## 3 Result and Discussion
### Optimizing the Vessel's Operation Condition  
According to [PERSON] et al. (2005), container ships sailing in the European-Far East sail approximately 23,692 miles one way and approximately 13,662 miles in the Far East-North America [39]. Most of the sailing sections of ships engaged in international trade operate their engine at a high rpm range, and when considering the operating time for \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**SSD 1**} & \multicolumn{2}{c}{**SSD 2**} & \multicolumn{2}{c}{**HSD 1**} & \multicolumn{2}{c}{**HSD 2**} & \multicolumn{2}{c}{**HSD 3**} \\ \cline{2-10}  & **C** & **M** & **C** & **M** & **C** & **C** & **M** & **C** & **M** & **C** \\ \hline Q1 & 3156.83 & 3148.50 & 3131.81 & 3132.07 & 3111.34 & 3154.53 & 3144.60 & 3147.08 & 3150.46 & 3158.67 \\ Q3 & 3162.93 & 3151.04 & 3138.43 & 3136.94 & 3148.55 & 3158.86 & 3156.50 & 3157.73 & 3164.37 & 3162.12 \\ Median & 3160.36 & 3149.84 & 3135.56 & 3135.16 & 3139.24 & 3157.33 & 3150.45 & 3155.11 & 3159.73 & 3160.53 \\ Average & 3156.82 & 3149.86 & 3132.36 & 3134.44 & 3128.31 & 3155.55 & 3146.41 & 3147.34 & 3156.30 & 3159.85 \\ Stand. DV & 27.61 & 2.03 & 28.89 & 3.75 & 25.09 & 5.01 & 16.37 & 18.91 & 11.20 & 3.42 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Fuel-based CO\({}_{2}\) emission analysis results of this study (unit: kg/tonne-fuel). \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**This Study**} & \multicolumn{2}{c}{**EEA [37]**} & \multicolumn{2}{c}{**IMO [36]**} & \multicolumn{2}{c}{**[PERSON] [31]**} & \multicolumn{2}{c}{**[PERSON] et al. [38]**} \\ \cline{2-10}  & **SSD** & **HSD** & **LFO** & **MGO** & **LFO** & **MGO** & **HH** & **DFH** & **XYH** & **Compercial** \\ \hline Emission factor & 3144.32 & 3150.58 & 3151 & 3206 & 3114 & 3206 & 3071 & 3153 & 3151 & 3170 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison with other studies and criteria (unit: kg/tonne-fuel). one round trip, CO\({}_{2}\) emissions in the seas are known to be high in absolute volume terms when compared with sections close to land. i.e., to minimize CO\({}_{2}\) emissions due to the international shipping trade, it is more effective to intensively manage CO\({}_{2}\) emissions in the ocean rather than emissions in areas close to land. [PERSON] et al. (2020) demonstrated that CO\({}_{2}\) emissions from a ship's main propulsion can be reduced by controlling the speed of ships through the energy efficiency design index (EEDI) [40]; many studies have thus suggested that CO\({}_{2}\) emissions may be significantly reduced by applying the EEDI to Very Large Crude Carrier and cargo ships [41; 42]. It is expected that CO\({}_{2}\) emissions from ships can be minimized by further expanding the widely implemented EEDI and modifying the energy efficiency existing ship index (EEXI). Currently, systems such as the EEDI, EEXI, and ship energy efficiency management plan (SEEMP) are being implemented to minimize CO\({}_{2}\) emissions by maximizing energy efficiency. However, some experts suggest that these are not effective [43; 44]. However, as shown in Figures 6 and 7, there is a difference in CO\({}_{2}\) emissions depending on the rpm range. So, this study analyzed the correlation between a vessel's speed and CO\({}_{2}\) emissions to derive the optimal operating speed. A simulation was conducted by setting up a virtual route between the Far East (Ulsan, Republic of Korea) and the Middle East (Ras Tanura, Saudi Arabia), which is mainly used to transport crude oil, as shown in Figure 11. The sailing distance is approximately 6382 miles one way, and the rpm, speed, fuel consumption, and speed-specific fuel-based CO\({}_{2}\) emission factor of the five test vessels were set as determining factors. As shown in Figure 12, the rpm is divided into six levels, and the total CO\({}_{2}\) emissions are calculated considering the average speed, navigation period, and fuel consumption for each section.