CO2-emissions reduction potential of LNG compared with conventional fossil fuels and the influence of port manoeuvres

This study evaluated the CO 2 -emission reduction potential of liquefied natural gas (LNG) in maritime transport and examined the influence of vessel operational profiles on emissions performance. A roll-on/roll-off passenger case study indicated an estimated 17.07% reduction in CO 2 emissions using LNG relative to conventional-fuel use, which was lower than the 25%–30% reduction reported previously. To investigate this discrepancy, eight tanker vessels covering a combined distance of more than 1.77 million nautical miles were analysed. The results indicated an estimated CO 2 -emission reduction of ∼ 25% using LNG during long-distance operations, whereas frequent port calls, manoeuvring and auxiliary-engine use substantially reduced the estimated emission-reduction benefit. Additionally, annual distance sailed and CO 2 emissions were analysed for each vessel, yielding average emission rates of 0.196 t CO 2 /mile for coastal vessels and 0.499 t CO 2 /mile for Suezmax vessels. These findings indicate that operational factors play an important role in decarbonisation outcomes and highlight the need to combine fuel-transition policies with operational and port-based measures.