Underestimated penalty of hull fouling: A scenario-based analysis of GHG emissions from global shipping

A ship's hydrodynamic performance is fundamental to her operational efficiency, yet it is significantly degraded by hull fouling. The significant fuel penalty from hull fouling represents a critical operational challenge, but it is often underestimated. This is frequently due to focus on direct maintenance costs and off-hire periods, or the recent emphasis on other energy-saving devices, which leads to a gap in quantifying the performance loss from the hull condition itself. To systematically quantify this penalty, this study performs a scenario-based analysis on 52,636 vessels across six major ship types. By integrating Granville's similarity law for added resistance with dynamic fouling growth models and vessel-specific operational profiles, we estimate the emission penalties for the global fleet. Findings reveal that moderate fouling can increase annual fuel consumption and GHG emissions by an average of 20–30 %. Notably, large container ships, tankers, and bulk carriers are identified as 'global hotspots' accounting for the majority of these emissions. For instance, a single large container ship with a capacity over 15,000 TEU can emit as much as 20,000 tons of additional CO2 annually due to hull fouling. This study provides quantitative evidence that proactive hull management is a fundamental lever for enhancing ship hydrodynamic performance and, consequently, a highly effective and immediate decarbonization measure.