Navigating the IMO Carbon Intensity Indicator – What Shipowners Need to Know for 2023 and Beyond

Executive summary

The IMO Carbon Intensity Indicator (CII) framework measures the annual operational carbon intensity of ships to encourage emissions reduction. By integrating operational efficiency measures, performance monitoring, and voyage optimization strategies, shipowners can proactively manage compliance, improve fleet performance, and strengthen their position in a decarbonizing maritime market.

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1. Understanding the IMO Carbon Intensity Indicator (CII)

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The CII is a regulatory framework introduced by the IMO under the MARPOL Annex VI amendments, designed to track the annual carbon intensity of vessels. It calculates carbon intensity based on CO₂ emissions per transport work (grams CO₂ per tonne-nautical mile). Ships are assigned an annual rating from A to E, with A being the most efficient. Ratings are used to identify underperforming vessels and drive operational improvements (Lloyd's Register).

To determine a vessel's CII, the following data is required:

· Fuel consumption (in tonnes)

· Distance traveled (in nautical miles)

· Deadweight tonnage (DWT) or gross tonnage (GT)

This data is collected under the IMO Data Collection System (DCS) and reported annually (ClassNK).

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2. Compliance Timeline and Reporting

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· 2023: CII requirements apply to all ships ≥5,000 GT engaged in international voyages.

· Annual reporting: Ships must submit verified carbon intensity ratings to the IMO.

· Corrective measures: Vessels receiving a “D” or “E” rating must develop an improvement plan to avoid downgrading in subsequent years (Lloyd's Register).

Adopting operational efficiency and voyage optimization strategies early can help maintain higher CII ratings, reduce corrective measures, and lower potential operational costs.

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3. Key Drivers of Carbon Intensity

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Several factors directly influence a ship’s CII rating:

· Fuel consumption and type: Lower carbon fuels or energy-efficient fuels reduce emissions per transport work.

· Speed and voyage management: Optimized routing and adaptive speed management contribute to fuel savings. Deploy on longer routes

· Cargo utilization: Maximizing cargo carried per voyage improves carbon intensity metrics.

· Hull and machinery condition: Regular maintenance and upgrades impact overall vessel performance.

Understanding these drivers allows shipowners to target specific operational improvements for maximum impact on CII ratings.

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4. Operational Efficiency Measures and Technology Impact

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To enhance CII performance, shipowners can adopt a mix of operational and technological measures:

· Voyage Optimization Platforms: AI and predictive analytics for route planning, weather adjustments, and fuel-efficient speeds.

· Energy Management Systems (EMS): Monitor engine and fuel efficiency across vessels for fleet-wide performance insights.

· Hull and Propeller Enhancements: Reduce drag and improve propulsion efficiency or add wind assisted propulsion to the vessel

· Electrical efficiency: Reduce the load on the generators by adding technologies that helps reduce the electrical consumption onboard.

· Waste Heat Recovery Systems (WHRS): Capture and reuse energy from engines to reduce fuel consumption.

· Hybrid and Battery-Assisted Propulsion: Reduce emissions during low-speed or port operations.

By integrating these solutions, operators can improve their CII rating, enhance operational efficiency, and better manage regulatory risk without necessarily requiring major fleet overhauls.

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5. Strategic Implications for Shipowners

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The CII framework incentivizes shipowners to focus on operational performance and data-driven decision-making:

· Fleet Performance Monitoring: Continuously track vessel CII ratings and operational metrics.

· Operational Adjustments: Implement route planning, speed optimization, and maintenance scheduling.

· Technology Assessment: Evaluate solutions that reduce fuel consumption and emissions.

Proactively addressing these areas supports compliance, strengthens sustainability credentials, and enhances competitiveness in chartering and financing markets.

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6. Conclusion

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By continuously monitoring fleet performance against the CII framework and implementing targeted operational strategies as well as implementing commercially viable Energy efficiency Technologies, shipowners can maintain regulatory compliance while improving voyage outcomes and long-term operational resilience.

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