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Life cycle assessment of yard tractors using hydrogen fuel at the Port of Kaohsiung, Taiwan
Energy 189 (2019) 116222
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Life cycle assessment of yard tractors using hydrogen fuel at the Port of Kaohsiung, Taiwan Ching-Chih Chang a, *, Po-Chien Huang b, Jhih-Sheng Tu b a
Department of Transportation and Communication Management Science and the Research Center for Energy Technology and Strategy, National Cheng Kung University, No. 1, University Road, Tainan, 70101, Taiwan b Department of Transportation and Communication Management Science, National Cheng Kung University, No. 1, University Road, Tainan, 70101, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 April 2019 Received in revised form 9 September 2019 Accepted 25 September 2019 Available online 25 September 2019
The purpose of this study is to use LCA to evaluate different fuel usage in yard tractors, which include diesel, electric, LNG, and hydrogen fuel cells. This study refers to ISO regulations to assess the investigation. Empirical results show (1) for the diesel yard tractor, the total carbon emissions is 43,870.60 kgCO2e, and the carbon footprint is 6.40106 kgCO2e/TK. The hotspot is the usage stage (76.83% of the total emissions); (2) for the electric yard tractor, the total carbon emissions is 16,563.63 kgCO2e, and the carbon footprint is 2.42106 kgCO2e/TK. The major emission hotspot is the raw material stage (96.15% of the total emissions); (3) for the LNG yard tractor, the total carbon emissions is 33,560.09 kgCO2e, and the carbon footprint is 4.89106 kgCO2e/TK. The main emissions hotspot is the usage stage (85.04% of the total emissions); (4) for the hydrogen yard tractor, the total carbon emissions is 13,709.87 kgCO2e, and the carbon footprint is 2.00106 kgCO2e/TK. The biggest emission’s hotspot is the raw material stage (95.32% of the total emissions). The results demonstrate that the better fuel alternative to use for yard tractors is hydrogen, which has the greatest effect on GHG mitigation, followed by electric and LNG. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Life cycle assessment Carbon footprint Green port LNG Hydrogen
1. Introduction Based on the statistics released by the World Bank (2018) [1], global GDP has shown a positive growth between 2005 and 2017, except for the years of 2008 and 2009 in which a financial tsunami broke out, and growth is predicted to recover in 2017e2019. In addition, the International Monetary Fund (IMF, 2018) [2]estimated the growth rates of 2017 and 2018 in global economy could reach to around 3.7%, and Taiwan would see an increase of around 2.9% and 2.7%, respectively. Generally, international trade is one of the engines derived from global economic growth. The main forms of freight for international trade involve ocean shipment, air transport, and railroad transport. According to the Review of Maritime Transport released by the United Nations Conference on Trade and Development (UNCTAD) in 2017, goods transported internationally by sea accounted for about 80% of overall trade volume in 2016, an increase of 2.6% over 2015. A 3.2% annual rise is also predicted from 2017 to 2022, indicating that
* Corresponding author. E-mail addresses: [email protected] (C.-C. Chang), pchuang99tw@gmail. com (P.-C. Huang), [email protected] (J.-S. Tu). https://doi.org/10.1016/j.energy.2019.116222 0360-5442/© 2019 Elsevier Ltd. All rights reserved.
the development of the global economy highly relies on maritime transport and that the growth would continue year after year in the future. The International Monetary Fund (2018) [2] and Review of Maritime Transport released by the UNCTAD (2018) [3] reported global GDP is expected to grow by more than 3.0% and 3.8% over the 2018e2023 period, respectively. The Review of Maritime Transport released by the UNCTAD (2017) [4] indicated that container trade went up 14.94% from 1980 to 2016. The volume of maritime trade surged as a result of busing operations at sea ports. Nowadays, most of the container-handling and transport equipment at port still uses diesel for fuel. During operation, (especially yard tractors) they release large volumes of greenhouse gases and toxic substances, especially diesel particulate matter (DPM). The California Air Resources Board (CARB) has pointed out that the exhaust discharged from the use of diesel for fuel contains toxic substances, among which DPM is the main pollutant. According to data from CARB, the toxic air pollutant can increase cancer risk by 70%, and it is probably a principal cause of lung cancer, including lung adenocarcinoma. The Environmental Protection Agency’s (EPA, 2009) [5] Current Methodologies in Preparing Mobile Source Port-Related Emissions Inventories indicates that the main sources of greenhouse gases in
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harbor areas include commercial vessels, harbor vessels, container handling equipment, locomotives in harbor areas, and motor vehicles going in and out of harbors. These five sources could have a rather large environmental impact on harbors and the surrounding areas. In response, all major ports around the world have started to establish concrete measures to reduce emissions from the above mentioned sources of pollution. The most famous is the San Pedro Bay Port Clean Air Action Plan, which was announced in 2006 to set emissions standards at the two largest ports, the Port of Los Angeles and the Port of Long Beach. It was suggested in the San Pedro Bay Ports Clean Air Action Plan that the machine equipment applied in harbor areas could use alternative fuels or fuels with higher efficiency, or the engines of such equipment could be changed in order to reduce the amounts of toxic exhaust emitted. The annual report of the Port of Long Beach and the Port of Los Angeles presented the Technology Advancement System (TAP) in 2013 and proposed to use new shortdistance trucks and tractors running on batteries or hydrogen fuel cells to achieve the goal of green ports. Previous literature has applied life cycle assessment and carbon footprint to study the power sources of transportation and which method could save more energy and further reduce carbon emissions. (Zhang et al., 2017 [6]; Chang et al., 2016 [7]; Hwang, 2013 [8]; Arteconi et al. (2010) [9]). The findings of the study indicated that the use of hydrogen, energy could lower carbon emissions effectively (Bicer and Dincer, 2018 [10]; Castellani et al., 2018 [11]; Chang et al., 2016 [7]; Pereira et al., 2014 [12]; Wang et al., 2013 [13]; Arteconi et al., 2010 [9]). According to the statistics from Taiwan International Ports Corporation Ltd., (2017) [14] the tonnage of container handled in Taiwan in 2016 totaled 733,560,000 metric tons, indicating a 21.10% growth from 2009 to 2016. In the meantime, the container traffic in 2016 amounted to 531,287,000 shipping tons, making up the largest portion (72.43%) of the entire tonnage of container handled, and one important aspect in container handling is the use of yard tractors (truck tractors) to transport containers to and from the dock. Most of yard tractors in the world transport containers to and from the dock use diesel for fuel. They travel at low speeds and often remain idling while waiting for long periods of time on the dock. As a result, they emit considerable amounts of greenhouse gases and air pollutants which can cause cancer. Literature regarding the greenhouse gas emissions polluted by the yard tractors at port, pointed out that yard tractors were one of the main sources of carbon emissions on container docks and the carbon emissions from such vehicles were closely associated with importation/exportation (Yu et al., 2017 [15]; Villalba and Gemechu, 2011 [16]). And Villalba and Gemechu (2011) [16] further indicated that natural gas combustion was the biggest inland emissions source, which was followed by diesel and electric, respectively. They suggest that port authorities ought to improve their dock management to reduce carbon emissions. For this reason, this paper intends to analyze the use of alternative fuels to reduce emissions of toxic gases in harbor areas. The Port of Kaohsiung is an example to study this kind of issue. This should be a benchmark for ports managers in the world. Life cycle assessment and carbon footprint analysis are adopted to study the total exhaust emissions from yard tractors running on diesel and the ones using alternative fuels, and the carbon footprint difference between them, as well as to analyze the emissions hotspot of different types of fuel. Four ISO standards, namely ISO 14040:2006 [17] Environmental Management – Life Cycle Assessment – Principles and Framework; ISO 14044:2006 [18] Environmental Management – Life Cycle Assessment – Requirements and Guidelines; ISO 14064e1:2006 [19] Greenhouse gases – Part 1:
Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals; and ISO/TS 14067:2013 [20] Greenhouse gases – Carbon footprint of products – Requirements and guidelines for quantification and communication are applied to evaluate the carbon footprint throughout the life cycle of different fuels from cradle to grave. Tonkilometer is adopted as the functional unit. (The primary data are acquired from related businesses, and the secondary data come through SimaPro 8.0.) With all the above-mentioned combined, the objectives of this study include the following: (1) To examine the total emissions and carbon footprint of yard tractors using diesel and those using alternative fuels (electric, liquefied national gas, and hydrogen fuel cells) during the life cycle and to analyze the carbon footprint using tonkilometer as the functional unit (2) To establish the differences in emissions of greenhouse gases from the use of dissimilar fuels and emissions hotspot through carbon footprint comparison and analysis and to provide the results to related units for reference This paper is divided into five chapters. The first three chapters are the introduction, literature review and study methods, respectively. Chapter IV describes the process and outcome of the empirical analysis, and the conclusions and suggestions are in Chapter V. 2. Research methods This study analyses the carbon footprint of yard tractors at the Port of Kaohsiung. Consequently, we first interpret relevant ISO standards; then we explain the data source and the scope definition, followed by designing the process diagrams for four kinds of yard tractors; and finally we determine the variables and constructs definitions, and then the quantitative models are used to evaluate carbon footprint. 2.1. ISO standards 2.1.1. ISO 14040:2006 environmental management, life cycle assessment, principles, and framework The elements specified in ISO 14040:2006 [17] for the production system are depicted in Fig. 1. In this product system, one should describe the system boundaries to verify to what extend one needs to study. To be specific, the basic framework of life cycle assessment in this study contains the steps from the extraction of raw materials, the manufacturing, the final product, the usage, and finally the recycling, reusage or disposals. All these steps can be linked up by the transportation and utility input. For the usage scenario, this study focuses on the yard tractors that served for one-year trucking.
