2e. If we only took the direct carbon emissions of fuel consumption in the vehicle operation into consideration, the

average carbon emissions were, respectively, approximately 149.08 gCO2e per person and 260.84 gCO2e per person by BRT and NBT system. The results indicated that the effects of energy saving from the BRT system are better than NBT system, which is related to the features of the BRT system such as large volume, energy- saving and environment-friendly vehicle type and exclusive right-of way.

Carbon emission reduction and ‘low carbon economy’ trends under different policy scenarios [4–7]. These stud- development have become the mainstream of the inter- ies only considered the direct emissions (vehicle opera- national community for addressing climate change. tion) and ignored the upstream emissions (road con- Transport has played an especially important role in struction and vehicle manufacture) and the downstream responding to the challenge of averting dangerous cli- emissions (decommissioning and recycling). However, mate change [1]. Transportation is one of the most impor- the upstream and downstream emissions were proven to tant sources of energy consumption and GHG emis- have significant impact on the whole GHG emissions [8]. sions and its proportion in carbon emission is rapidly It is therefore of critical importance to fully account for increasing year by year. In 2050, as much as 30–50% of the GHG emissions of the transportation and to assess the total CO2 emissions are projected to come from the the possible and effective reduction measures. To date, transport sector, compared with today’s 20–25% [2]. A new research interests are to use the life cycle assessment series of studies have accounted for GHG emissions on (LCA) to analyze and evaluate the energy consumption road building, vehicles production, fuel consumption and environmental emissions of transportation. These and other aspects. Huang et al. built a model for pave- studies assessed energy use, GHG emissions and criteria ment construction and maintenance based on life cycle pollutant emissions associated with the full life cycle of assessment method, and calculated the energy consump- various transportation activities. There are two lead- tion and GHG emissions of pavement rehabilitation the ing transportation life cycle models that deserve to be A34 road in the UK [3]. Other studies have estimated the mentioned: the life cycle emissions model (LEM) [9] historical trends of energy demand and the associated and the GHGs, regulated emissions, and energy use in GHG emissions in the road transport sector and future transportation (GREET) model [10].

1Key Lab of Urban Environment & Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China 2Xiamen Key Lab of Urban Metabolism, Xiamen 361021, China †Author for correspondence: Tel.: +86 592 619 0957; E-mail: [email protected]

Key terms ‘Carbon footprint’ has become a Xiamen has experienced a rapid development. From Life cycle assessment (LCA): Analyze widely used term and model in the 1981 to 2009, urban built-up area has been enlarged the environmental influences including public argument about responsibil- into 212 km2 from the inner cities of 12 km2 and the energy use, resource consumption and ity and abatement action against the GDP has increased to 161.9 billion from 700 million. pollutant emissions across the full life threat of global climate change. It With the population growth and urban expansion, cycle of a product for production, use, disposal, recycling and other phases. had a great increase in public appear- the total passenger traffic volume of Xiamen City has ance over the last few months and increased gradually. Buses serve as the main form of Carbon footprint: Amount of carbon emitted over the life stages of a product years, and is now a buzzword widely public transportation in the city, with taxis and ferries including goods and services or a used across the media, the govern- used to a lesser extent. In 2008, there was a total of measure of the exclusive total amount ment and in the business world [11]. approximately 816 million passengers per year from of carbon emission that is directly and indirectly caused by an activity The carbon footprint model has Xiamen City public passenger transport, of which bus including individuals, organizations, been applied in many scales, such played a dominant role; the passenger capacity was sectors and so on, expressed in as product, household, industry, 588 million people per year, accounting for 72.05% CO equivalents. 2 transport, construction, water sup- of the total passengers, and the passenger capacity of Carbon footprint assessment: Method ply and medical treatment [12–21]. taxis was approximately 228.13 million, 27% of the of accounting GHG emission, which has However, GHG accounting stud- total (Table 1). three different approaches: life cycle assessment (LCA), input-output ies focusing on public transport By the end of 2008, a more comprehensive public assessment (IOA) and hybrid life cycle mainly concentrated on certain transportation network was formed. There were 3,011 assessment (hybrid LCA). aspect of transport activities, such buses in use and a total of 218 bus lines including 3 as construction of infrastructure as BRT lines, 18 BRT connecting lines and 197 NBT lines roads, vehicle production, vehicle fuels and a compre- (containing 30 CMB routes and 42 peasants-passen- hensive analysis of the traffic pressure on the environ- gers lines). With a total of 10 taxi companies and 4,209 men. Yet, there is still a lack of GHG accounting on vehicles in Xiamen, the service capacity and quality of the entire transport system, including the full life cycle urban public transportation has improved significantly. carbon footprint of road construction, use, destruc- The BRT system (Project I) in Xiamen City went into tion and recycling disposal as well as vehicle produc- operation at the beginning of September 2008, which tion, operation, scrap and recycling process [22]. Bus is one of principal arterial routes in Xiamen. The BRT rapid transit (BRT) systems have been identified as an system has a total length of 54 km with three trunk inexpensive and efficient public transportation option routes (BRT Line 1, 2 and 3) and 20 tie lines to match. [23–25]. Several studies have evaluated the efficiency and In addition, 120 trunk route buses (with a capacity of environmental effect of the BRT system through cost– approximately 95 passengers each), which travel on benefit analyses or analysis of different scenarios [25–28]. separate bus lanes and 100 feeder line buses (capacity In addition, the previous article has concretely analyzed of 53 passengers) are used in the BRT system, to satisfy and assessed the life cycle emissions of the BRT system a demand of 240,000 passenger trips per day [101]. in Xiamen City [29]. In this study, an evaluation model of GHG account- Methods ing for urban public transport was proposed based on System boundary the theory of carbon footprint assessment. Then, a The system boundary determines the scope for carbon comparative analysis of two kinds of public transport footprint, for example. which life cycle stages should be systems in Xiamen City (BRT and normal bus tran- included in the GHG accounting [30]. Clearly the defini- sit [NBT]) was presented. The results showed that BRT tion of system boundary plays a significant role on the had more advantages in carbon emission reduction in calculating the results of carbon footprint. In this study, comparison with NBT. the carbon footprint transport system can be measured by the carbon footprint of industrial products across the Background of Xiamen public transport system full life cycle, just because the public transport system Xiamen is a coastal city in South eastern China, can be viewed as a special industrial product. Generally which looks out to the Taiwan Strait and borders speaking, public transport systems are composed of three Quanzhou to the north and Zhangzhou to the south. components, namely infrastructure (road and bus sta- It has direct jurisdiction over 6 districts as Siming, tion), fuels and vehicles [31]. The life cycle phases of the Huli, Jimei, Haicang, Tong’an and Xiang’an with an public transport system are illustrated in Figure 1. The area of approximately 1,573 km2. Its registered popu- boundary for public transport infrastructure includes the lation is approximately 1.77 million, and the resident following processes: raw material production, transporta- population is approximately 2.52 million. Being one of tion and construction, operation and maintenance and China’s earliest special economic zones in the 1980s, decommissioning and recycling [32,33]. The boundary for

