**6. Conclusions**

The key research findings can be summarized as below.

Using LNG as a marine fuel was proven as an effective fuel in reducing the marine pollutant, compared to conventional marine petroleum fuels including MGO. In particular, Case 1 (LNG import from Qatar) was revealed the best option based on that all environmental impact categories were marked the lowest, compared to other cases. The emission quantities for Case 1 were presented as below:

	- 1. AP: 1.76 tonnages of SO2 equivalent per 1.0 <sup>×</sup> 107 MJ of fuel consumption;
	- 2. EP: 1.18 tonnages of N equivalent per 1.0 <sup>×</sup> 107 MJ of fuel consumption;
	- 3. POCP: 4.28 tonnages of NMVOC equivalent per 1.0 <sup>×</sup> <sup>10</sup><sup>7</sup> MJ of fuel consumption;
	- 4. PM: 26 kg of PM2.5 equivalent per 1.0 <sup>×</sup> 107 MJ of fuel consumption.

Moreover, considering factor-based findings, Case 1, LNG from Middle East to South Korea, was determined to produce 0.88 times lesser GWP compared to Case 3, MGO from Middle East to South Korea while Case 2, LNG from U.S. to South Korea, emitted 0.86 times lesser GWP than Case 4, MGO from U.S. to South Korea.


**Author Contributions:** Conceptualization, B.J. and S.H.; methodology, B.J., S.H., and M.K.; software, S.H.; formal analysis, investigation, S.H.; resources, B.J. and S.H.; writing, B.J., S.H., and M.K.; review and editing, M.K. and P.Z.; visualization, S.H.; supervision, M.K., K.J., P.Z.; funding acquisition, K.J.; project administration, B.J. and K.J.

**Funding:** This research is supported by Pusan National University (PNU) Korea-UK Global Program in Offshore Engineering (N0001288) funded by the Korean Ministry of Trade, Industry and Energy.

**Acknowledgments:** The authors would like to express their gratitude to ILSHIN shipping CO., Ltd. and Korean Register of Shipping for their invaluable support, comments and suggestions. They have contributed considerably to this study.

**Conflicts of Interest:** The authors declare no conflict of interest.