System Boundary
Utility Input
Recycle and Reuse Materials
Manufactuing
Products
Use Disposals
Transportations
Fig. 1. The system boundary.
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During this period, the element inputs will be the fuels, the clean water, and the maintenance. 2.1.2. ISO 14044:2006 environmental management, life cycle assessment, requirements, and guidelines This study also applied the standard of ISO14044:2006 [18], which describes the name and the function of the product system, the functional unit, the system boundary, the sequence of allocation, the relevant assumptions, the quality of the activity data, the methods and categories of the life cycle impact assessment, the research restrictions, and lastly the results. 2.1.3. ISO 14064e1:2006 greenhouse gases – part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals ISO 14064e1:2006 [19] identified the scope of what is important when calculating greenhouse gas emissions at the organizational level. The scopes are as follows, and those of Scope I and Scope II are covered. (1) Scope I emissions: Identify the direct emissions which are from factories owned by the respective organizations, which include coal combustion from burning boilers, power generators, gas, and air conditioners. (2) Scope II emissions: Identify the indirect emissions which are from electric, heat, and vapors that are purchased from outside. (3) Scope III emissions: These are the other emissions that are neither in Scope I nor in Scope II. For example, the emissions that came from employees’ commuting or the emissions produced by other organizations.
2.1.4. ISO/TS 14067: 2013 greenhouse gases d carbon footprint of products d requirements and guidelines for quantification and communication ISO/TS 14067:2013 [20] inherited the specifications of ISO 14040:2006 [17] and ISO 14044:2006 [18]. Correspondingly, ISO/TS 14067:2013 [20] emphasized that the contributions of carbon dioxide are equivalent to the global warming potential instead of describing the contributions of other impacts or discussing the problems based the social level or economic level. There are two types of carbon footprints under the standard of ISO 14064e1:2006 [19] and ISO/TS 14067:2013 [20]. The differences between these two types are listed in Table 1 below: 2.2. The scope of operations and research data The carbon footprint evaluation aims at a forwarder which ran the trucking business with 40-foot container at the Port of Kaohsiung. This paper collected activity data based on the process diagram since this research is using the approach of the activity data multiplied by GHG emissions or removal factors to evaluate the
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carbon footprint, in this paper the impact assessment refers to the global warming potential (GWP100) from the IPCC (2013) [21]. In addition, we refer to the GHG emissions factors from the Simapro 8.0 database and the Carbon Footprint Calculation Platform set up by the Environmental Protection Administration of Taiwan. The functional unit was represented by ton-kilometers. The system was from cradle to grave, which contained the utility and the maintenance from the extraction of the raw materials, the manufacturing, and the trucking service to the disposal of the yard tractors in 2015. The trash produced by the yard tractor drivers was included as well. This study excluded several emissions sources from the trucking service: including capital goods such as the office building, the parking lot, the maintenance plant, the infrastructure of the port, the gas station, the charging station, the LNG filling station, and the body of the yard tractor. And, the calculation also omitted the emissions from the administration staff. 2.3. The process diagram of the yard tractors This paper was designed the process diagrams of four different yard tractors. As illustrated in these diagrams, the utility contains the fuels, the clean water, and the refrigerant; while, the maintenance was narrowed down to regular maintenance and unexpected maintenance. The disposals were referred to the manual of the Example Industrial Waste Disposal Plan for Land transportation, Water transportation and Support Activities for Transportation published by the Environment Protection Administration (2013) [22]. We then illustrate the process diagrams in detail in the following sections. 2.3.1. The process diagram of the diesel yard tractors The inventory of the diesel yard tractor was achieved as follows. First, the secondary data of the extraction of raw materials and manufacturing can be narrowed down to the utility input and the maintenance suppliers. Maintenance can be divided into regular maintenance and unexpected maintenance. Second, the container trucking contains the diesel fuel consumptions and refrigerant. Generally, the forwarder provides primary data, such as the consumption volume of fuel and the maintenance schedule, and its item list during trucking. Third, the disposals cover the energy consumption and maintenance when recycling and disposing of waste. All these things are illustrated in Fig. 2 below. 2.3.2. The process diagram of the electric yard tractors The inventory of the electric yard tractor was obtained as follows. First, the extraction of raw materials and manufacturing can be narrowed down to the utility input and maintenance supplies. We referred to the maintenance schedule on the Leaf service and maintenance guide released by the Nissan Motor Corporation (2012) [23]. Second, container trucking contains the electric consumption and refrigerant. Third, disposals cover energy consumption and maintenance when recycling and disposing of waste. All these things are shown in Fig. 3.
Table 1 Comparisons between two types of carbon footprints. Greenhouse gases at the organizational level To quantify Scope I emissions and Scope II emissions only To cover emissions of the six main greenhouse gases: CO2, CH4, N2O, PFCS, HFCS, and SF6
Carbon footprint of products
To quantify all three scope emissions To include six main greenhouse gases and the controlled substance listed in the Montreal Protocol Except for the CO2 from the combustion of the biomass/biofuels To cover all the greenhouse gases from the combustion of the fossil fuels and biomass/biofuels The electric generated at the target organization and then sold to other factories is counted as The electric generated at the target organization and then sold to other one of the scope I emissions factories should be excluded
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The Process Diagram of The Diesel Yard Tractor Extraction of raw materials and Manufacturing
Use (Trucking)
Disposals
Maintenance supplies Regular maintenance Clean water, Grease, Engine oil, Oil filter, Air filter, Gear core, Brake fluid, Gear oil Unexpected maintenance Tank, Quartz bulb, Turn signal flasher, Fence, Front supporting frame, Clutch operating cylinder, ip6m/m quick coupling, Former car fenders, Air suspension bags, Automatic circuit breaker, Dual wick lamp, JOST wooden disc springs, Muffler holder, Muffler beam Utility Input Material flow Energy flow Maintenance
Diesel refining Refrigerant Water purification
Gas station Dealer Water plant
Cargo trucking
Maintenance plants In the shop Incineration plant
Inspection Repairs
Disposal
Washing
Waste water
Landfill Recycling plant
Leave
Fig. 2. The process diagram of the diesel yard tractor.
The Process Diagram of The Electric Yard Tractor Extraction of raw materials and Manufacturing
Use (Trucking)
Disposals
Maintenance supplies Regular maintenance Clean water, Grease, Gear core, Brake fluid, Gear oil
Cargo trucking Maintenance plants In the shop
Incineration plant
Inspection Utility Input Material flow Energy flow Maintenance
Electricity generating
Power station
Refrigerant
Dealer Water plant
Water purification
Repairs
Disposal
Washing
Waste water
Leave
Landfill Recycling plant
Fig. 3. The process diagram of the electric yard tractor.
depicted in Fig. 5 below.
2.3.3. The process diagram of the LNG yard tractors The inventory of the LNG yard tractor contains the following. First, the extraction of raw materials and manufacturing can be narrowed down to the utility input and maintenance supplies. We referred to the maintenance information of the manual of engines maintenance provided by Cummins Westport Incorporation (2015) [24]. Second, container trucking contains the LNG consumptions and refrigerant. Third, disposals cover energy consumption and maintenance when recycling and disposing of waste. All these items are illustrated in Fig. 4 below.
2.4. The variables definition and the model construction
2.3.4. The process diagram of the hydrogen yard tractors The inventory of the hydrogen yard tractor is described as follows. First of all, the extraction of raw materials and manufacturing can be narrowed down to the utility input and maintenance supplies. We estimated the maintenance information based on the suggested maintenance schedule of the Tucson provided by Hyundai Motor Corporation (2010) [25]. Second, container trucking contains the liquefied hydrogen consumptions and the refrigerant. Third, disposals cover the energy consumption and maintenance when recycling and disposing of waste. All these things are
2.4.1. Variables definition The basic concept for this calculating model is the tons of the container multiplied by the container volume, then multiplied by the transportation distance to get the total carbon emissions. For further discussion, we have listed several assumptions here, in which the tons of a container weigh the maximum weight of a 40foot container carrier, the container volume was approximately estimated to be 16,000 in 2015, and the transportation distance was presented by the average transport distance of a forwarder at port number 43 in 2015. Therefore, the inventory results can be revealed by the total carbon emissions or by the per ton-kilometers carbon
2.3.5. Fuel efficiency and emission factors of yard tractors The fuel efficiency and emission factor of the different types of yard tractors, including diesel yard tractors, electric yard tractors, LNG yard tractors and hydrogen yard tractors used in this study are presented in Table 2.
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The Process Diagram of The LNG Yard Tractor Extraction of raw materials and Manufacturing
Use (Trucking)
Disposals
Maintenance supplies Regular maintenance Clean water, Grease, Gear core, Brake fluid, Gear oil, Natural gas engine oils, Natural gas filters, Sparkplug
Cargo trucking Maintenance plants In the shop
Gas liquification Refrigerant
Material flow Energy flow Maintenance
Water purification
Incineration plant
Inspection
Utility Input
Repairs
Disposal
Washing
Waste water
Filing station
Dealer Water plant
Landfill Recycling plant
Leave
Fig. 4. The process diagram of the LNG yard tractor.