384 Carbon Management (2011) 2(4) future science group GHG accounting for pubilc transport in Xiamen City, China Research Article

vehicle includes the following phases: Table 1. Passenger capacity of Xiamen city, China public traffic system in 2008. raw material recovery and extraction, transportation and material processing, Key indicators Passenger capacity per year (million) Proportion of the total (%) material production and fabrication, Bus rapid transit 2,375.27 2.91 vehicle component production, vehicle Normal bus transit 41,180.9 50.46 assembly, operation, disposal and recy- Community minibus 15,243.83 18.68 cling [10]. A fuel cycle is a complicated Public traffic aggregate 58,800 72.05 process, including upstream emissions Taxi 22,813 27.95 associated with drilling, exploration and Total 81,613 100.00 production, crude oil transport, refin- Data from [42]. ing, fuel transport, storage and product retail, as well as downstream disposal or recycling of oil Headquarters and Xiamen Municipal Administrative products [9]. Owing to the limited data, this study did Construction Exploitation Parent Company. For the not calculate the carbon footprint of transport phase for infrastructure operation and maintenance, including the finished products of public vehicles and fuels, which the electricity consumption of the bus stops and the road needs to be supplemented and improved in future studies. lamps, the data were from Xiamen Municipal Works and Gardens Administration Bureau. In addition, Data sources the parameters of vehicles in Xiamen BRT and NBT The data regarding the infrastructure construction of system were provided by Xiamen King Long Motor the BRT and NBT system in Xiamen City were directly Group Company. The data regarding the vehicle com- from Xiamen Municipal Administrative Construction ponents were from Xiamen Metal Recycle Company.

Raw material extraction Raw material Upstream emissions of infrastructure extraction of vehicle

Fuel raw Transport Transport material exploitation

Infrastructure material and Vehicle Transport component manufacture components manufacture

Transport Fuel production Transport

Infrastructure construction Transport Vehicle assembly

Infrastructure use Vehicle operation Direct emissions and maintenance and maintenance

Infrastructure demolition Transport Vehicle disposal

Recycling Land filling Recycling

Downstream emissions

Figure 1. The system boundary of the GHG accounting for urban public transport system. Adapted with permission from [29].

future science group www.future-science.com 385 Research Article Cui, Meng, Wang & Lin

Key terms The data regarding the annual # urban transport were predomi- TE = FC ^EO + EP h CO2 equivalent (CO2e): A measure for describing how much global warming a nantly from the Annual Report on Equation 2 given type and amount of GHG may the Development of Transportation, cause, using the functionally equivalent Posts and Telecommunications of where, TE (gCO2e/km·t) is the transport emission; amount or concentration of CO2 as the reference. Xiamen City (in Chinese) during FC (MJ/km) is the fuel consumption, the amount of 2006–2008 and so on. fuel added to the engine, using lower heating value, Global-warming potential (GWP): Relative measure of how much heat a converted from l/km; EO (g/MJ) is the emissions from GHG traps in the atmosphere, Calculating methodology engine operation, g emissions per MJ work energy out- comparing the amount of heat trapped Calculating methodology of put from the shaft of the engine, converted from g/kwh, by a certain mass of the gas in question infrastructure GHG emission to the amount heat trapped by a similar while EP (g/MJ) is the emissions from fuel production The GHG emissions of infra- for transportation of construction materials. mass of CO2, which is expressed as a

factor of CO2 (whose GWP is structure mainly come from the The energy consumption of construction mainly standardized to 1), CH is 21 , and N O is 4 2 five parts: infrastructure mate- includes electricity used for power tools and lighting 310 accroding to IPCC 1996. rial production, construction, as well as diesel fuel used by heavy equipment at the operation&maintenance, decom- construction site. Activities include site preparation, missioning and disposal & recycling. We analyzed the structural and envelope installation, mechanical, elec- infrastructure GHG emissions from the following five trical equipment installation, and interior finishing. phases, respectively. Energy and environmental flows associated with the construction process could not be developed directly, Infrastructure material production since there was no record of equipment use or opera- Infrastructure material production contains four proc- tional hours. Estimates for construction energy con- esses, namely burdens from raw materials extraction sumption in the literature range from 1.2 to 10% of (e.g., drilling for oil and mining for iron ore), trans- embodied energy [37]. The higher values in the Cole portation and processing, refinement of raw materials studies (6.5–10.0% of material embodied energy) into engineered materials, and manufacturing (e.g., included transportation burdens for construction extrusion of steel or aluminum). Carbon emissions workers. Therefore, in this study 5% of total embod-

mainly include three GHG: CO2, methane (CH4) and ied energy is used to account for both structure and

nitrous oxide (N2O) expressed as CO2 equivalent (CO2e); interior according to the literature [38]. Equation 1. Based on the IPCC 1996, the global-warm-

ing potential for the GHGs is that CO2 is 1, CH4 is 21 Operation & maintenance

and N2O is 310 [34–36] . Operation phase activities consist of lighting (road lamps) and equipment operation including escalators,

n card readers and air-conditions. The emissions can Im= / qi ##^ 1 +wih ^ EFECO2,i + FCH4,i ## 21+ EFNO2 ,i 310h i= l be estimated by the electricity consumption of these Equation 1 equipments. Based on the emissions factors (1TJ coal

equivalent releases 92.64 tCO2, 10.00t CH4 and 1.40 t

where: Im (tCO2e) is the GHG emissions in infra- N2O ) from the IPCC (1996), we can obtain the carbon structure material production; n is the number of build- emissions; see Equation 3. 3 ing materials and elements; qi (t or m )is the amount of n material i; wi(%) is a proportion for waste of material E0= / e i # Ej i= l Equation 3 i produced during the erection; EFCO2,i (g/t) is the

