Evaluation of marine B24 biofuel emission performance and CO2 reduction potential in large ocean-going vessels

Biofuels provide a 'drop-in' solution to reduce compliance costs under the International Maritime Organization's (IMO) Net Zero Framework while advancing net-zero greenhouse gas (GHG) emission goals. In this study, we conducted a sea trial using marine B24 biofuel in a large ocean-going vessel, systematically comparing emission performance between low-sulfur residual heavy fuel oil (LSHFO) and B24 in the vessel's low-speed main engine. Using IMO-endorsed methods, we calculated emission intensities and factors for NOx and CO2, offering empirical validation for IMO decarbonization policies. Results demonstrate that B24 reduces CO2 concentrations at the exhaust by 1.0-2.5% (tank-to-wake, TTW) under 50-65% engine load. On a well-to-wake (WTW) lifecycle basis, B24 achieves a 25.63% reduction in total CO2 emissions, outperforming conventional fossil fuels. NOx emissions from B24 comply with IMO Tier II standards, confirming regulatory feasibility. This study presents the first real-world, full-lifecycle GHG assessment of marine B24 biofuel in large-vessel operations, based on a complete long-distance voyage with a low-speed main engine. The findings validate operational safety and emission benefits, supporting broader adoption of low- and zero-carbon marine fuels in maritime decarbonization.