The Process Diagram of The Hydrogen Yard Tractor Extraction of raw materials and Manufacturing
Use (Trucking)
Disposals
Maintenance supplies Regular maintenance Clean water, Grease, Engine oil, Oil filter, Air filter, Gear core, Brake fluid, Gear oil, Coolant core
Cargo trucking Maintenance plants In the shop
Utility Input Hydrogen generating
Material flow
Refrigerant
Energy flow Maintenance
Water purification
Incineration plant
Inspection
Gas station Dealer Water plant
Repairs
Disposal
Washing
Waste water
Leave
Landfill Recycling plant
Fig. 5. The process diagram of the hydrogen yard tractor.
Table 2 Comparisons between two types of carbon footprints.
Fuel Efficiency Emission Factor e Extraction Emission Factor e Usage
diesel yard tractors
electric yard tractors
LNG yard tractors
hydrogen yard tractors
2.43 km/L 0.760 2.730
11.54 kW h/hr 0.69 e
0.9125 km/L 0.343 2.234
16 km/kg 6.970 e
footprint. The variables and their definitions are presented in Table 3.
TKiloi ¼ TD CP CQ CFPi ¼
2.4.2. Model construction of carbon footprint Based on the standardized carbon footprint indicators, the carbon footprint calculating model is exhibited as the following equations (1)e(4):
TCEMi TKiloi
(3) (4)
3. Empirical analysis
TCEMi ¼
4 X 32 X 6 X
ACijk LCEFjkl GWPjkl
(1)
3.1. The carbon footprint of the diesel yard tractor
(2)
The total greenhouse gas emissions and the carbon footprint of the diesel yard tractor are recorded in Table 4 below. First, the total greenhouse gas emissions of the diesel yard tractor is 43,870.60 kgCO2e. The first three emissions sources were the diesel
j¼1 k¼1 l¼1
LCEFjkl ¼ AMEFjkl þ TUEFjkl þ WEFjkl
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Table 3 Variables for the carbon footprint of the yard tractors. Variables Definitions ACijk AMEFjkl TUEFjkl WEFjkl LCEFjkl GWPjkl TKiloi TD CP CQ TCEMi CFPi i
j k
l
The activity data The yard tractor i uses fuel j, and replaces the maintenance k. Extraction and manufacturing emissions factors The extraction of the fuel j, and the manufacture of the maintenance k, the emittance of the greenhouse l. The emissions factor of the yard tractor in the usage stage The consumption of the fuel j, and the replacement of the maintenance k, the emittance of the greenhouse l. The emissions factor of the disposals The disposal treatment of the fuel j, and the disposal treatment of the maintenance k, the emittance of the greenhouse l. The emissions factor of the life cycle The consumption of the fuel j, and the replacement of the maintenance k, the emittance of the greenhouse l. The global warming potential The global warming potential of the greenhouse gas l of the consumption of the fuel j, and the replacement of the maintenance k in the life cycle. Ton-kilometers The sum of the weight of a unit container multiplied by the transportation distance The transportation distance The average transportation distance of the yard tractor to transport a 40-foot container. Carrying capacity The maximum weight a 40-foot container can be carried The container quantity The container quantity that a forwarder deals with in 2015 The total carbon emissions throughout the life cycle The total carbon emissions of the yard tractor i. The carbon footprint The carbon footprint of the yard tractor i presented in ton-kilometers. i represents the categories of the yard tractors, i ¼ 1; 2; 3; 4. In which, i ¼ 1 represents the diesel yard tractor; i ¼ 2 represents the electric yard tractor; i ¼ 3 represents the LNG yard tractor; i ¼ 4 represents the hydrogen yard tractor. j represents the categories of the fuels, j ¼ 1; 2; 3; 4. In which, j ¼ 1 represents the diesel fuel; j ¼ 2 represents the electric power; j ¼ 3 represents the LNG; i ¼ 4 represents the liquefied hydrogen. k represents the items of the maintenance, k ¼ 1; 2; /; 32. In which, k ¼ 1 represents the grease; k ¼ 2 represents the gear core; k ¼ 3 represents the brake fluid; k ¼ 4 represents the gear oil; k ¼ 5 represents the air filter, /, k ¼ 31 represents the climate control air filter; and k ¼ 32 represents the core coolant. l represents the categories of the greenhouse gases, l ¼ 1; 2; /; 6. In which, l ¼ 1 represents the carbon dioxide (CO2); l ¼ 2 represents the methane (CH4), l ¼ 3 represents the nitrous oxide (N2O), l ¼ 4 represents the perfluorocarbons (PFCS), l ¼ 5 represents the chlorofluorocarbons (HFCS), and l ¼ 6 represents sulfur hexafluoride (SF6)
Table 4 The carbon footprint of the diesel yard tractor. Stages The raw materials and manufacturing of yard tractor The use of yard tractors (trucking)
Diesel refining Maintenance supplies Diesel Refrigerant
The disposals of yard tractors Life cycle carbon footprint (total carbon emissions) Carbon footprint per ton kilometers (kgCO2e/TK)
consumption in the usage stage of 33,703.70 kgCO2e (76.83%), the diesel refining of 9382.72 kgCO2e (21.39%), and the refrigerant in the usage stage of 372.80 kgCO2e (0.85%). In short, the diesel consumption in the usage stage (trucking service) is the highest emissions hotspot throughout the whole life cycle. Second, the carbon footprint per ton kilometers is 6.40 106 kgCO2e/TK.
3.2. The carbon footprints of the alternative fuel yard tractors 3.2.1. The carbon footprint of the electric yard tractor The total greenhouse gas emissions and the carbon footprint of the electric yard tractor are listed in Table 5 below. First, the total greenhouse gas emissions of the electric yard tractor is 16,563.63 kgCO2e. The first three emissions sources were the electric generating of 15,925.20 kgCO2e (96.15%), the refrigerant leakage in the usage stage of 372.80 kgCO2e (2.25%), and the disposals of 235.4865 kgCO2e (1.42%). Moreover, the electric in the usage stage does not generate any greenhouse gas emissions, which leads to a carbon
Carbon Footprint
Percentage (%)
9382.72 173.76 33,703.70 372.80 237.62 43,870.60 6.40 106
21.39 0.39 76.83 0.85 0.54 100.00
footprint of 0. Second, the carbon footprint per ton kilometers is 2.42 106 kgCO2e/TK. 3.2.2. The carbon footprint of the LNG yard tractor The total greenhouse gas emissions and the carbon footprint of the LNG yard tractor are shown in Table 6 below. First, the total greenhouse gas emissions of the LNG yard tractor is 33,560.09 kgCO2e. The first three emissions sources were the LNG consumption in the usage stage of 28,538.85 kgCO2e (85.04%), the LNG refining of 4381.06 kgCO2e (13.05%), and the refrigerant in the usage stage of 372.80 kgCO2e (1.11%). If we compare these results with the diesel ones, we will find out that the first three emissions sources were the same. Second, the carbon footprint per ton kilometers is 4:89 106 kgCO2e/TK. 3.2.3. The carbon footprint of the hydrogen yard tractor The total greenhouse gas emissions and the carbon footprint of the hydrogen yard tractor are revealed in Table 7. First, the total
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Table 5 The carbon footprint of the electric yard tractor. Stages The raw materials and manufacturing of yard tractor The use of yard tractors (trucking)
Carbon Footprint
Percentage (%)
Electric generating Maintenance supplies Electric Refrigerant
15,925.20 30.14 0.00 372.80 237.62 16,563.63 2.42 106
96.15 0.18 0.00 2.25 1.42 100.00
Carbon Footprint
Percentage (%)
NG liquefying Maintenance supplies LNG Refrigerant
4381.06 31.65 28,538.85 372.80 235.73 33,560.09
13.05 0.09 85.04 1.11 0.70 100.00
The disposal of yard tractors Life cycle carbon footprint (total carbon emissions) Carbon footprint per ton kilometers (kgCO2e/TK)
Table 6 The carbon footprint of the LNG yard tractor. Stages The raw materials and manufacturing of yard tractor The use of yard tractors (trucking) The disposal of yard tractors Life cycle carbon footprint (total carbon emissions) Carbon footprint per ton kilometers (kgCO2e/TK)
4:89 106
Table 7 The carbon footprint of the hydrogen yard tractor. Stages The raw materials and manufacturing of yard tractor The use of yard tractors (trucking)
Hydrogen liquefying Maintenance supplies Liquid hydrogen Refrigerant
The disposal of yard tractors Life cycle carbon footprint (total carbon emissions) Carbon footprint per ton kilometers (kgCO2e/TK)
greenhouse gas emissions of the hydrogen yard tractor is 13,709.87 kgCO2e. The first three emissions sources were the hydrogen liquefying of 13,068.75 kgCO2e (95.32%), the refrigerant leakage in the usage stage of 372.80 kgCO2e (2.72%), and the disposals of 235.89 kgCO2e (1.72%). Here we have adopted the analytical results of Hwang (2013) [8] and assumed that the hydrogen was from the methane reformation, which indicates that the greenhouse gas emissions of liquefied hydrogen in the usage stage is 0. From the above-mentioned analytical results, one will find out that the largest emissions source for the hydrogen yard tractor is hydrogen liquefying, which is similar to the electric yard tractor. Second, the carbon footprint per ton kilometers is 2.00 106 . 3.3. The benefits analysis of carbon footprint mitigation using alternative fuel yard tractors The histogram of the emissions normalizations of these four kinds of yard tractors is illustrated in Fig. 6 below. According to this histogram, both LNG and diesel consumption in the trucking stage are the largest hotspots for the LNG and diesel yard tractors, which accounts for 85.04% and 76.83%; the material fuel is the largest emissions source for both the electric yard tractor and the hydrogen yard tractor, which accounts for 96.15% and 95.32%, respectively If we address the carbon footprint using per ton-kilometers, we comprehend that all three types of alternative yard tractors have the benefit of greenhouse gas eliminations. These eliminations, listed from the highest to the lowest, are the hydrogen yard tractor of 4.40 106 kgCO2e (or 68.75%), the electric yard tractor of 3.98 106 kgCO2e (or 62.24%), and the LNG yard tractor of 1.51 106 kgCO2e (or 23.59%), all of which are shown in Table 8.
