Sustainable retrofitting for shipping: Assessing LNG dual fuel impact on global warming potential through life cycle assessment

Recently, the International Maritime Organization (IMO) introduced an initial strategy aiming to reduce and ultimately achieve net-zero greenhouse gas emissions by 2050. While various research projects on retrofitting have been conducted, there is a noticeable gap in detailed studies concerning emission reduction through liquefied natural gas (LNG) dual-fuel retrofit options. This study assesses the feasibility and environmental impacts of applying LNG dual-fuel retrofit to a 9196 gross tonnage training ship. It explores replacement scenarios of 20 %, 30 %, and 40 % LNG incorporation using life cycle assessment. Additionally, the study employs a life cycle assessment methodology to compare the global warming potential against both the life cycle assessment database and engine emission factors. Over 35 d of operation at a normal continuous rating of 85 % power load, replacing 20 %, 30 %, and 40 % of fuel with LNG resulted in a reduction of global warming potential by approximately 23.1 %, 32.7 %, and 42.3 %, respectively. These results indicate that LNG replacement cases significantly lower emissions related to global warming potential compared to conventional marine diesel oil (MDO) operations, with greater reductions observed at higher replacement percentages. Further investigation revealed significant differences between the results derived from the life cycle assessment database and engine emission factors. However, statistical analyses indicated that both sources exhibit a consistent trend, with p-values in all power load cases exceeding 0.05, indicating no significant interaction term. Despite notable differences, the utilization of life cycle assessment offers high reliability and ease of use, serving as a solid foundation for decision-making regarding sustainable options.