Fuel Consumption by ContainershipsFuel consumption by a containership is mostly a function of ship size and cruising speed, which follows an exponential function above 14 knots. So an 8,000 TEU containership consumes 225 tons of bunker fuel per day at 24 knots, but at 21 knots consumption drops to 150 tons per day, a 33% decline. While shipping lines would prefer consuming the least amount of fuel by adopting lower speeds, this advantage must be mitigated with longer shipping times as well as assigning more ships on a pendulum service to maintain the same port call frequency. The main ship speed classes are:
Normal (20-25 knots; 37.0 – 46.3 km/hr). Represents the optimal cruising speed a containership and its engine have been designed to travel at. It also reflects the hydrodynamic limits of the hull to perform within acceptable fuel consumption levels. Most containerships are designed to travel at speeds around 24 knots.
Slow steaming (18-20 knots; 33.3 – 37.0 km/hr). Running ship engines below capacity to save fuel consumption, but at the expense a additional travel time, particularly over long distances (compounding effect). This is likely to become the dominant operational speed as more than 50% of the global container shipping capacity was operating under such conditions as of 2011.
Extra slow steaming (15-18 knots; 27.8 – 33.3 km/hr). Also known as super slow steaming or economical speed. A substantial decline in speed for the purpose of achieving a minimal level of fuel consumption while still maintaining a commercial service. Can be applied on specific short distance routes.
Minimal cost (12-15 knots; 22.2 – 27.8 km/hr). The lowest speed technically possible, since lower speeds do not lead to any significant additional fuel economy. The level of service is however commercially unacceptable, so it is unlikely that maritime shipping companies would adopt such speeds.
In an environment of higher fossil fuel prices, maritime shipping companies are opting for slow steaming for cost cutting purposes. The ongoing practice of slow steaming is likely to have an impact on supply chain management, maritime routes and the use of transshipment hubs.Source: adapted from Notteboom, T. and P. Carriou (2009) “Fuel surcharge practices of container shipping lines: Is it about cost recovery or revenue making?”. Proceedings of the 2009 International Association of Maritime Economists (IAME) Conference, June, Copenhagen, Denmark.