Carbon Footprint
Percentage (%)
13,068.75 32.43 0.00 372.80 235.89 13,709.87 2.00 106
95.32 0.24 0.00 2.72 1.72 100.00
3.4. Policy suggestions Based on the above-mentioned results, this paper proposes several policies, which are stated as follows. First, the diesel yard tractor should be equipped with carbon-reducing technology and the engine turned off when lying idle. The administration should advocate and promote eco-driving for both, thus eliminating the fuel combustion emissions in the stage of container trucking. Second, the authorities should introduce more efficient methods of energy-generating for the electric yard tractor and the hydrogen yard tractor to lessen greenhouse gas emissions. Third, the government should fund a more environmentally-friendly refrigerant
100% 90% 80% 70% 60% 50% 40% 30%
Disposal
20%
Trucking-maintenance
10% 0%
Trucking-fuel Material-maintenance
Diesel
Electric
LNG
Hydrogen
Material-fuel
Fig. 6. The percentage of life cycle emission of the yard tractors.
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Table 8 The comparison of the carbon footprint in each stage of life cycle. Stages Material and Manufacturing Use (trucking)
Fuels Maintenance supplies Energy Refrigerant
Disposals Carbon footprint per ton - kilometers (kgCO2e/TK)
Diesel (baseline)
Electric (difference)
LNG (difference)
Hydrogen (difference)
9382.72 173.76 33,703.70 372.80 237.62 6.40 106
þ6542.48 (þ69.73%) 143.62 (82.65%) 33,703.70 (100.00%) 0.00 (0.00%) 2.13 (0.90%) 3.98 106 (-62.24%)
5001.66 (53.31%) 142.11 (81.78%) 5164.85 (15.32%) 0.00 (0.00%) 1.89 (0.79%) 1.51 106 (-23.59%)
þ3686.03 (þ39.29%) 141.33 (81.34%) 33,703.70 (100.00%) 0.00 (0.00%) 1.72 (0.73%) 4.40 106 (-68.75%)
to substitute the moderate refrigerant for reducing the carbon emissions of the LNG yard tractor. 4. Conclusions and suggestions This paper conducted the life cycle assessment mentioned in several ISO standards to evaluate the carbon footprints of the yard tractors at the Port of Kaohsiung that use different fuels as power sources. The scopes are evaluated from cradle to grave and the functional units are based on per ton-kilometer. The main findings of this study are as follows: (1) For the diesel yard tractor, the total carbo 106 n emissions is 43,870.60 kgCO2e, and the carbon footprint is 6.40 106 kgCO2e/TK. In addition, the largest emissions hotspot is the fuel in the usage stage, which produces 33,703.70 kgCO2e that accounts for 76.83% of total emissions. (2) For the electric yard tractor, the total carbon emissions is 16,563.63 kgCO2e, and the carbon footprint is 2.42 106 kgCO2e/TK. Also, the major emissions hotspot is the fuel in the raw material stage, which generates 15,925.20 kgCO2e that accounts for 96.15% of total emissions. (3) For the LNG yard tractor, the total carbon emissions is 33,560.09 kgCO2e, and the carbon footprint is 4.89 106 kgCO2e/TK. Moreover, the main emissions hotspot is the fuel in the usage stage, which creates 28,538.85 kgCO2e that accounts for 85.04% of total emissions. (4) For the hydrogen yard tractor, the total carbon emissions is 13,709.87 kgCO2e, and the carbon footprint is 2.00 kgCO2e/ TK. Furthermore, the biggest emissions hotspot is the hydrogen liquefying, in the raw material stage, which yields 13,068.75 kgCO2e that accounts for 95.32% of the total emissions. After comparing the alternative fuel yard tractors with the traditional diesel one, the results have illustrated that all three types of alternative fuel yard tractors have the benefit of greenhouse gas mitigation. The greenhouse gas reductions of the electric yard tractor and LNG yard tractor are 62.24% and 23.59% less than the diesel yard tractor. However, the hydrogen yard tractor has the largest greenhouse gas reduction, which is 68.75% less than the emissions of the diesel yard tractor. Moreover, the usage stage of the hydrogen yard tractor is 100% less than that of the diesel yard tractor. According to the above-mentioned findings, this paper suggests that the diesel yard tractor at the Port of Kaohsiung should steadily be replaced by the hydrogen yard tractor which would help to achieve the goal of green harbor construction and economic development simultaneously. Acknowledgement The authors acknowledge the Ministry of Science and Technology, Taiwan, ROC for providing partial funding to support under contract numbers MOST 107-2410-H-006-076.
References [1] World Bank. Global economic prospects: divergences and risks. Retrieved from, https://openknowledge.worldbank.org/handle/10986/29801; 2018. [2] IMF. World economic outlook. Retrieved from, https://www.imf.org/external/ datamapper/NGDP_RPCH@WEO/OEMDC/ADVEC/WEOWORLD/IRQ; 2018. [3] Review of maritime transport. Retrieved from, https://unctad.org/en/ PublicationsLibrary/rmt2018_en.pdf; 2018. [4] Review of maritime transport. Retrieved from, https://unctad.org/en/ PublicationsLibrary/rmt2017_en.pdf; 2017. [5] Environment Protection Administration. Current methodologies in preparing mobile source port-related emission invenories. Retrieved from, https://www. epa.gov/sites/production/files/2016-06/documents/2009-port-inventoryguidance.pdf; 2009. [6] Zhang Y, Jiang H, Li J, Shao S, Hou H, Qi Y, Zhang S. Life cycle assessment and optimization analysis of different LNG usage scenarios. Int J Life Cycle Assess 2017:1e10. [7] Chang CC, Wu FL, Lai WH, Lai MP. A cost-benefit analysis of the carbon footprint with hydrogen scooters and electric scooters. J Hydrogen Energy 2016;41:13299e307. [8] Hwang JJ. Sustainability study of hydrogen pathways for fuel cell vehicle applications. Renew Sustain Energy Rev 2013;19:220e9. [9] Arteconi A, Brandoni C, Evangelista D, Polonara F. Life-cycle greenhouse gas analysis of LNG as a heavy vehicle fuel in Europe. Appl Energy 2010;87(6): 2005e13. [10] Bicer Y, Dincer I. Life cycle environmental impact assessments and comparisons of alternative fuels for clean vehicles. Resour Conserv Recycl 2018;132(1):141e57. [11] Castellani B, Rinaldi S, Bonamente E, Nicolini A, Rossi F, Cotana F. Carbon and energy footprint of the hydrate-based biogas upgrading process integrated with CO2 valorization. Sci Total Environ 2018;615:404e11. [12] Pereira SR, Fontes T, Coelho MC. Can hydrogen or natural gas be alternatives for aviation? A life cycle assessment. Int J Hydrogen Energy 2014;39(25): 13266e75. [13] Wang DW, Zamel N, Jiao K, Zhou YB, Yu SH, Du Q, Yin Y. Life cycle analysis of internal combustion engine, electric and fuel cell vehicles for China. Energy 2013;59:402e12. [14] Taiwan International Ports Corporation. Annual statistic report: 2015. Taiwan, ROC: Taiwan International Ports Corporation, Ltd.; 2017. Kaohsiung. [15] Yu H, Ge YE, Chen J, Luo L, Tan C, Liu D. CO2 emission evaluation of yard tractors during loading at container terminals. Transp Res D Transp Environ 2017;53:17e36. [16] Villalba G, Gemechu ED. Estimating GHG emissions of marine ports-the case of Barcelona. Energy Policy 2011;39(3):1363e8. [17] ISO 14040. Environmental management – Life cycle assessment – Principles and framework. 2006. [18] ISO 14044. Environmental management – Life cycle assessment – Requirements and guidelines. 2006. [19] ISO 14064-1. Greenhouse gases – Part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals. 2006. [20] ISO/TS 14067. Greenhouse gases d carbon footprint of products d Requirements and guidelines for quantification and communication. 2013. [21] IPCC. Climate change 2013: the physical science basis. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press; 2013. [22] Environmental Protection Administration. Carbon footprint calculation Platform. Retrieved from, https://cfp-calculate.tw/cfpc/WebPage/LoginPage.aspx; 2013. [23] Nissan Motor Corporation. 2013 Leaf service and maintenance guide. Retrieved from, https://owners.nissanusa.com/content/techpub/ ManualsAndGuides/NissanLEAF/2013/2013-NissanLEAF-service-maintenance-guide.pdf; 2012. 38. [24] Cummins Westport Incorporation. ISL G brochure, 6. Retrieved from, http:// www.cumminswestport.com/content/430/ISL%20G%204971499_0315.pdf; 2015. [25] Hyundai Motor Corporation. Hyundai Tucson: normal maintenance schedule. 2nd 2010 Retrieved from. http://www.htmanual.net/normal_maintenance_ schedule-409.html.
