The Carbon Intensity Indicator (CII) is an IMO-mandated measure of a ship's operational carbon efficiency. It indicates how efficiently a ship transports cargo while emitting carbon dioxide (CO₂). The CII is calculated annually using the following formula:
$$Attained\:CII=\frac{Annual\:CO_2\:Emissions\:\left(g\right)}{Capacity\times Distance\:Sailed\:\left(nmi\right)}$$
Based on the attained value, every ship is assigned an annual CII rating from:
- A – Superior performance
- B – Minor superior
- C – Moderate
- D – Minor inferior
- E – Inferior performance
The CII rating provides a standardized method of evaluating a ship's carbon efficiency. Under IMO regulations, the required CII limits become progressively stricter each year until 2030, encouraging ship operators to continuously improve energy efficiency, reduce fuel consumption, lower CO₂ emissions, and minimize the overall carbon footprint of shipping.
Under the Ship Energy Efficiency Management Plan (SEEMP), the Second Engineer plays a vital role in ensuring compliance with CII requirements by supervising engine room operations and implementing measures that improve fuel efficiency and reduce CO₂ emissions.
The following operational strategies and maintenance practices help improve a ship's CII rating:
- Operate the main engine at the optimum "eco-speed" and appropriate engine load to significantly reduce daily fuel consumption and CO₂ emissions.
- Regularly calibrate and maintain fuel injection equipment, including fuel injectors and fuel pumps, and optimize valve timing to ensure efficient combustion and lower fuel consumption.
- Coordinate with the deck department to carry out periodic hull cleaning and propeller polishing, thereby reducing hull resistance and improving propulsion efficiency.
- Operate the Shaft Generator (PTO) instead of diesel generators whenever possible. Maintain Variable Frequency Drives (VFDs) on engine room pumps to reduce electrical power consumption.
- Ensure the Exhaust Gas Economizer (EGE) and jacket water heat recovery systems operate efficiently to maximize waste heat utilization, thereby reducing boiler fuel consumption and the running hours of auxiliary machinery.