Slow Steaming as a Sustainable Measure for Low-Carbon Maritime Transport

Reducing greenhouse gas (GHG) emissions is essential across all sectors, including the maritime transport industry. Speed reduction is a key short-term operational measure for lowering GHG emissions from ships, and its implementation has already begun. While speed reduction offers significant benefits, particularly in terms of GHG emissions reduction potential, there are concerns about its application, including increased voyage times, an increase in the number of ships required, and the fact that ships may operate in conditions quite different from those for which they were designed and optimized. This study investigates the impact of speed reduction on ship performance in calm water, using a post-Panamax container ship as an example. Numerical simulations of resistance, open-water, and self-propulsion tests were conducted for a full-scale ship and propeller, and the results were validated against extrapolated towing tank data. Hydrodynamic characteristics, fuel consumption, and carbon dioxide emissions at various speeds were then estimated. The results indicated that when constant transport work was maintained, yearly CO₂ emissions decreased by −16.89% with a 10% speed reduction, −21.97% with a 20% speed reduction, and −25.74% with a 30% speed reduction. This study demonstrates that the classical cubic law for fuel oil consumption and speed dependence is not valid, as the speed exponent is lower than 3. The potential benefits and drawbacks of implementing slow steaming are discussed. Finally, this research contributes to the existing literature by evaluating the CO₂ emissions reduction potential of slow steaming.

Nastia Degiuli, Ivana Martić, Carlo Giorgio Grlj