Contents lists available at ScienceDirect
Energy journal homepage: www.elsevier.com/locate/energy
Life cycle assessment of yard tractors using hydrogen fuel at the Port of Kaohsiung, Taiwan Ching-Chih Chang a, *, Po-Chien Huang b, Jhih-Sheng Tu b a
Department of Transportation and Communication Management Science and the Research Center for Energy Technology and Strategy, National Cheng Kung University, No. 1, University Road, Tainan, 70101, Taiwan b Department of Transportation and Communication Management Science, National Cheng Kung University, No. 1, University Road, Tainan, 70101, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 April 2019 Received in revised form 9 September 2019 Accepted 25 September 2019 Available online 25 September 2019
The purpose of this study is to use LCA to evaluate different fuel usage in yard tractors, which include diesel, electric, LNG, and hydrogen fuel cells. This study refers to ISO regulations to assess the investigation. Empirical results show (1) for the diesel yard tractor, the total carbon emissions is 43,870.60 kgCO2e, and the carbon footprint is 6.40106 kgCO2e/TK. The hotspot is the usage stage (76.83% of the total emissions); (2) for the electric yard tractor, the total carbon emissions is 16,563.63 kgCO2e, and the carbon footprint is 2.42106 kgCO2e/TK. The major emission hotspot is the raw material stage (96.15% of the total emissions); (3) for the LNG yard tractor, the total carbon emissions is 33,560.09 kgCO2e, and the carbon footprint is 4.89106 kgCO2e/TK. The main emissions hotspot is the usage stage (85.04% of the total emissions); (4) for the hydrogen yard tractor, the total carbon emissions is 13,709.87 kgCO2e, and the carbon footprint is 2.00106 kgCO2e/TK. The biggest emission’s hotspot is the raw material stage (95.32% of the total emissions). The results demonstrate that the better fuel alternative to use for yard tractors is hydrogen, which has the greatest effect on GHG mitigation, followed by electric and LNG. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Life cycle assessment Carbon footprint Green port LNG Hydrogen
1. Introduction Based on the statistics released by the World Bank (2018) [1], global GDP has shown a positive growth between 2005 and 2017, except for the years of 2008 and 2009 in which a financial tsunami broke out, and growth is predicted to recover in 2017e2019. In addition, the International Monetary Fund (IMF, 2018) [2]estimated the growth rates of 2017 and 2018 in global economy could reach to around 3.7%, and Taiwan would see an increase of around 2.9% and 2.7%, respectively. Generally, international trade is one of the engines derived from global economic growth. The main forms of freight for international trade involve ocean shipment, air transport, and railroad transport. According to the Review of Maritime Transport released by the United Nations Conference on Trade and Development (UNCTAD) in 2017, goods transported internationally by sea accounted for about 80% of overall trade volume in 2016, an increase of 2.6% over 2015. A 3.2% annual rise is also predicted from 2017 to 2022, indicating that
* Corresponding author. E-mail addresses: [email protected] (C.-C. Chang), pchuang99tw@gmail. com (P.-C. Huang), [email protected] (J.-S. Tu). https://doi.org/10.1016/j.energy.2019.116222 0360-5442/© 2019 Elsevier Ltd. All rights reserved.
the development of the global economy highly relies on maritime transport and that the growth would continue year after year in the future. The International Monetary Fund (2018) [2] and Review of Maritime Transport released by the UNCTAD (2018) [3] reported global GDP is expected to grow by more than 3.0% and 3.8% over the 2018e2023 period, respectively. The Review of Maritime Transport released by the UNCTAD (2017) [4] indicated that container trade went up 14.94% from 1980 to 2016. The volume of maritime trade surged as a result of busing operations at sea ports. Nowadays, most of the container-handling and transport equipment at port still uses diesel for fuel. During operation, (especially yard tractors) they release large volumes of greenhouse gases and toxic substances, especially diesel particulate matter (DPM). The California Air Resources Board (CARB) has pointed out that the exhaust discharged from the use of diesel for fuel contains toxic substances, among which DPM is the main pollutant. According to data from CARB, the toxic air pollutant can increase cancer risk by 70%, and it is probably a principal cause of lung cancer, including lung adenocarcinoma. The Environmental Protection Agency’s (EPA, 2009) [5] Current Methodologies in Preparing Mobile Source Port-Related Emissions Inventories indicates that the main sources of greenhouse gases in
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harbor areas include commercial vessels, harbor vessels, container handling equipment, locomotives in harbor areas, and motor vehicles going in and out of harbors. These five sources could have a rather large environmental impact on harbors and the surrounding areas. In response, all major ports around the world have started to establish concrete measures to reduce emissions from the above mentioned sources of pollution. The most famous is the San Pedro Bay Port Clean Air Action Plan, which was announced in 2006 to set emissions standards at the two largest ports, the Port of Los Angeles and the Port of Long Beach. It was suggested in the San Pedro Bay Ports Clean Air Action Plan that the machine equipment applied in harbor areas could use alternative fuels or fuels with higher efficiency, or the engines of such equipment could be changed in order to reduce the amounts of toxic exhaust emitted. The annual report of the Port of Long Beach and the Port of Los Angeles presented the Technology Advancement System (TAP) in 2013 and proposed to use new shortdistance trucks and tractors running on batteries or hydrogen fuel cells to achieve the goal of green ports. Previous literature has applied life cycle assessment and carbon footprint to study the power sources of transportation and which method could save more energy and further reduce carbon emissions. (Zhang et al., 2017 [6]; Chang et al., 2016 [7]; Hwang, 2013 [8]; Arteconi et al. (2010) [9]). The findings of the study indicated that the use of hydrogen, energy could lower carbon emissions effectively (Bicer and Dincer, 2018 [10]; Castellani et al., 2018 [11]; Chang et al., 2016 [7]; Pereira et al., 2014 [12]; Wang et al., 2013 [13]; Arteconi et al., 2010 [9]). According to the statistics from Taiwan International Ports Corporation Ltd., (2017) [14] the tonnage of container handled in Taiwan in 2016 totaled 733,560,000 metric tons, indicating a 21.10% growth from 2009 to 2016. In the meantime, the container traffic in 2016 amounted to 531,287,000 shipping tons, making up the largest portion (72.43%) of the entire tonnage of container handled, and one important aspect in container handling is the use of yard tractors (truck tractors) to transport containers to and from the dock. Most of yard tractors in the world transport containers to and from the dock use diesel for fuel. They travel at low speeds and often remain idling while waiting for long periods of time on the dock. As a result, they emit considerable amounts of greenhouse gases and air pollutants which can cause cancer. Literature regarding the greenhouse gas emissions polluted by the yard tractors at port, pointed out that yard tractors were one of the main sources of carbon emissions on container docks and the carbon emissions from such vehicles were closely associated with importation/exportation (Yu et al., 2017 [15]; Villalba and Gemechu, 2011 [16]). And Villalba and Gemechu (2011) [16] further indicated that natural gas combustion was the biggest inland emissions source, which was followed by diesel and electric, respectively. They suggest that port authorities ought to improve their dock management to reduce carbon emissions. For this reason, this paper intends to analyze the use of alternative fuels to reduce emissions of toxic gases in harbor areas. The Port of Kaohsiung is an example to study this kind of issue. This should be a benchmark for ports managers in the world. Life cycle assessment and carbon footprint analysis are adopted to study the total exhaust emissions from yard tractors running on diesel and the ones using alternative fuels, and the carbon footprint difference between them, as well as to analyze the emissions hotspot of different types of fuel. Four ISO standards, namely ISO 14040:2006 [17] Environmental Management – Life Cycle Assessment – Principles and Framework; ISO 14044:2006 [18] Environmental Management – Life Cycle Assessment – Requirements and Guidelines; ISO 14064e1:2006 [19] Greenhouse gases – Part 1:
Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals; and ISO/TS 14067:2013 [20] Greenhouse gases – Carbon footprint of products – Requirements and guidelines for quantification and communication are applied to evaluate the carbon footprint throughout the life cycle of different fuels from cradle to grave. Tonkilometer is adopted as the functional unit. (The primary data are acquired from related businesses, and the secondary data come through SimaPro 8.0.) With all the above-mentioned combined, the objectives of this study include the following: (1) To examine the total emissions and carbon footprint of yard tractors using diesel and those using alternative fuels (electric, liquefied national gas, and hydrogen fuel cells) during the life cycle and to analyze the carbon footprint using tonkilometer as the functional unit (2) To establish the differences in emissions of greenhouse gases from the use of dissimilar fuels and emissions hotspot through carbon footprint comparison and analysis and to provide the results to related units for reference This paper is divided into five chapters. The first three chapters are the introduction, literature review and study methods, respectively. Chapter IV describes the process and outcome of the empirical analysis, and the conclusions and suggestions are in Chapter V. 2. Research methods This study analyses the carbon footprint of yard tractors at the Port of Kaohsiung. Consequently, we first interpret relevant ISO standards; then we explain the data source and the scope definition, followed by designing the process diagrams for four kinds of yard tractors; and finally we determine the variables and constructs definitions, and then the quantitative models are used to evaluate carbon footprint. 2.1. ISO standards 2.1.1. ISO 14040:2006 environmental management, life cycle assessment, principles, and framework The elements specified in ISO 14040:2006 [17] for the production system are depicted in Fig. 1. In this product system, one should describe the system boundaries to verify to what extend one needs to study. To be specific, the basic framework of life cycle assessment in this study contains the steps from the extraction of raw materials, the manufacturing, the final product, the usage, and finally the recycling, reusage or disposals. All these steps can be linked up by the transportation and utility input. For the usage scenario, this study focuses on the yard tractors that served for one-year trucking.
