The impact of slow steaming on reducing CO2 emissions in the Mediterranean Sea

Abstract

One of the short-term operational measures for reducing CO2 emissions from ships at sea is sailing at reduced speed, i.e. slow steaming. In this study, the benefits of slow steaming are studied using the example of a container ship on a typical sailing route passing through the Mediterranean Sea. Thus, the reduction of fuel consumption and CO2 emissions is assessed in calm water and in waves for the design speed and slow steaming speed. Resistance and propulsion characteristics in calm water are determined by means of computational fluid dynamics based on the viscous flow theory for a full-scale ship. The added resistance in waves is calculated by the potential flow theory. The propeller operating point is determined for the design speed and slow steaming speed and for sea states with the highest probability of occurrence in the Mediterranean Sea. The fuel consumption and CO2 emissions are then calculated for an engine powered by both low sulphur marine gas oil and liquefied natural gas. For the investigated route, the potential reduction in CO2 emissions could be up to 286 t for an engine fuelled by low sulphur marine gas oil and up to 448 t for an engine fuelled by liquefied natural gas.