CO2 emission factor in the material i production phase;

EFCH4,i (g/t) is the CH4 emission factor in the mate- where: E0 (TJ) is annual energy burdens of electrical

rial i production phase; and EFN2O,i (g/t) is the N2O equipments; n is the number of types of electrical equip-

emission factor in the material i production phase. ment in site; Ej is the number of equipment j; Ej (kwh) is the annual electricity consumption of equipment j. Construction During the maintenance phase, we mainly consider The GHG emissions of construction phase includes two the emissions from the materials production and the parts: carbon emissions from the construction process road repairing. The materials used in maintenance and transportation of construction materials, which include cement, sand gravel and asphalt. The energy mainly covers shipping of materials from manufactur- for road repairing is concluded to be 5% of total embod- ing site to construction sites as well as the transportation ied energy of the materials used in maintenance as the to landfills/recyclers [33]. construction phase.

386 Carbon Management (2011) 2(4) future science group GHG accounting for pubilc transport in Xiamen City, China Research Article

Decommissioning NOx, PM10 and SOx). The GREET model takes the This GHG emission of this phase mainly derives from 1 million BTU (British thermal unit) output in every the demolition phase. The decommissioning energy for stage as a standard and calculates the emissions and this study is calculated using 90% of the total energy in energy use of the stage. The model integrates the emis- construction stage [39]. sions and energy use of all stages in order to get the final results from well-to-wheel. Disposal & recycling The waste construction material can be divided into recov- Fuel carbon footprints: well-to-tank (WTT) erable and unrecoverable materials. As for unrecoverable In the GREET model, CO2 emission factor (g/106BTU materials, only the transportation of the materials from fuel output) is calculated by carbon balance method, the build site to disposal site can release carbon emissions. namely the carbon in the burning process fuel minus The disposal of recoverable materials includes the trans- the carbon in the combustion emissions as VOCs、CO portation as the unrecoverable materials and the reduced and CH4, and the remaining carbon is changed into emissions from the recycling phase; see Equation 4. CO2 can be calculated by Equation 5:

n n d i ##i i ##c i ^i h ## i c IW= / RD TW+ / 1- R d T 6 i= l i= l Densityj ' LHVj ##10 C_ratioj - CO2j,k = 0.27 Equation 4 =^VOCj,k # 0.85 + COj,k # 0.43 + CH4j,k # 0.75hG

Equation 5 Where: Id (t) is the carbon emissions from the disposal of waste construction materials; n is the number of types of waste construction materials; Wi (t) is the total Where: CO2 j k is the CO2 emission factor of fuel j weight of waste construction material i; Ri (%) is the in the combustion process with the combustion techno recycling ratio of waste construction material i; Di (km) logy k (g/106BTU); Densityj is the density of proc- is the average distance from the build site to recycling site ess fuel j; LHVj is the low calorific value of process of waste construction material i; di (km) is the transpor- fuel j; C_ratioj is the carbon content of process fuel tation distance from the build site to the end-disposal site j; VOCj k is the CO emission factor of fuel j in the combustion process with the combustion technology of waste construction material i; and Tc (tCO2e/t·km) is the carbon emissions per unit construction material by k (g/106BTU); CH4 j k is the CH4 emission factor of different type of shipping. fuel j in the combustion process with the combustion technology k (g/106BTU); 0.43 is the carbon content Calculating methodology of vehicle & fuel carbon of CO; 0.85 is the average carbon content of VOC footprints (GREET model) emissions; 0.75 is the carbon content of CH4; 0. The The carbon footprint of public transport vehicles is former technical parameters of fuel in this model are derived from two aspects: fuel and vehicles. The energy contained in the fuel-specs of the GREET model. consumption, pollutant emissions and capital invest- ment existed in all stages of the life cycle of the vehicle, Fuel carbon footprints: tank-to-wheel (TTW) so the vehicle operation phase is not the sole concern Direct emissions occur during the tank-to-wheel phase when we measure the carbon footprint of vehicle and of the fuel. GHG emissions per kilometer [12] are calcu- fuel. Only by implementing research on all the stages lated based on the consumption of each fuel type and of the full life cycle can we really compare the energy the CO2e emissions per liter of fuel. Equation 6 calculates saving and emission reduction effects of different vehi- emissions per km for different vehicle categories [40]. cles and fuel. In this part the GHGs regulated emissions, and energy use in transportation (GREET) model Nx,i developed by the Argonne National Laboratory is used EFKM,i = / ECx,i#^EF COC2,x +EF H4,x # 21 + EFN2 o,x ##310h x ; Ni E as a research simulation tool, which has been widely used in North America since 1995. In the study on Equation 6 energy use aspects, the GREET model includes calculation methods of total energy (energy in non-renewable and renewable sources), fossil fuels (petroleum, fossil Where EFKM,i (gCO2e/km) is the transport emis- natural gas and coal, together), petroleum, coal and nat- sions factor per distance of vehicle category i; ECx,I ural gas. The GREET model can calculate three main (litre/km) is the energy consumption of fuel type x

GHGs (CO2, CH4, N2O) emissions and five standard in vehicle category i; EFCO2,x (gCO2 /l) is the CO2 emissions (volatile organic compounds [VOC], CO, emission factor for fuel type x; EFCH4,x (gCO2e/l)

future science group www.future-science.com 387 Research Article Cui, Meng, Wang & Lin

Table 2. Carbon footprints of the infrastructure of n Vm= / q i ##^1+ wih ^EF COC2,i + EF H4,i ##21 + EFN2 O,i 310h the normal bus transit system. i= l Category GHG emissions Equation 8

(tCO2e per year) where: Vm (tCO2e/t) is the GHG emissions from Infrastructure material production 663,665.74 vehicle material production; n is the number of vehicle Infrastructure construction 36,513.25 materials and elements; qi is the amount of material Infrastructure maintenance 293,375.05 i; while the waste of material i produced during the Infrastructure decommissioning 29,864.96 manufacture is denoted by wi. EFCO2,i (g/t) is the Infrastructure recycling 82.73 CO2 emission factor in the material i production phase; Aggregate 1,023,625.81 EFCH4,i (g/t) is the CH4 emission factor in the material

i production phase; EFN2O,i (g/t) is the N2O emission

is the CH4 emission factor for fuel type x; EFN2O,x factor in the material i production phase.

