The Effect of Icebreaker Assistance on the Attained Carbon Intensity Indicator of a Merchant Ship Operating in the Northern Baltic Sea

Abstract In response to carbon intensity regulations established by the International Maritime Organization (IMO), the modern shipping industry is increasingly adopting innovative technologies, novel ship designs and sustainable operational practices to reduce the carbon intensity of the global shipping fleet. Current regulatory instruments, such as the Carbon Intensity Indicator (CII) and the Energy Efficiency Design Index (EEDI), evaluate carbon intensity of a ship based on its performance in open water. Consequently, compliant solutions commonly involve reduction of engine power and optimization of the hull form for more efficient open-water performance. It has been debated that this trend has led to an increased demand in icebreaking assistance among the modern ice-going merchant ships. Moreover, since carbon emissions produced while sailing in ice are excluded from the CII framework, the effects of ice-going capabilities and icebreaker assistance on the operational carbon intensity of the merchant ships remain unaddressed. This paper presents a theoretical transit analysis assessing the influence of operational practices of ice navigation on the annual attained CII of merchant ships engaged in a regular service in the northern Baltic Sea. The study finds inverse correlation between the ice-going capabilities of common bow designs and overall annual attained CII of the merchant ship and the assisting icebreaker. The impact of the icebreaker emissions is also discussed. Altogether, the analysis highlights the limitations of the current CII framework. The need for further refinement of the CII framework to account for ice navigation and icebreaker emissions is discussed, with recommendations made for ensuring a more accurate and fair representation of the operational carbon intensity of ice-going ships.