As the global shipping industry responds to tightening environmental regulations, the Carbon Intensity Indicator (CII) introduced by the International Maritime Organization (IMO) has become a central focus. Designed to monitor and reduce a ship’s greenhouse gas emissions per ton-mile, CII directly impacts how vessels are operated, maintained, and evaluated.

One of the most effective—and often underutilized—methods of improving a vessel’s CII rating is routine hull cleaning. Why? Because hull fouling can increase fuel consumption significantly, and cleaning the hull can reduce fuel oil consumption by up to 25%.

The Impact of Hull Fouling on Emissions and Efficiency
Marine growth on a vessel’s hull—such as algae, barnacles, and slime—creates additional drag as the ship moves through water. This increased resistance forces the engines to work harder, resulting in higher fuel consumption and increased carbon dioxide emissions.

Even light fouling can increase fuel consumption by 5–10%, while heavy biofouling can cause spikes of 20–25% or more. In CII terms, this translates to higher emissions per mile—a direct penalty to the ship’s carbon intensity score.

Why Hull Cleaning Matters for CII Compliance
CII ratings range from A (best) to E (worst), and ships rated D for three consecutive years or E for a single year must submit a plan for corrective action. Poor CII ratings can lead to reduced market competitiveness, limited access to charters, and increased regulatory scrutiny.

Hull cleaning is a low-cost, high-impact way to improve your CII score:

✅ Up to 25% reduction in fuel oil consumption

✅ Significant decrease in CO₂ emissions

✅ Improved vessel speed and operational efficiency

✅ Extended life of antifouling coatings

✅ Better compliance with EEXI, CII, and SEEMP requirements

Proactive Maintenance Is Key
Incorporating hull cleaning into a regular maintenance schedule is not just reactive—it’s strategic. Monitoring vessel performance and cleaning frequency can ensure you stay ahead of fouling before it becomes a problem. Some operators are now integrating performance monitoring tools with cleaning plans to maintain peak efficiency year-round.

Conclusion
In an era of rising fuel costs and strict environmental benchmarks, hull cleaning offers one of the most cost-effective ways to reduce emissions and maintain compliance with the IMO’s CII framework. By minimizing hull resistance and optimizing performance, shipowners can realize fuel savings of up to 25%, all while improving their environmental footprint and marketability.

For fleet managers, technical superintendents, and ship operators, the message is clear: Hull cleaning isn’t optional—it’s essential.