(gCO2e /l) is the N2O emission factor for fuel type x; and Ni is the total number of vehicles in category i, Vehicles carbon footprints: assembly, disposal Nx,i is the number of vehicles in vehicle category i using & recycling (ADR) fuel type x. Owing to lack of related data in China, our study cal- The GHG emission per passenger trip for different culated that the emission related to a middle passen-

vehicle categories can be calculated by Equation 7: ger car assembly, disposal and recycling is 1.33 t CO2e according to the GREET (2.7) model [29]. EFKM,i # DDi EFP,i = Pz Vehicles carbon footprints: vehicle operation Equation 7 The vehicle operation phase is the same with the fuel Where EFP,i (g/passenger trip) is the transport emis- TTW phase on the basis of different life cycle. Therefore,

sions factor in vehicle category i; EFKM,i (gCO2e/km) we only need to calculate the carbon footprint once in is the emissions from vehicle category i; DDi (km/year) the fuel life cycle. is the total distance driven by vehicle category i; Pz (passenger trip) is the total passenger capacity of vehicle Results category i. On the basis of the carbon footprint calculation methods presented above, we individually calculate and ana- Vehicles carbon footprints lyze the carbon footprints of urban public transport In this article, the carbon footprint calculation of vehi- system in Xiamen city (NBT and BRT). cles has been divided into three parts: vehicle component production, vehicle operation and vehicle assembly and Carbon footprints of the NBT system disposal and recycling (ADR), based on the fundamental Carbon footprints of the infrastructure parameters of vehicles life cycle of GREET model. Infrastructure carbon footprints are annualized based on the life span of the project. This is owing to the fact Vehicles carbon footprints: vehicle that emissions from material production, transport, components production construction, decommissioning and recycling occurs at The processes of vehicle components production phase the beginning or the end of the infrastructure life cycle, are: the raw material recovery; raw materials transpor- while other direct emissions such as operation and main- tation and processing; and material production, fabrica- tenance are annual. Not annualizing the upstream and tion, and processing. The GHG emission in producing the downstream emissions would thus grossly overstate emis- materials and components can be calculated by Equation 8: sions in the first year and would not be compatible with

Table 3. Consumption and carbon emissions for the infrastructure construction materials of the normal bus transit system.

Material Consumption (t) Actual GHG emission (tCO2e) Commuted GHG emission (tCO2e) Cement (in concrete) 1,149,200.07 3,132,222.94 1,627,816.26 Sand 6,777,580.78 2,995,582.26 1,556,804.10 Gravel 12,605,079.63 1,857,081.17 965,125.09 Asphalt 474,736.96 17,555,453.66 9,123,569.27 Aggregate 25,540,340.03 13,273,314.71

388 Carbon Management (2011) 2(4) future science group GHG accounting for pubilc transport in Xiamen City, China Research Article

Table 4. GHG emissions for the materials transportation of normal bus transit system. Freight Origin Destination Materials transport Actual GHG emissions Commuted GHG † distance (km) (tCO2e) emission (tCO2e) Cement (in concrete) Longyan, Fujian Xiamen, Fujian 142 12,966.79 6,738.84 Sand Zhangzhou, Fujian Xiamen, Fujian 50 26,927.33 13,994.13 Gravel Zhangzhou, Fujian Xiamen, Fujian 50 50,079.98 26,026.57 Asphalt Maoming, Guangdong Xiamen, Fujian 1,012 38,175.27 19,839.69 Aggregate 128,149.37 66,599.23 †The distances were measured by Google map.

Table 5. Annual GHG emissions for the infrastructure maintenance of the normal bus transit system. Material Material amount Maintenance Material Material GHG Commuted Transportation Commuted per unit area (kg) area (m2) amount (t) emissions material GHG GHG emissions transportation GHG

(tCO2e) emission (tCO2e) (tCO2e) emissions (tCO2e) Cement (kg) 36.54 2,180,661 79673.50 78,876.77 40,992.26 898.98 467.20 Gravel (m3) 0.27 2,180,661 862707.37 381,302.85 198,163.09 3,427.54 1,781.29 Sand (m3) 0.13 2,180,661 462328.04 68,113.87 35,398.78 1,836.83 954.60 Asphalt (kg) 14.90 2,180,661 32497.95 974.94 506.68 2,613.27 1,358.12 Aggregate 529,268.42 275,060.80 8,776.62 4,561.21 the approach of monitoring annually emissions [40]. The materials [38]. According to the former results, the total carbon footprints of the NBT infrastructure was total GHG emissions for the construction phase were

20,472,516.20 tCO2e and the average carbon footprint 730,264.96 tCO2e. was 1,023,625.81 tCO2e per year based on a 20-year life span (Table 2). Materials production accounted for Infrastructure maintenance the majority of total GHG emission, approximately Table 5 shows that the annual commuted material 56.23% of the carbon footprint. The second highest car- GHG emissions of the NBT system infrastructure bon footprint is from maintenance activities, accounting maintenance were 275,060.80 tCO2e and the GHG for 24.90%. Construction and decommissioning were emissions emitted by the materials transportation responsible for 3.10 and 24.90% of the infrastructure were 4,561.21 tCO2e. As mentioned in methodology carbon footprint, respectively. section, the energy for road repairing was concluded to be 5% of total embodied energy of the materials Infrastructure material production used in maintenance as the construction phase. The Until the end of 2008, the road lengths of the NBT sys- GHG emissions of equipment and labor power for tem in Xiamen was approximately 3,115.23 km and the road repairing were 13,753.04 tCO2e. The sum of the public transport hub area, 147,834 m2. As the normal bus above three items were the total GHG emissions of did not have the exclusive right-of-way, the road distribu- infrastructure maintenance. tion rate was about 51.97% according to the passenger capacity statistics of Xiamen in between 2003–2008. Infrastructure decommissioning The total GHG emission of infrastructure material The carbon emissions of the decommissioning phase production of NBT system was 13,273,314.71 tCO2e were calculated by the 90% of the total construction in total, of which asphalt was the largest contributor, carbon emissions: 11,945.98 tCO2e. contributing approximately 68.74% to carbon emissions. The details of the data for the consumption and Table 6 The operation condition of the normal bus transit system in emissions of infrastructure materials are shown in Table 3. Xiamen city, China in 2009.