System Boundary
Utility Input
Recycle and Reuse Materials
Manufactuing
Products
Use Disposals
Transportations
Fig. 1. The system boundary.
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During this period, the element inputs will be the fuels, the clean water, and the maintenance. 2.1.2. ISO 14044:2006 environmental management, life cycle assessment, requirements, and guidelines This study also applied the standard of ISO14044:2006 [18], which describes the name and the function of the product system, the functional unit, the system boundary, the sequence of allocation, the relevant assumptions, the quality of the activity data, the methods and categories of the life cycle impact assessment, the research restrictions, and lastly the results. 2.1.3. ISO 14064e1:2006 greenhouse gases – part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals ISO 14064e1:2006 [19] identified the scope of what is important when calculating greenhouse gas emissions at the organizational level. The scopes are as follows, and those of Scope I and Scope II are covered. (1) Scope I emissions: Identify the direct emissions which are from factories owned by the respective organizations, which include coal combustion from burning boilers, power generators, gas, and air conditioners. (2) Scope II emissions: Identify the indirect emissions which are from electric, heat, and vapors that are purchased from outside. (3) Scope III emissions: These are the other emissions that are neither in Scope I nor in Scope II. For example, the emissions that came from employees’ commuting or the emissions produced by other organizations.
2.1.4. ISO/TS 14067: 2013 greenhouse gases d carbon footprint of products d requirements and guidelines for quantification and communication ISO/TS 14067:2013 [20] inherited the specifications of ISO 14040:2006 [17] and ISO 14044:2006 [18]. Correspondingly, ISO/TS 14067:2013 [20] emphasized that the contributions of carbon dioxide are equivalent to the global warming potential instead of describing the contributions of other impacts or discussing the problems based the social level or economic level. There are two types of carbon footprints under the standard of ISO 14064e1:2006 [19] and ISO/TS 14067:2013 [20]. The differences between these two types are listed in Table 1 below: 2.2. The scope of operations and research data The carbon footprint evaluation aims at a forwarder which ran the trucking business with 40-foot container at the Port of Kaohsiung. This paper collected activity data based on the process diagram since this research is using the approach of the activity data multiplied by GHG emissions or removal factors to evaluate the
3
carbon footprint, in this paper the impact assessment refers to the global warming potential (GWP100) from the IPCC (2013) [21]. In addition, we refer to the GHG emissions factors from the Simapro 8.0 database and the Carbon Footprint Calculation Platform set up by the Environmental Protection Administration of Taiwan. The functional unit was represented by ton-kilometers. The system was from cradle to grave, which contained the utility and the maintenance from the extraction of the raw materials, the manufacturing, and the trucking service to the disposal of the yard tractors in 2015. The trash produced by the yard tractor drivers was included as well. This study excluded several emissions sources from the trucking service: including capital goods such as the office building, the parking lot, the maintenance plant, the infrastructure of the port, the gas station, the charging station, the LNG filling station, and the body of the yard tractor. And, the calculation also omitted the emissions from the administration staff. 2.3. The process diagram of the yard tractors This paper was designed the process diagrams of four different yard tractors. As illustrated in these diagrams, the utility contains the fuels, the clean water, and the refrigerant; while, the maintenance was narrowed down to regular maintenance and unexpected maintenance. The disposals were referred to the manual of the Example Industrial Waste Disposal Plan for Land transportation, Water transportation and Support Activities for Transportation published by the Environment Protection Administration (2013) [22]. We then illustrate the process diagrams in detail in the following sections. 2.3.1. The process diagram of the diesel yard tractors The inventory of the diesel yard tractor was achieved as follows. First, the secondary data of the extraction of raw materials and manufacturing can be narrowed down to the utility input and the maintenance suppliers. Maintenance can be divided into regular maintenance and unexpected maintenance. Second, the container trucking contains the diesel fuel consumptions and refrigerant. Generally, the forwarder provides primary data, such as the consumption volume of fuel and the maintenance schedule, and its item list during trucking. Third, the disposals cover the energy consumption and maintenance when recycling and disposing of waste. All these things are illustrated in Fig. 2 below. 2.3.2. The process diagram of the electric yard tractors The inventory of the electric yard tractor was obtained as follows. First, the extraction of raw materials and manufacturing can be narrowed down to the utility input and maintenance supplies. We referred to the maintenance schedule on the Leaf service and maintenance guide released by the Nissan Motor Corporation (2012) [23]. Second, container trucking contains the electric consumption and refrigerant. Third, disposals cover energy consumption and maintenance when recycling and disposing of waste. All these things are shown in Fig. 3.
Table 1 Comparisons between two types of carbon footprints. Greenhouse gases at the organizational level To quantify Scope I emissions and Scope II emissions only To cover emissions of the six main greenhouse gases: CO2, CH4, N2O, PFCS, HFCS, and SF6
Carbon footprint of products
To quantify all three scope emissions To include six main greenhouse gases and the controlled substance listed in the Montreal Protocol Except for the CO2 from the combustion of the biomass/biofuels To cover all the greenhouse gases from the combustion of the fossil fuels and biomass/biofuels The electric generated at the target organization and then sold to other factories is counted as The electric generated at the target organization and then sold to other one of the scope I emissions factories should be excluded
4
C.-C. Chang et al. / Energy 189 (2019) 116222
The Process Diagram of The Diesel Yard Tractor Extraction of raw materials and Manufacturing
Use (Trucking)
Disposals
Maintenance supplies Regular maintenance Clean water, Grease, Engine oil, Oil filter, Air filter, Gear core, Brake fluid, Gear oil Unexpected maintenance Tank, Quartz bulb, Turn signal flasher, Fence, Front supporting frame, Clutch operating cylinder, ip6m/m quick coupling, Former car fenders, Air suspension bags, Automatic circuit breaker, Dual wick lamp, JOST wooden disc springs, Muffler holder, Muffler beam Utility Input Material flow Energy flow Maintenance
Diesel refining Refrigerant Water purification
Gas station Dealer Water plant
Cargo trucking
Maintenance plants In the shop Incineration plant
Inspection Repairs
Disposal
Washing
Waste water
Landfill Recycling plant
Leave
Fig. 2. The process diagram of the diesel yard tractor.
The Process Diagram of The Electric Yard Tractor Extraction of raw materials and Manufacturing
Use (Trucking)
Disposals
Maintenance supplies Regular maintenance Clean water, Grease, Gear core, Brake fluid, Gear oil
Cargo trucking Maintenance plants In the shop
Incineration plant
Inspection Utility Input Material flow Energy flow Maintenance
Electricity generating
Power station
Refrigerant
Dealer Water plant
Water purification
Repairs
Disposal
Washing
Waste water
Leave
Landfill Recycling plant
Fig. 3. The process diagram of the electric yard tractor.
depicted in Fig. 5 below.
2.3.3. The process diagram of the LNG yard tractors The inventory of the LNG yard tractor contains the following. First, the extraction of raw materials and manufacturing can be narrowed down to the utility input and maintenance supplies. We referred to the maintenance information of the manual of engines maintenance provided by Cummins Westport Incorporation (2015) [24]. Second, container trucking contains the LNG consumptions and refrigerant. Third, disposals cover energy consumption and maintenance when recycling and disposing of waste. All these items are illustrated in Fig. 4 below.
2.4. The variables definition and the model construction
2.3.4. The process diagram of the hydrogen yard tractors The inventory of the hydrogen yard tractor is described as follows. First of all, the extraction of raw materials and manufacturing can be narrowed down to the utility input and maintenance supplies. We estimated the maintenance information based on the suggested maintenance schedule of the Tucson provided by Hyundai Motor Corporation (2010) [25]. Second, container trucking contains the liquefied hydrogen consumptions and the refrigerant. Third, disposals cover the energy consumption and maintenance when recycling and disposing of waste. All these things are
2.4.1. Variables definition The basic concept for this calculating model is the tons of the container multiplied by the container volume, then multiplied by the transportation distance to get the total carbon emissions. For further discussion, we have listed several assumptions here, in which the tons of a container weigh the maximum weight of a 40foot container carrier, the container volume was approximately estimated to be 16,000 in 2015, and the transportation distance was presented by the average transport distance of a forwarder at port number 43 in 2015. Therefore, the inventory results can be revealed by the total carbon emissions or by the per ton-kilometers carbon
2.3.5. Fuel efficiency and emission factors of yard tractors The fuel efficiency and emission factor of the different types of yard tractors, including diesel yard tractors, electric yard tractors, LNG yard tractors and hydrogen yard tractors used in this study are presented in Table 2.
C.-C. Chang et al. / Energy 189 (2019) 116222
5
The Process Diagram of The LNG Yard Tractor Extraction of raw materials and Manufacturing
Use (Trucking)
Disposals
Maintenance supplies Regular maintenance Clean water, Grease, Gear core, Brake fluid, Gear oil, Natural gas engine oils, Natural gas filters, Sparkplug
Cargo trucking Maintenance plants In the shop
Gas liquification Refrigerant
Material flow Energy flow Maintenance
Water purification
Incineration plant
Inspection
Utility Input
Repairs
Disposal
Washing
Waste water
Filing station
Dealer Water plant
Landfill Recycling plant
Leave
Fig. 4. The process diagram of the LNG yard tractor.
