3.1.2. MGO Supply Chain

South Korea imported approximately 3 million b/d (barrels per day) of crude oil and condensate charting the fifth largest importer in global market. More than 82% of crude oil import was from Middle East [37]. Given this, MGO import from Saudi Arabia to South Korea is assigned to be Case 3. In addition, MGO distribution from U.S. to South Korea is chosen as Case 4 for consistency with the LNG supply point of U.S.

#### 3.1.3. Product System and Functional Unit

WtT analysis represents all steps from fuel extraction to storage in onboard tank. TtW analysis includes actual fuel combustion for ship propulsion. WtT and TtW analyses are integrated to provide a total WtW analysis. Functional unit is defined to be the supply and the consumption of 1.0 <sup>×</sup> 107 MJ LHV of fuels in consideration of the fuel tanks of a case study vessel which is equipped with 500 m<sup>3</sup> of LNG tank and 400 m3 of MGO tank. Taking into account the density of LNG, 450 kg/m3, 225 tons of LNG is fueled at fully fueled tank [38]. With 48.9 MJ/kg of LHV, LNG fuel provides 1.1 <sup>×</sup> 107 MJ of energy. 1.0 <sup>×</sup> 107 MJ LHV of energy is comparable to the available work volume by the case study vessel with the fully fueled LNG tank. In case of MGO, 860 kg/m<sup>3</sup> of density formulates 344 tons of mass at fully tanked condition [39]. With 42.7 MJ/kg of LHV, MGO fuel provides 1.47 <sup>×</sup> 10<sup>7</sup> MJ of energy [40]. To provide 1.0 <sup>×</sup> 107 MJ of energy, 204 tons of LNG is required. In case of MGO, 234 tons of MGO is required for the same energy output. Table 1 summarizes the property of LNG and MGO. The sulphur content of the LNG fuel is assumed to be zero while the MGO fuel contains 0.1% (m/m) of sulphur.


**Table 1.** Properties and LHV of fuels and required quantity of fuels.
