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In this study, the GHG emissions from marine vessels were estimated using the measureable port-related activities within the boundaries of Busan Port. Specifically, the port-related activities of the various types of marine vessels and their specifications were collected from the Port Management Information System (PORT-MIS), which tracks and records the movement of marine vessels entering and departing the port of Busan. Based on the estimation methods established by the National Institute of Environmental Research (2007), this study estimated the GHG emissions from marine vessels according to two types of ship operation: maneuvering (i.e., main engine emissions are dominant but at lower loads) and hotelling (i.e., the emissions from auxiliary engines dominate with the main engine off).

Eq. (1) represents the GHG emissions of marine vessels operating in maneuvering mode.

where md_i is the maneuvering distance of the ith vessel (km), fe_i is the fuel economy of the ith vessel (L/km) in gross tonnage, as shown in Table 1, n is the total number of vessels during the analysis period, and ef_p is the emission factor for pollutant p in which 1, 2, and 3 were coded for CO₂, N₂O, and CH₄, respectively (see Table 2). The maneuvering distance of each vessel was estimated by measuring the roundtrip distance between the berthing terminal and the boundary of Busan Port on the electronic navigational chart.

For estimating the GHG emissions in hotelling, Eq. (2) was used.

where fc_i is the fuel consumption of the ith vessel at full power (ton/day), the factor 0.2 is used to reflect that the hotelling fuel consumption is about 20% of the full power fuel consumption, the factor of 0.79 (day/vessel) is the average hotelling time of marine vessels in Korea, and the rest of the notations are as previously stated. Since any specific hotelling characteristics of the vessels whose arrival purposes were not directly related to freight and passenger loading and unloading were unknown, the hotelling GHG emissions were only estimated for the marine vessels whose arrival purpose was either freight/passenger loading or unloading.

The fuel consumption estimated as a function of gross tonnage, shown in Table 3, was used as a default value for each vessel. However, the hotelling GHG emissions of several vessels of unknown type (Table 3) were estimated using the fuel consumption factors for “All ships”, as recommended by the National Institute of Environmental Research (2007). Finally, the total GHG emissions of marine vessels arriving in and departing from Busan Port were estimated simply by summing the maneuvering and hotelling emissions.

The cargo handling equipment (CHE) inventoried in this study consisted of container cranes (CC), transfer cranes (TC), reach stackers (RS), and yard tractors (YT), all of which are used for loading and/or discharging cargo on terminals in the port of Busan. Since each piece of cargo handling equipment has a different energy consumption rate for dealing with 1-TEU, the energy consumption rate for each piece of equipment at a terminal in Busan Port was examined in 2008.

Table 4 represents the energy consumption rates for each CHE obtained from the one-year sample dataset on a container terminal in the port of Busan; these rates are very similar to those examined in the port of Gwangyang (Kim et al., 2007). Consequently, the GHG emissions of CHE were estimated using Eq. (3).

where ec_j is the energy consumption of the jth CHE in dealing with 1-TEU, CHE_tj is the number of the jth CHE operated in terminal t, TEU_t is the total TEUs on terminal t, and the rest of the notations are as previously stated. When estimating the GHG emissions from the CC and electric transfer crane (e-TC), the estimated electricity consumption rates of the equipment were converted to “TJ” using the annual national electricity productions (For more information about the conversion and emission factors, see Yang et al., 2010).

Unlike the marine vessels and CHE, the port-related activities of trucks have not been systematically maintained by BPA. Thus, the travel demand model was employed to estimate the truck activities represented as the vehicle kilometers traveled (VKT), as in a previous study (Starcrest Consulting Group, 2007). The estimation procedure for obtaining GHG emissions of heavy-duty trucks is illustrated in Fig. 1.

Fig. 1. 
Estimation procedure for heavy-duty trucks.

Specifically, the activities of trucks that traveled to the port of Busan were estimated using the Korea Transport Database (KTDB) disseminated by the Korea Transport Institute (2005). The KTDB consists of the number of trips between the specified 659 traffic analysis zones (TAZs) in the Busan metropolitan area and the associated roadway networks. To estimate the emissions from trucks that traveled to the port of Busan, the trip frequencies of trucks between TAZs containing terminals in the port of Busan were extracted using the guidelines provided by the Korea Development Institute (2008).

Using the manipulated truck trip frequencies and roadway network as the input dataset in the travel demand model, this study estimated the vehicle kilometers traveled (VKT) of the trucks within the analysis boundaries. The VKTs of the trucks can be reported as the output of the travel demand model. Due to the lack of truck activity data on terminals, this study exclusively analyzed the truck emissions using the onroad activities consisting of travel on public roadways outside the boundaries of Busan Port but within the boundaries of the Busan metropolis. Relevant references providing greater detail on the travel demand model are available (e.g., Ortuzar & Willumsen, 2001; Korea Development Institute, 2008).

The modeling results show that the trucks transporting cargo to and from the port of Busan generally travel via expressway. Specifically, more than 30% of the container truck trips travel on urban highways, such as Beonyeong Road and Dong-seo Road, connecting several terminals in the port of Busan and Expressway No. 1 and Expressway No. 10, respectively.

Table 5 shows a brief example of the travel demand model results containing the truck traffic volumes and speeds on the roadways in the boundary of Busan. Using this result, the VKT of the trucks for each roadway section (vehicle∙kilometers/day) can be easily calculated by multiplying the truck traffic volume by the roadway length. For example, the truck-VKT for link ID 1 can be estimated as 3,858 trucks∙kilometers/day (i.e., 2.5×1543).

To estimate the GHG emissions from the trucks transporting cargo to or from the port of Busan, Eq. (4) was used.

where TV_i is the truck volume assigned on the ith roadway segment (trucks/day), L_i is the length of the ith roadway segment within the boundary of Busan, and ef_p is the emission factor for pollutant p when the travel speed is about 50 kph. To take into account the uncertainty of the emission factor, the lower and upper emission factors were estimated using the emission factor function developed by the Motor Vehicle Emission Research Laboratory (2001). Specifically, the lower and upper emission factors were estimated using the travel speeds 40 kph and 50 kph, respectively (see Table 6).

To estimate the activity-based emissions of the railroad locomotives in the port of Busan, the total amount of TEUs transported by railroad locomotives arriving in and departing from the port of Busan from 2000 to 2007 were collected based on the data of the Korea Railroad Corporation. The statistics show that 3,046,670 TEUs were transported through 1,433,459 railroad cars from two railroad stations in the port of Busan (Busanjin and Sinseondae) to 34 other stations during the analysis period.

The emissions from railroad locomotives were estimated based on the on-railroad activities within the metropolitan boundaries of Busan using Eq. (5).

where CKT_i is the car kilometers traveled (car-100 km) from the ith station in the port of Busan, fe_CKT is the fuel economy (L/car-100 km), as summarized in Table 7, and ef_p is the emission factor (see Table 8).

To obtain the CKT activities, the total number of cars in each train arriving in and departing from Busanjin and Sinseondae stations in the port of Busan were multiplied by the travel distance within the boundaries of Busan from the two stations to the other 34 stations, distances which ranged from 22 km to 53 km.