The Process Diagram of The Hydrogen Yard Tractor Extraction of raw materials and Manufacturing
Use (Trucking)
Disposals
Maintenance supplies Regular maintenance Clean water, Grease, Engine oil, Oil filter, Air filter, Gear core, Brake fluid, Gear oil, Coolant core
Cargo trucking Maintenance plants In the shop
Utility Input Hydrogen generating
Material flow
Refrigerant
Energy flow Maintenance
Water purification
Incineration plant
Inspection
Gas station Dealer Water plant
Repairs
Disposal
Washing
Waste water
Leave
Landfill Recycling plant
Fig. 5. The process diagram of the hydrogen yard tractor.
Table 2 Comparisons between two types of carbon footprints.
Fuel Efficiency Emission Factor e Extraction Emission Factor e Usage
diesel yard tractors
electric yard tractors
LNG yard tractors
hydrogen yard tractors
2.43 km/L 0.760 2.730
11.54 kW h/hr 0.69 e
0.9125 km/L 0.343 2.234
16 km/kg 6.970 e
footprint. The variables and their definitions are presented in Table 3.
TKiloi ¼ TD CP CQ CFPi ¼
2.4.2. Model construction of carbon footprint Based on the standardized carbon footprint indicators, the carbon footprint calculating model is exhibited as the following equations (1)e(4):
TCEMi TKiloi
(3) (4)
3. Empirical analysis
TCEMi ¼
4 X 32 X 6 X
ACijk LCEFjkl GWPjkl
(1)
3.1. The carbon footprint of the diesel yard tractor
(2)
The total greenhouse gas emissions and the carbon footprint of the diesel yard tractor are recorded in Table 4 below. First, the total greenhouse gas emissions of the diesel yard tractor is 43,870.60 kgCO2e. The first three emissions sources were the diesel
j¼1 k¼1 l¼1
LCEFjkl ¼ AMEFjkl þ TUEFjkl þ WEFjkl
6
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Table 3 Variables for the carbon footprint of the yard tractors. Variables Definitions ACijk AMEFjkl TUEFjkl WEFjkl LCEFjkl GWPjkl TKiloi TD CP CQ TCEMi CFPi i
j k
l
The activity data The yard tractor i uses fuel j, and replaces the maintenance k. Extraction and manufacturing emissions factors The extraction of the fuel j, and the manufacture of the maintenance k, the emittance of the greenhouse l. The emissions factor of the yard tractor in the usage stage The consumption of the fuel j, and the replacement of the maintenance k, the emittance of the greenhouse l. The emissions factor of the disposals The disposal treatment of the fuel j, and the disposal treatment of the maintenance k, the emittance of the greenhouse l. The emissions factor of the life cycle The consumption of the fuel j, and the replacement of the maintenance k, the emittance of the greenhouse l. The global warming potential The global warming potential of the greenhouse gas l of the consumption of the fuel j, and the replacement of the maintenance k in the life cycle. Ton-kilometers The sum of the weight of a unit container multiplied by the transportation distance The transportation distance The average transportation distance of the yard tractor to transport a 40-foot container. Carrying capacity The maximum weight a 40-foot container can be carried The container quantity The container quantity that a forwarder deals with in 2015 The total carbon emissions throughout the life cycle The total carbon emissions of the yard tractor i. The carbon footprint The carbon footprint of the yard tractor i presented in ton-kilometers. i represents the categories of the yard tractors, i ¼ 1; 2; 3; 4. In which, i ¼ 1 represents the diesel yard tractor; i ¼ 2 represents the electric yard tractor; i ¼ 3 represents the LNG yard tractor; i ¼ 4 represents the hydrogen yard tractor. j represents the categories of the fuels, j ¼ 1; 2; 3; 4. In which, j ¼ 1 represents the diesel fuel; j ¼ 2 represents the electric power; j ¼ 3 represents the LNG; i ¼ 4 represents the liquefied hydrogen. k represents the items of the maintenance, k ¼ 1; 2; /; 32. In which, k ¼ 1 represents the grease; k ¼ 2 represents the gear core; k ¼ 3 represents the brake fluid; k ¼ 4 represents the gear oil; k ¼ 5 represents the air filter, /, k ¼ 31 represents the climate control air filter; and k ¼ 32 represents the core coolant. l represents the categories of the greenhouse gases, l ¼ 1; 2; /; 6. In which, l ¼ 1 represents the carbon dioxide (CO2); l ¼ 2 represents the methane (CH4), l ¼ 3 represents the nitrous oxide (N2O), l ¼ 4 represents the perfluorocarbons (PFCS), l ¼ 5 represents the chlorofluorocarbons (HFCS), and l ¼ 6 represents sulfur hexafluoride (SF6)
Table 4 The carbon footprint of the diesel yard tractor. Stages The raw materials and manufacturing of yard tractor The use of yard tractors (trucking)
Diesel refining Maintenance supplies Diesel Refrigerant
The disposals of yard tractors Life cycle carbon footprint (total carbon emissions) Carbon footprint per ton kilometers (kgCO2e/TK)
consumption in the usage stage of 33,703.70 kgCO2e (76.83%), the diesel refining of 9382.72 kgCO2e (21.39%), and the refrigerant in the usage stage of 372.80 kgCO2e (0.85%). In short, the diesel consumption in the usage stage (trucking service) is the highest emissions hotspot throughout the whole life cycle. Second, the carbon footprint per ton kilometers is 6.40 106 kgCO2e/TK.
3.2. The carbon footprints of the alternative fuel yard tractors 3.2.1. The carbon footprint of the electric yard tractor The total greenhouse gas emissions and the carbon footprint of the electric yard tractor are listed in Table 5 below. First, the total greenhouse gas emissions of the electric yard tractor is 16,563.63 kgCO2e. The first three emissions sources were the electric generating of 15,925.20 kgCO2e (96.15%), the refrigerant leakage in the usage stage of 372.80 kgCO2e (2.25%), and the disposals of 235.4865 kgCO2e (1.42%). Moreover, the electric in the usage stage does not generate any greenhouse gas emissions, which leads to a carbon
Carbon Footprint
Percentage (%)
9382.72 173.76 33,703.70 372.80 237.62 43,870.60 6.40 106
21.39 0.39 76.83 0.85 0.54 100.00
footprint of 0. Second, the carbon footprint per ton kilometers is 2.42 106 kgCO2e/TK. 3.2.2. The carbon footprint of the LNG yard tractor The total greenhouse gas emissions and the carbon footprint of the LNG yard tractor are shown in Table 6 below. First, the total greenhouse gas emissions of the LNG yard tractor is 33,560.09 kgCO2e. The first three emissions sources were the LNG consumption in the usage stage of 28,538.85 kgCO2e (85.04%), the LNG refining of 4381.06 kgCO2e (13.05%), and the refrigerant in the usage stage of 372.80 kgCO2e (1.11%). If we compare these results with the diesel ones, we will find out that the first three emissions sources were the same. Second, the carbon footprint per ton kilometers is 4:89 106 kgCO2e/TK. 3.2.3. The carbon footprint of the hydrogen yard tractor The total greenhouse gas emissions and the carbon footprint of the hydrogen yard tractor are revealed in Table 7. First, the total
C.-C. Chang et al. / Energy 189 (2019) 116222
7
Table 5 The carbon footprint of the electric yard tractor. Stages The raw materials and manufacturing of yard tractor The use of yard tractors (trucking)
Carbon Footprint
Percentage (%)
Electric generating Maintenance supplies Electric Refrigerant
15,925.20 30.14 0.00 372.80 237.62 16,563.63 2.42 106
96.15 0.18 0.00 2.25 1.42 100.00
Carbon Footprint
Percentage (%)
NG liquefying Maintenance supplies LNG Refrigerant
4381.06 31.65 28,538.85 372.80 235.73 33,560.09
13.05 0.09 85.04 1.11 0.70 100.00
The disposal of yard tractors Life cycle carbon footprint (total carbon emissions) Carbon footprint per ton kilometers (kgCO2e/TK)
Table 6 The carbon footprint of the LNG yard tractor. Stages The raw materials and manufacturing of yard tractor The use of yard tractors (trucking) The disposal of yard tractors Life cycle carbon footprint (total carbon emissions) Carbon footprint per ton kilometers (kgCO2e/TK)
4:89 106
Table 7 The carbon footprint of the hydrogen yard tractor. Stages The raw materials and manufacturing of yard tractor The use of yard tractors (trucking)
Hydrogen liquefying Maintenance supplies Liquid hydrogen Refrigerant
The disposal of yard tractors Life cycle carbon footprint (total carbon emissions) Carbon footprint per ton kilometers (kgCO2e/TK)
greenhouse gas emissions of the hydrogen yard tractor is 13,709.87 kgCO2e. The first three emissions sources were the hydrogen liquefying of 13,068.75 kgCO2e (95.32%), the refrigerant leakage in the usage stage of 372.80 kgCO2e (2.72%), and the disposals of 235.89 kgCO2e (1.72%). Here we have adopted the analytical results of Hwang (2013) [8] and assumed that the hydrogen was from the methane reformation, which indicates that the greenhouse gas emissions of liquefied hydrogen in the usage stage is 0. From the above-mentioned analytical results, one will find out that the largest emissions source for the hydrogen yard tractor is hydrogen liquefying, which is similar to the electric yard tractor. Second, the carbon footprint per ton kilometers is 2.00 106 . 3.3. The benefits analysis of carbon footprint mitigation using alternative fuel yard tractors The histogram of the emissions normalizations of these four kinds of yard tractors is illustrated in Fig. 6 below. According to this histogram, both LNG and diesel consumption in the trucking stage are the largest hotspots for the LNG and diesel yard tractors, which accounts for 85.04% and 76.83%; the material fuel is the largest emissions source for both the electric yard tractor and the hydrogen yard tractor, which accounts for 96.15% and 95.32%, respectively If we address the carbon footprint using per ton-kilometers, we comprehend that all three types of alternative yard tractors have the benefit of greenhouse gas eliminations. These eliminations, listed from the highest to the lowest, are the hydrogen yard tractor of 4.40 106 kgCO2e (or 68.75%), the electric yard tractor of 3.98 106 kgCO2e (or 62.24%), and the LNG yard tractor of 1.51 106 kgCO2e (or 23.59%), all of which are shown in Table 8.