Infrastructure transport & construction Category Values Table 4 shows that the carbon emissions for the materi- Total road length 3115.23 km Vehicle numbers 2,551 als transportation phase was 66,599.23 tCO2e, of which the emissions for sand were the largest. In this study, Total passenger capacity per year 56,424.73 million the carbon emissions for the equipment and labor power Total operating distance per year 193,654,000 km Total carbon footprint per year 147,177.04 tCO e in the construction phase was 663,665.74 tCO2e by the 2

5% of the embodied energy of the required construction Direct carbon footprint per person 260.84 gCO2e/person

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Raw materials extraction Manufacture Use and maintenance Demolition Recycling and land filling 670,885.66 53,748.46 423,316.89 29,947.29 206.82

Infrastructure Infrastructure Infrastructure Infrastructure materials construction use and maintenance demolition Land filling 670,665.74 365,513.25 293,375.05 29,864.96

Fuel production Fuel use Fuel material Infrastructure 17,235.21 129,941.84 recycling 82.73 Vehicle Vehicle assembly- materials disposal–recysling Land filling 7,219.92 338.36 Transport

Figure 2. Carbon footprints flowchart of the normal bus transit system of Xiamen city, China in 2009 (tCO2e per year).

Carbon footprints of the vehicles the carbon footprint from the vehicle ADR phases was

Usually, the vehicle type of the NBT system is the same approximately 338.36 tCO2e. To conclude, the car- as the connecting line of the BRT system; therefore, bon footprint of the NBT system was approximately

the carbon footprints of materials productions were 72537.55 tCO2e. substituted for the average of the connecting line vehicles (XMQ6127G and XMQ6891G) of BRT system, Carbon footprints of the fuels in that, the carbon footprint from material production Gasoline and diesel fuels are used by the NBT system.

of every vehicle was 28.30 tCO2e [29]. There are 2551 Table 6 shows that the total carbon footprint of the buses of the NBT system in Xiamen city, China; in operation phase from the NBT system in Xiamen city

total the carbon footprint of materials production was in 2009 was 147,177.04 tCO2e, of which the direct

72,199.19 tCO2e. Based on the calculation methods, carbon footprint per capital was 260.84 gCO2e.

700,000 60 Carbon footprints of the NBT system in total 600,000 Figures 2 & 3 show the carbon 50 footprints of the NBT system in Xiamen city, China. Using

500,000 ) 40 2009 as an example, the result e

2 was 1,178,361.13 tCO e, among 400,000 2 which, the materials production, tC O 30 maintenance and vehicles opera- 300,000 entage rc (% Pe tion make up the top three con- 20 tributors to the carbon footprint, 200,000 responsible for 56.32, 24.90 and 12.49%, respectively. 10 100,000 Carbon footprints of the 0 0 BRT system

e n g Carbon footprints of ials ials uction the infrastructure Recyclin The total carbon footprints of the Vehicle ADR Road mater BRT infrastructure (Project I) was Vehicle operatio DecommissioninVehicleg mater Road maintenanc Road constr 2,101,871.28 tCO2e and the average carbon footprint was 42,037.43 Figure 3. Carbon footprints of the normal bus transit system of Xiamen city, China in 2009 tCO e per year based on a 50-year (tCO e per year). 2 2 life span (Figure 4). Since BRT roads ADR: Assembly, disposal and recycling. are mostly viaduct styles that the

390 Carbon Management (2011) 2(4) future science group GHG accounting for pubilc transport in Xiamen City, China Research Article usage period is 50 years compared with the NBT 20 years. Operation and maintenance activities 24,000 accounted for 55.49% of infrastructure total GHG emission. Materials production deducted the emission 20,000 reduction from recycling accounted for approximately 39.78% of total life cycle emission. Transport activi- 16,000 ties including shipping of materials from manufacturing site to construction site and the transportation 12,000 e to landfills/recyclers accounted for only approxi- 2 mately 0.36% of the total life cycle GHG emissions. tCO 8000 Construction and decommissioning were responsible for 2.30 and 2.07% of the infrastructure carbon 4000 footprint, respectively. Different from the NBT, cement, steel and sand 0 were the largest contributors to embodied energy and n g -4000 emission. The detailed data for the consumption and uction emissions of infrastructure materials have been listed in Operatio Recyclin Maintenance Constr a previous study [29]. The total GHG emission of infra- ial production Decommissioning Mater structure material production was 1,010,008.62 tCO2e and 20,200.1 tCO2e per year. It is worth noting that the BRT infrastructure operation phase includes the night-time view project (54%) Figure 4. Carbon footprints for the infrastructure of the bus rapid transit on the exclusive roads apart from the nights, elevators, system of Xiamen city, China in 2009 (tCO e per year). card readers and other electrical equipments (46%) at 2 Reproduced with permission from . bus station. There are some waste construction materi- [29] als (steel bars and aluminum profiles) of the BRT infrastructure, which can be protected for recycling. The Carbon footprints of the BRT system in total energy consumption in the re-machining process of the When compared with NBT system, Figure 6 showed recycled steel bars is 20–50% of the original produc- the total carbon footprint of the BRT in Xiamen City. tion; here we chose 40% for calculation. The recovery The total carbon footprint was 55,927.07 tCO2e per factor of the steel bars is 0.50. The energy consump- year. Infrastructure operation, infrastructure mate- tion of recycled aluminum profiles is 5–8% of original rial production, fuel consumption and infrastruc- production of aluminum and here 4% is acceptable. ture maintenance activities accounted for the first The recovery factor for aluminum is 0.95 [39,41]. The four parts of the total carbon footprints. Whereas distance from the building site to disposal site is 5 km other parts together merely represent 5.04% of the for the unrecoverable materials and 10 km for the total emissions. recoverable materials [39]. Vehicle material production, 801.25t, 5.77% Assembling–disposal– Carbon footprints of the vehicles and fuels recycling, Figure 5 showed that fuel consumption accounted for 29.18t, 0.21% the majority of total GHG emissions, approxiately 94.02% of the vehicle carbon footprint. Vehicle material production and ADR activities accounted for 5.77 and 0.21% of the total vehicle emission, respectively. According to the local statistics of buses by Xiamen Metal Recycling Company, a default retirement age of 10 years for vehicles was used in this article. There are two main kinds of vehicles of BRT system in Xiamen City, the trunk route vehicle (XMQ6127G) Fuel consumption, 13,059.21t, 94.02% and the feeder line vehicle (XMQ6891G). The configu- ration parameters of vehicles comes from the homepage Figure 5. GHG emissions of the vehicles and fuels of the bus rapid transit of Xiamen Kinglong Auto Group [102] and the ration of system of Xiamen city, China in 2009 (tCO e per year). vehicle materials are obtained by interview with work- 2 Reproduced with permission from [29]. ers in Xiamen Metal Recycling Plant.

