The Carbon Intensity Indicator (CII) regulation is a short-term measure of IMO for reducing GHG emissions from ships. In addition, the 2023 IMO GHG Strategy describes that the CII regulation is anticipated to create a potential synergy effect with other measures. Accordingly, the CII regulation, which took effect in 2023, is forecast to increasingly impact international shipping and the commercial vessel market. However, efforts to improve energy efficiency and implement slow steaming for ships are insufficient to meet the CII regulation that is increasingly stringent over time. Therefore, there is a growing need for fundamental improvements in future response strategies. In this study, major causes of low CII ratings for ships were investigated from a recent consulting project that was conducted to support shipping companies in satisfying the regulation from operational and technical perspectives. Lastly, proposals to implement the CII regulation effectively and to reduce GHG emissions from ships fundamentally were made, taking into account the major causes derived from the consulting.

The rapid adoption of alternative marine fuels has introduced safety challenges not fully addressed by regulatory frameworks developed for conventional fuels. This study examines how International Maritime Organization (IMO) safety regulations respond to the dominant risk characteristics of alternative fuels, focusing on LNG, LPG, methanol, and ammonia. A comparative analysis is conducted based on physicochemical properties, hazard pathways, and corresponding provisions under the IGF Code and Interim Guidelines. The results show that while the IGF Code provides a goal-based, flammability-centered framework, its extension to fuels with different risk profiles—such as toxicity and liquid-phase hazards—creates structural mismatches between dominant hazards and regulatory trigger mechanisms. In particular, reliance on flammability-based indicators (e.g., LEL) for safety system activation in toxicity-dominant fuels reveals a misalignment between regulatory assumptions and actual risk pathways. In addition, intensified conservatism in ammonia regulations enhances safety but raises challenges related to operability and regulatory predictability. The study concludes that future regulatory development should adopt an integrated framework aligning hazard-specific indicators with regulatory mechanisms and incorporating empirical evidence through the Experience Building Phase (EBP).