Carbon Footprint
Percentage (%)
13,068.75 32.43 0.00 372.80 235.89 13,709.87 2.00 106
95.32 0.24 0.00 2.72 1.72 100.00
3.4. Policy suggestions Based on the above-mentioned results, this paper proposes several policies, which are stated as follows. First, the diesel yard tractor should be equipped with carbon-reducing technology and the engine turned off when lying idle. The administration should advocate and promote eco-driving for both, thus eliminating the fuel combustion emissions in the stage of container trucking. Second, the authorities should introduce more efficient methods of energy-generating for the electric yard tractor and the hydrogen yard tractor to lessen greenhouse gas emissions. Third, the government should fund a more environmentally-friendly refrigerant
100% 90% 80% 70% 60% 50% 40% 30%
Disposal
20%
Trucking-maintenance
10% 0%
Trucking-fuel Material-maintenance
Diesel
Electric
LNG
Hydrogen
Material-fuel
Fig. 6. The percentage of life cycle emission of the yard tractors.
8
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Table 8 The comparison of the carbon footprint in each stage of life cycle. Stages Material and Manufacturing Use (trucking)
Fuels Maintenance supplies Energy Refrigerant
Disposals Carbon footprint per ton - kilometers (kgCO2e/TK)
Diesel (baseline)
Electric (difference)
LNG (difference)
Hydrogen (difference)
9382.72 173.76 33,703.70 372.80 237.62 6.40 106
þ6542.48 (þ69.73%) 143.62 (82.65%) 33,703.70 (100.00%) 0.00 (0.00%) 2.13 (0.90%) 3.98 106 (-62.24%)
5001.66 (53.31%) 142.11 (81.78%) 5164.85 (15.32%) 0.00 (0.00%) 1.89 (0.79%) 1.51 106 (-23.59%)
þ3686.03 (þ39.29%) 141.33 (81.34%) 33,703.70 (100.00%) 0.00 (0.00%) 1.72 (0.73%) 4.40 106 (-68.75%)
to substitute the moderate refrigerant for reducing the carbon emissions of the LNG yard tractor. 4. Conclusions and suggestions This paper conducted the life cycle assessment mentioned in several ISO standards to evaluate the carbon footprints of the yard tractors at the Port of Kaohsiung that use different fuels as power sources. The scopes are evaluated from cradle to grave and the functional units are based on per ton-kilometer. The main findings of this study are as follows: (1) For the diesel yard tractor, the total carbo 106 n emissions is 43,870.60 kgCO2e, and the carbon footprint is 6.40 106 kgCO2e/TK. In addition, the largest emissions hotspot is the fuel in the usage stage, which produces 33,703.70 kgCO2e that accounts for 76.83% of total emissions. (2) For the electric yard tractor, the total carbon emissions is 16,563.63 kgCO2e, and the carbon footprint is 2.42 106 kgCO2e/TK. Also, the major emissions hotspot is the fuel in the raw material stage, which generates 15,925.20 kgCO2e that accounts for 96.15% of total emissions. (3) For the LNG yard tractor, the total carbon emissions is 33,560.09 kgCO2e, and the carbon footprint is 4.89 106 kgCO2e/TK. Moreover, the main emissions hotspot is the fuel in the usage stage, which creates 28,538.85 kgCO2e that accounts for 85.04% of total emissions. (4) For the hydrogen yard tractor, the total carbon emissions is 13,709.87 kgCO2e, and the carbon footprint is 2.00 kgCO2e/ TK. Furthermore, the biggest emissions hotspot is the hydrogen liquefying, in the raw material stage, which yields 13,068.75 kgCO2e that accounts for 95.32% of the total emissions. After comparing the alternative fuel yard tractors with the traditional diesel one, the results have illustrated that all three types of alternative fuel yard tractors have the benefit of greenhouse gas mitigation. The greenhouse gas reductions of the electric yard tractor and LNG yard tractor are 62.24% and 23.59% less than the diesel yard tractor. However, the hydrogen yard tractor has the largest greenhouse gas reduction, which is 68.75% less than the emissions of the diesel yard tractor. Moreover, the usage stage of the hydrogen yard tractor is 100% less than that of the diesel yard tractor. According to the above-mentioned findings, this paper suggests that the diesel yard tractor at the Port of Kaohsiung should steadily be replaced by the hydrogen yard tractor which would help to achieve the goal of green harbor construction and economic development simultaneously. Acknowledgement The authors acknowledge the Ministry of Science and Technology, Taiwan, ROC for providing partial funding to support under contract numbers MOST 107-2410-H-006-076.
References [1] World Bank. Global economic prospects: divergences and risks. Retrieved from, https://openknowledge.worldbank.org/handle/10986/29801; 2018. [2] IMF. World economic outlook. Retrieved from, https://www.imf.org/external/ datamapper/NGDP_RPCH@WEO/OEMDC/ADVEC/WEOWORLD/IRQ; 2018. [3] Review of maritime transport. Retrieved from, https://unctad.org/en/ PublicationsLibrary/rmt2018_en.pdf; 2018. [4] Review of maritime transport. Retrieved from, https://unctad.org/en/ PublicationsLibrary/rmt2017_en.pdf; 2017. [5] Environment Protection Administration. Current methodologies in preparing mobile source port-related emission invenories. Retrieved from, https://www. epa.gov/sites/production/files/2016-06/documents/2009-port-inventoryguidance.pdf; 2009. [6] Zhang Y, Jiang H, Li J, Shao S, Hou H, Qi Y, Zhang S. Life cycle assessment and optimization analysis of different LNG usage scenarios. Int J Life Cycle Assess 2017:1e10. [7] Chang CC, Wu FL, Lai WH, Lai MP. A cost-benefit analysis of the carbon footprint with hydrogen scooters and electric scooters. J Hydrogen Energy 2016;41:13299e307. [8] Hwang JJ. Sustainability study of hydrogen pathways for fuel cell vehicle applications. Renew Sustain Energy Rev 2013;19:220e9. [9] Arteconi A, Brandoni C, Evangelista D, Polonara F. Life-cycle greenhouse gas analysis of LNG as a heavy vehicle fuel in Europe. Appl Energy 2010;87(6): 2005e13. [10] Bicer Y, Dincer I. Life cycle environmental impact assessments and comparisons of alternative fuels for clean vehicles. Resour Conserv Recycl 2018;132(1):141e57. [11] Castellani B, Rinaldi S, Bonamente E, Nicolini A, Rossi F, Cotana F. Carbon and energy footprint of the hydrate-based biogas upgrading process integrated with CO2 valorization. Sci Total Environ 2018;615:404e11. [12] Pereira SR, Fontes T, Coelho MC. Can hydrogen or natural gas be alternatives for aviation? A life cycle assessment. Int J Hydrogen Energy 2014;39(25): 13266e75. [13] Wang DW, Zamel N, Jiao K, Zhou YB, Yu SH, Du Q, Yin Y. Life cycle analysis of internal combustion engine, electric and fuel cell vehicles for China. Energy 2013;59:402e12. [14] Taiwan International Ports Corporation. Annual statistic report: 2015. Taiwan, ROC: Taiwan International Ports Corporation, Ltd.; 2017. Kaohsiung. [15] Yu H, Ge YE, Chen J, Luo L, Tan C, Liu D. CO2 emission evaluation of yard tractors during loading at container terminals. Transp Res D Transp Environ 2017;53:17e36. [16] Villalba G, Gemechu ED. Estimating GHG emissions of marine ports-the case of Barcelona. Energy Policy 2011;39(3):1363e8. [17] ISO 14040. Environmental management – Life cycle assessment – Principles and framework. 2006. [18] ISO 14044. Environmental management – Life cycle assessment – Requirements and guidelines. 2006. [19] ISO 14064-1. Greenhouse gases – Part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals. 2006. [20] ISO/TS 14067. Greenhouse gases d carbon footprint of products d Requirements and guidelines for quantification and communication. 2013. [21] IPCC. Climate change 2013: the physical science basis. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press; 2013. [22] Environmental Protection Administration. Carbon footprint calculation Platform. Retrieved from, https://cfp-calculate.tw/cfpc/WebPage/LoginPage.aspx; 2013. [23] Nissan Motor Corporation. 2013 Leaf service and maintenance guide. Retrieved from, https://owners.nissanusa.com/content/techpub/ ManualsAndGuides/NissanLEAF/2013/2013-NissanLEAF-service-maintenance-guide.pdf; 2012. 38. [24] Cummins Westport Incorporation. ISL G brochure, 6. Retrieved from, http:// www.cumminswestport.com/content/430/ISL%20G%204971499_0315.pdf; 2015. [25] Hyundai Motor Corporation. Hyundai Tucson: normal maintenance schedule. 2nd 2010 Retrieved from. http://www.htmanual.net/normal_maintenance_ schedule-409.html.