future science group www.future-science.com 391 Research Article Cui, Meng, Wang & Lin

by the NBT system. If we took only 25,000 50 the direct carbon emissions of fuel consumption in the vehicle opera- 20,000 40 tion into consideration, the average carbon emission of the BRT system was approximately 149.08 g CO e 15,000 30 ) 2

per person, and 260.84 g CO2e from e 2 10,000 20 the NBT system, only accounting for tC O 23.35 and 12.49% of the related total life cycle carbon emissions, respec- 5000 10 entage rc (% Pe tively. Therefore, the per capita carbon footprint and per capita direct 0 0 carbon emissions of BRT system were lower than NBT system and the -5000 n n -10 ials ials effects of energy saving of BRT was more advantageous, which is related ucture use Vehicle ADR to the features of the BRT system ucture mater Infrastr Vehicle operatio ucture demolitioVehicle mater ucture recyclying such as large volume, energy-saving Road maintainenceucture construction and environment-friendly vehicle Infrastr Infrastr Infrastr Infrastr type and exclusive right-of-way.

Figure 6. Carbon footprints of the bus rapid transit system of Xiamen city, China, in 2009 Discussions &

(tCO2e per year). future perspective ADR: Assembly, disposal and recycling. After 2005, there was a big challenge facing the development of public Comparative analysis on the carbon footprint of transport in Xiamen city. In terms of the percentage the BRT systen and the NBT system of bus travel, although it is a high level in Xiamen city, Table 7 illustrated the carbon footprint analysis results there is still a wide gap between Xiamen city and the of the BRT and NBT system in Xiamen city in 2009. international level of 40–80%. NBT is still the main The average carbon emissions of the BRT system were public transport and the BRT is in its infancy. Owing

4.18 g CO2e per kilometer and 638.44 g CO2e per per- to the traffic congestion, the running speed public vehi- son based on the life cycle, comparing those of 6.08 cles dropped to 16 km/h at peak time. A lack of station

per kilometer and 2,088.38 g CO2e per person emitted facilities, inadequate transportation capacity access to the island and the single structure of transport serv- Table 7. A comparison list of carbon footprint from the bus rapid transit ices cannot satisfy needs to the travel long distances and the normal bus transit systems in Xiamen city, China, in 2009 of the Bay City. Therefore, there is an urgent need to

(tCO2e). adjust the public transport network architecture and Category BRT NBT construct the multilevel, large capacity and rapid public transport system. Infrastructure In the urban public transport system of Xiamen Materials production 20,200.17 663,665.74 City, if we only consider the direct carbon emissions Construction 1,107.57 36,513.25 of fuel consumption in the vehicle operation, the aver- Operation 17,273.74 age per capital carbon emission of the BRT system Maintenance 6,055.29 293,375.05 was approximately 149.08 gCO e, and 260.84 gCO e Decommissioning 870.42 29,864.96 2 2 from the NBT system, respectively. It is interesting Recycling -3,469.76 82.73 to find that the direct carbon emissions of fuel con- Vehicles and fuels sumption in the vehicle operation only accounted for Vehicle material production 801.25 7,219.92 23.35 and 12.49% of the total carbon footprint of Assembling, disposal and recycling 29.18 338.36 the BRT and NBT system. The emissions would be Vehicle operation 13,059.21 147,177.04 underestimated if ignoring other parts of emissions Aggregate 55,927.07 1,178,361.13 in the life cycle of the public transport system. This ） GHG emission (gCO2e/km 4.18 6.08 can be confirmed by the report of GHG Emissions ） GHG emission (gCO2e/person 638.44 2088.38 from the US Transportation Sector (1990–2003). BRT: Bus rapid transit; NBT: Normal bus transit. According to the EPA [31], the total life cycle

392 Carbon Management (2011) 2(4) future science group GHG accounting for pubilc transport in Xiamen City, China Research Article emissions for the US nation’s transportation sector gap existed between China and abroad. Future research are estimated to be 27–37% higher than direct fuel should focus on determining the parameters for China. combustion emissions. In future studies, the parameters selection of carbon Both the GHG emissions per km and per capita from footprint model should be focused on ensuring a result the BRT system were lower than the NBT system. The of accuracy and objectivity. At the same time, owing to reasons came from the larger volume and lower energy- the data accessibility, input-output assessment meth- consumption of the BRT system. Based on this study, odology is difficult to apply to real carbon footprint we can initially conclude that Xiamen should gradually calculation. Second, owing to limited time and data establish the low-carbon public transportation system sources, this article only made comparative analysis on which is dominated by the BRT and based on NBT. the carbon footprint of the BRT system and the NBT Carbon footprint assessment is a new measure to system. In the future, the research should be gradually account for the GHG emissions and still at the start- expanded to taxis, private cars and other vehicles. ing stage on the related studies of China. This article built upon the carbon footprint assessment frame of Financial & competing interests disclosure urban public transport system, which is a useful supple- This study was supported by Chinese Academy of Sciences ment for the transport carbon footprint methodology. (KZCX2-YW-450), International Cooperation Program of State Moreover we have evaluated the carbon footprint of the Commission of Science and Technology of China (2009DFB90120), two main public transport systems (NBT and BRT) by National Natural Science Foundation of China (No. 71003090) this model, expanding the research area and enriching and Public Welfare Project on Environment Protection (No. the research cases, as the best experience for other cities 201009055). The authors have no other relevant affiliations or in China. Some work remains to be further studied. financial involvement with any organization or entity with a finan- First, we chose the parameters on construction mate- cial interest in or financial conflict with the subject matter or materi- rials production, vehicles ADR and emission factors, als discussed in the manuscript apart from those disclosed. Writing which were referred to foreign literatures. In fact, some assistance was utilized from Marian Rhys of Simply better.

