Impacts of IMO Mid-term GHG Reduction Measures on OCCS and Future Response Strategies

Abstract

In April 2025, the 83rd session of the Marine Environment Protection Committee (MEPC) of the International Maritime Organization (IMO) officially approved a package of mid-term greenhouse gas (GHG) reduction measures to help achieve net-zero emissions from international shipping by or around, i.e. close to, 2050, as outlined in the 2023 IMO GHG Strategy. Among these, the introduction of the Goal-based Fuel Standard (GFS), which regulates the GHG intensity of marine fuels through GHG Fuel Intensity (GFI) Compliance Approach, is expected to serve as a pivotal driver for maritime decarbonization. These measures are scheduled for formal adoption at MEPC ES.2 in October 2025 and are anticipated to enter into force from March 2027. While Member States broadly support the transition to carbon-neutral and zero-emission fuels, many recognize the current limitations in technology readiness, fuel availability, and supporting infrastructure for fuels such as green ammonia and e-methanol. In response to these constraints, Onboard Carbon Capture and Storage (OCCS) is gaining attention as a complementary solution, particularly for ships operating on conventional fossil fuels. OCCS was identified as a key enabler in achieving the 2050 net-zero target under Task 2 (Fleet Impact Assessment) of the IMO’s Comprehensive Impact Assessment. Since 2021, the Republic of Korea has continuously proposed the inclusion of OCCS within the IMO GHG regulatory framework. As a result, an OCCS Correspondence Group (CG) was established in May 2024, tasked with developing a work plan for regulatory development. The CG’s work plan comprises five major tasks, including environmental risk management, legal and logistical coordination for CO2 handling, compatibility between ships and onshore reception facilities, data collection and reporting, and incentive mechanisms. Among these, the most contentious issue is the integration of OCCS’s GHG mitigation effects into existing IMO instruments such as the Energy Efficiency Design Index (EEDI), the Energy Efficiency Existing Ship Index (EEXI), and the Carbon Intensity Indicator (CII). Proponents argue that OCCS provides measurable emissions reductions that should be recognized under these frameworks, while others emphasize the need for full life-cycle accounting and traceable CO2 storage before credit is granted. This presentation examines the impacts of the IMO’s mid-term GHG reduction measures on OCCS and explores key discussions within the MEPC concerning regulatory and technical challenges. It further evaluates strategic pathways for ensuring that OCCS is appropriately recognized within the IMO’s decarbonization framework. Special emphasis is placed on the potential role of OCCS in the forthcoming “Zero or Near-Zero (ZNZ) Fuels and Technologies” reward system, as well as its integration within flexible compliance mechanisms. By analyzing the regulatory timeline, Member State positions, and recent technological advancements, the presentation provides practical insights and policy recommendations to support the adoption of OCCS as a credible and effective solution for decarbonizing international shipping.