Operational and environmental impact analysis of slow steaming on alternative fuels

This study examines the operational performance of engines powered by alternative fuels under slow steaming, focusing on MAN 5G50ME engines. It evaluates marine diesel oil (MDO), liquefied natural gas (LNG), methanol, and liquefied petroleum gas (LPG) across diverse vessel types, considering compliance with EEXI and CII regulations, global warming potential (GWP), and cost-effectiveness. Key findings indicate that LNG can achieve a 55.1% reduction in GWP20 emissions during slow steaming, while LPG demonstrates the highest cost-benefit ratio (CBR) of 131 USD/tonCO₂eq at 75% SMCR. Although methanol performs better than MDO environmentally, its higher costs make it less desirable. The study highlights trade-offs between reduced fuel costs, increased maintenance, and CAPEX, impacting cost-benefit outcomes. The findings suggest that a comprehensive analysis, including running costs and cargo freight, supports informed decision-making. The importance of slow steaming is emphasised, particularly for bulk carriers after 2029 due to MDO usage. Reducing SMCR to 50% is a potential strategy to ensure regulatory compliance and optimise efficiency. This study provides insights into the trade-offs associated with slow steaming and alternative fuels, contributing to more informed choices within the maritime industry.