Executive summary Introduction This article built the carbon footprint assessment frame of urban public transport system and accounted for the GHG emissions of the two main public transport system (normal bus transit [NBT] and bus rapid transit [BRT]) by life cycle assessment methodology from three components as infrastructure, fuels and vehicles. Direct fuel GHG emissions

The average direct fuel GHG emissions of the BRT system was approximately 149.08 gCO2e per person and 260.84 gCO2e per person from the NBT system, only accounting for 23.35 and 12.49% of the related total life cycle carbon emissions, respectively. Indirect GHG emissions The indirect emissions mainly come from energy consumption by the life cycle of infrastructure, vehicles and the upstream process of fuel, of which the largest emissions share of BRT system was concentrated in the upstream material production activities of both infrastructure and vehicles, which accounted for 31.33% of the total carbon footprint and the largest carbon emission contributor to NBT system is the material extraction activities, accounting for 56.60; road maintenance the second largest contributor 24.90%. Comparative analysis The per capita carbon footprint and per capita direct carbon emissions of BRT system were lower for the NBT system and the effects of energy saving of BRT was more advantageous, which is related to the features of the BRT system such as large volume, energy-saving and environment-friendly vehicle type and exclusive right-of-way. Police relevance Xiamen city should gradually establish the low-carbon public transportation system which was dominated by the BRT system and based on the NBT system.

Bibliography 2 Fuglestvedt J, Berntsen T, Myhre G, Rypdal K, n n Study on the transport carbon footprint. Papers of special note have been highlighted as: Skeie RB. Climate forcing from the transport 4 Bellasio R, Bianconi R, Corda G, Cucca P. sectors. PNAS 105, 454–458 (2008). n of interest Emission inventory for the road transport

n n n n of considerable interest Study on the transport carbon footprint. sector in Sardinia (Italy). Atmos. Environ. 41, 677–691 (2007). 1 Yan X, Crookes RJ. Reduction potentials of 3 Huang Y, Bird R, Bell M. A comparative energy demand and GHG emissions in study of the emissions by road maintenance n n Study on the transport carbon footprint. China’s road transport sector. Energy Policy works and the disrupted traffic using life cycle 5 Hensher DA. Climate change, enhanced 37, 658–668 (2009). assessment and micro-simulation[J]. GHG emissions and passenger transport – Transportation Research Part D. Transp. & n n Study on the transport carbon footprint what can we do to make a difference? Environ. 14, 197–204 (2009).

future science group www.future-science.com 393 Research Article Cui, Meng, Wang & Lin

Transportation Research Part D –Transport & 15 Somner J, Scott K, Morris D, Gaskell A, n Introduction of carbon footprint research on Environment. 13(2), 95–111 (2008). Hepherd I. Ophthalmology carbon the BRT system. footprint: something to be considered? J. n n Study on the transport carbon footprint. 24 Estupinan N, Rodriguez DA. The Cataract Refractive Surgery 35, 202–203 6 Singh A, Gangopadhyay S, Nanda PK, relationship between urban form and station (2009). Bhattacharya S, Sharma C, Bhan C. Trends of boardings for Bogota’s BRT. Transportation GHG emissions from the road transport sector n n Useful review of carbon footprint Research Part A – Policy & Practice 42, in India. Sci. Total Environ. 390, 124–131 assessment methodology. 296–306 (2008).

(2008). 16 Kenny T, Gray NF. Comparative n Introduction of carbon footprint research on performance of six carbon footprint models n n Study on the transport carbon footprint. the BRT system. for use in Ireland. Environ. Impact Assessment 7 Steenhof P, Woudsma C, Sparling E. GHG 25 Golotta K, Hensher DA. Why is the Brisbane Rev. 29, 1–6 (2009). emissions and the surface transport of freight bus rapid transit system deemed a success? in Canada. Transportation Research Part D – n n Useful review of carbon footprint Road & Transport Res. 17, 3–16 (2008). assessment methodology. Transport & Environment 11,369–376 (2006). n Introduction of carbon footprint research on

n n Study on the transport carbon footprint. 17 Friedrich E, Pillay S, Buckley CA. Carbon the BRT system. footprint analysis for increasing water supply 8 Matthews HS, Hendrickson CT, Weber CL. 26 Abdelghany KF, Mahmassani HS, and sanitation in South Africa: a case study. The importance of carbon footprint Abdelghany AF. A modeling framework for J. Cleaner Prod. 17,1–12 (2009). estimation boundaries. Environ. Sci. & bus rapid transit operations evaluation and Technol. 42,5839–5842 (2008). n n Useful review of carbon footprint service planning. Transportation Planning & assessment methodology. Technol. 30, 571–591 (2007). n n Study on the transport carbon footprint.

