The IMO's Sub-Committee on Carriage of Cargoes and Containers (CCC 12) has started drafting interim safety guidelines for on-board carbon capture and storage (OCCS) systems, with final approval targeted for 2029 — leaving shipowners facing at least four years of vessel-by-vessel approvals before a common international framework exists.

The sub-committee aims to finalize the guidelines in 2028 and secure approval in 2029, when they will enter force as non-mandatory recommendations rather than binding rules. Until adoption, OCCS projects will rely primarily on vessel-specific risk assessments and approvals from flag administrations and classification societies.

What will the first guidelines cover?

The framework will set out general objectives and functional safety requirements without mandating a specific technology. CCC 12 expects to address chemical absorption capture systems first, with other capture methods to follow.

According to the IMO's work plan, the guidelines will span the entire OCCS chain:

• CO2 capture and processing
• Compression and on-board storage
• Monitoring
• Transfer to shore at port offloading points

The rules will account for risks to the ship and crew, including CO2 asphyxiation hazards and the dangers posed by chemicals used in the capture process. No amendments to the IMDG Code are planned, because the necessary safety rules will be developed within the specific OCCS guidelines themselves.

Why is the timeline so long?

The guidelines remain in their early stages by design. The IMO's stated primary objective at this point is to gather sufficient practical experience and operating evidence to form the basis for reliable, technology-neutral regulations.

That sequencing reflects the state of the technology. OCCS is under consideration as a retrofit option for the existing fleet, but its applicability depends not only on capture efficiency. Operators must also weigh energy requirements, available space on board, storage capacity, the vessel's route, and — critically — the availability of infrastructure to receive and manage captured CO2 at ports.

For early movers, implementation means evaluating every aspect of the system: integration with the vessel, design, stability, crew safety, maintenance, and CO2 transfer arrangements.

What the safety framework will not decide

The IMO's work addresses safety, not economics. Unresolved questions extend well beyond the sub-committee's mandate, including:

• Emissions accounting and verification for captured CO2
• CO2 storage and utilization pathways
• Recognition of OCCS within international and regional climate frameworks

The IMO itself notes that while its work will establish the necessary common safety framework, it will not in itself determine the economic and environmental viability of deploying OCCS. That verdict will come from market signals — CO2 offtake infrastructure, carbon accounting rules, and the cost of retrofitting against alternative compliance routes.

The parallel commercial track is already moving. BIMCO has launched the first standard contract for CO2 shipping, and Northern Lights has expanded its CO2 carrier fleet with a third vessel, building out the reception and transport infrastructure that OCCS-equipped ships will depend on.

What happens next

The decisive milestone is the 2028 finalization of the interim guidelines and their 2029 approval as non-mandatory recommendations. Watch for CCC sessions in the interim to produce draft text on chemical absorption systems, and for early retrofit projects — operating under flag administration and class approvals — to generate the operational evidence that will shape whether the guidelines harden into mandatory rules later.