18 Klemes J, Pierucci S. PRES 2007: carbon n Introduction of carbon footprint research on 9 Delucchi M, Mark A. Life cycle emissions footprint and emission minimization, the BRT system. model (LEM). Institute of Transportation integration and management of energy Studies, University of California, USA 27 William V, Jerram LC. The potential for BRT sources, industrial application and case (2003). to reduce transportation-related CO2 studies. Energy 33,1477–1479 (2008). emissions. Public Transportation. BRT Special n Inroduction of two transportation life n n Useful review of carbon footprint Edition 219–237 (2006). cycle models. assessment methodology. n Introduction of carbon footprint research on 10 Burnham A, Wang M, Wu Y. Development 19 Perry S, Klemes J, Bulatov I. Integrating waste the BRT system. and applications of GREET 2.7 – the and renewable energy to reduce the carbon transportation vehicle-cycle model. Argonne 28 Wohrnschimmel H, Zuk M, footprint of locally integrated energy sectors. National Laboratory, Chicago, USA (2006). Martinez-Villa G et al. The impact of a bus 10th conference process integration, modeling rapid transit system on commuters’ exposure n Inroduction of two transportation life and optimization for energy saving and to Benzene, CO, PM2.5 and PM10 in cycle models. pollution reduction. Ischia Isl. 38(10, Mexico City. Atmos. Environ. 42, 11 Wiedmann T, Minx J. A definition of 1489–1497 (2007). 8194–8203 (2008).

‘carbon footprint’. SA Research & n n Useful review of carbon footprint n Introduction of carbon footprint research on Consulting. 9 (2007). assessment methodology. the BRT system. n The most complete definition of 20 Zachary J. Options for reducing a coal-fired 29 Cui SH. Carbon footprint analysis of the bus carbon footprint. plant’s carbon footprint, Part II. Power rapid transit (BRT) system: a case study of 12 Druckman A, Jackson T. The carbon 152(7), 50,52,54,55 (2008). Xiamen City, China. Int. J. Sustainable

footprint of UK households 1990–2004: a n n Useful review of carbon footprint Develop. & World Ecol. 17(4), 329 – 337 socio-economically disaggregated, quasi- assessment methodology. (2010). multi-regional input-output model. 21 Christen K. The carbon footprint of n Introduction of carbon footprint research on Ecological Economics 68, 2066–2077 (2009). transportation fuels. Environmental Sci. the BRT system. n n Useful review of carbon footprint Technol. 41,6636–6636 (2007). 30 Carbon Trust, DEFRA and BSI. Guide to assessment methodology. n n Useful review of carbon footprint PAS 2050 How to assess the carbon footprint 13 Barthelmie RJ, Morris SD, Schechter P. assessment methodology. of goods and services. London, England Carbon neutral biggar: calculating the 22 Wang W. Study on low carbon development (2008). community carbon footprint and renewable of public transport in Xiamen based on n n Determination for carbon footprint research energy options for footprint reduction. carbon footprint assessment [master’s thesis]. boundary of normal bus transit (NBT) and Sustainability Sci. 3, 267–282 (2008). Xiamen, China: Institute of Urban BRT system. n n Useful review of carbon footprint Environment, Chinese Academy of 31 EPA. GHG Emissions from the US assessment methodology. Sciences(In Chinese) (2010). Transportation Sector,1990–2003.

14 Cole A .More treatment in surgeries and at n Introduction of carbon footprint research on Washington, DC, USA:US Environmental home will help cut NHS carbon footprint. the bus rapid transit (BRT) system. Protection Agency Office of Transportation BMJ 338 (2009). 23 Bitterman A, Hess DB. Bus rapid transit and Air Quality 2006.

n n Useful review of carbon footprint identity meets universal design. Disability & n n Determination for carbon footprint research assessment methodology. Soc. 23(5), 445–459 (2008). boundary of NBT and BRT system.

394 Carbon Management (2011) 2(4) future science group GHG accounting for pubilc transport in Xiamen City, China Research Article

32 Carpenter AC, Gardner KH, Fopiano J, 36 Asif M, Muneer T, Kelley R. Life cycle Projects’[R]. United Nations Framework Benson CH, Edil TB. Life cycle based risk assessment: a case study of a dwelling home in Convention on Climate Change 1–46 assessment of recycled materials in roadway Scotland. Building & Environment. 42, (2006). construction. The 6th International 1391–1394 (2007). n n Very important parameter sources. Conference on Developments in the Re-Use of n GWP factors. Mineral Waste (Wascon 2006). Belgrade, 41 Yang J. Life-cycle energy consumption Serbia. 1458–1464 (2006). 37 Cole R J, Kernan PC. Life-cycle energy use in analysis of adsorption biodegradation office buildings. Building & Environment 31, activated sludge. Sichuan Environ. 21: 23 n n Determination for carbon footprint research 307–317 (1996). (2002). boundary of NBT and BRT system. n n Very important parameter sources. n n Very important parameter sources. 33 Huang Y, Bird R, Heidrich O. Development 38 Scheuer C, Keoleian GA, Reppe P. Life cycle 42 Xiamen Communication Commission. of a life cycle assessment tool for construction energy and environmental performance of a Annual Report on the Development and maintenance of asphalt pavements. The new university building: modeling challenges of Transportation, Posts and 6th International Conference on Sustainable and design implications. Energy & Buildings Telecommunications of Xiamen City Aggregates, Pavement Engineering and 35, 1049–1064 (2003). in 2008 (2009). Asphalt Technology. Liverpool, England

283–296 (2007). n n Very important parameter sources. Websites n n Determination for carbon footprint research 39 Qiao YF. Studies on energy consumption of 101 Xiamen Bus Rapid Transit system boundary of NBT and BRT system. traditional dwelling houses based on life cycle assessment [master’s thesis]. Xi’an, China: construction project. 34 IPCC/OECD/IEA. IPCC Guidelines for Xian University of Architecture and www.xmbrt.com.cn/FirstIssue.asp National Greenhouse Gas Inventories.UK Technology.1–65. (In Chinese) (2006). 102 Xiamen Kinglong Auto Group Meteorological office, Bracknell, UK (1996). www.xmklm.com.cn/index.jsp n n Very important parameter sources. n Global-warming potential (GWP) factors. 40 UNFCCC/CCNUCC. Approved baseline 35 Scheuer C, Keoleian GA, Reppe P. Life cycle methodology AM0031 ‘Baseline energy and environmental performance of a Methodology for Bus Rapid Transit new university building: modeling challenges and design implications. Energy & Buildings 35, 1049–1064 (2003). n Global-warming potential (GWP) factors.

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