Operational Guide · Registers & Logbooks

# Onboard Carbon Capture and Storage (OCCS)

Onboard carbon capture already exists technically, but still counts for nothing toward EEXI or CII: the full regulatory framework is not expected before 2028, a gap holding back large-scale adoption.

OCCS carbon capture CII decarbonization MEPC

## Operational Explanation

Onboard Carbon Capture and Storage (OCCS) captures CO2 from engine exhaust gas, compressing and storing it on board for offloading ashore at a dedicated facility. The technology is now "ship-ready" for some applications, but faces a significant regulatory gap: IMO's short-term measures (EEDI, EEXI, CII) currently give no credit for CO2 captured on board, a gap identified as a major brake on its commercial-scale adoption.

The MEPC has adopted a work plan to develop a complete OCCS regulatory framework, with finalization expected by 2028; meanwhile, guidelines for testing, surveying, certifying and approving OCCS systems are under discussion at a correspondence group, and OCCS is in any case listed among the potentially relevant lower-intensity energy sources under the greenhouse gas fuel intensity targets envisaged by the IMO Net-Zero Framework.

## Regulatory Reference

No complete IMO OCCS framework yet: the MEPC is developing guidelines for testing, surveying, certifying and approving OCCS systems, with finalization of the overall regulatory framework expected by 2028; OCCS is mentioned as a potentially relevant energy option under the IMO Net-Zero Framework, without yet receiving credit under the EEDI/EEXI/CII measures.

## Scope of Application

Ships installing CO2 capture systems from exhaust gas, with onboard storage pending offloading ashore; the technology is currently more mature for retrofit applications on large ships with available storage space.

## Procedure / How to Complete It

1. Assess the technical feasibility of an OCCS installation in relation to the space available on board for storing captured CO2 and the existing exhaust gas configuration.
2. Do not rely on an EEXI/CII regulatory credit for captured CO2, since IMO's short-term measures do not yet recognize it in their current form.
3. Monitor the development of IMO guidelines for testing, surveying, certifying and approving OCCS systems at the dedicated correspondence group.
4. Plan logistical arrangements for offloading stored CO2 ashore, verifying the availability of receiving facilities at usual ports of call.
5. Consider OCCS as part of a multi-lever decarbonization strategy, not as an isolated substitute for other efficiency measures already required (SEEMP, CII).

## Practical Example

Example: a large ship installs a retrofit OCCS system capturing a significant portion of CO2 from exhaust gas during voyages, storing it in dedicated tanks for offloading ashore at ports equipped with receiving facilities; the owner does not, however, count on a direct improvement in the CII rating, pending completion of the dedicated regulatory framework expected by 2028.

## Real Cases

OCCS technology reached a maturity level described as "ship-ready" by some industry sources in 2026, with pilot installations already operational; however the gap between technological maturity and regulatory recognition remains a central theme of the IMO debate, since owners investing in OCCS today receive no direct benefit under the short-term efficiency measures currently in force.

## Common Mistakes Mistake Library

Mistake | Consequence | How to avoid it
--- | --- | ---
Investment in an OCCS system based on the expectation of an immediate EEXI or CII credit | Disappointed regulatory expectations, since the credit is not currently recognized by IMO's short-term measures | Assess the OCCS investment based on the overall decarbonization strategy, not on an immediate regulatory benefit that does not yet exist
OCCS installation planned without verifying the availability of CO2 receiving facilities at usual ports of call | Logistical difficulties offloading captured CO2 | Verify the availability of CO2 receiving infrastructure on planned operating routes before investing
No monitoring of the development of IMO OCCS guidelines under way | Installed systems that may not align with future certification requirements | Actively follow the development of the OCCS regulatory framework at the dedicated IMO correspondence group

## PSC Observations

OCCS is not yet subject to dedicated PSC verification, in the absence of a complete IMO regulatory framework; the situation is expected to evolve with the finalization of testing, surveying and certification guidelines expected by 2028.

## Operational Tips

- Do not expect an immediate EEXI or CII regulatory credit for installing an OCCS system: the dedicated framework is still under development.
- Always verify the availability of onshore CO2 receiving facilities on planned operating routes before investing in an OCCS system.
- Follow the development of the dedicated IMO guidelines, since the complete regulatory framework is expected only by 2028.

## Checklist

- Technical feasibility of onboard CO2 storage space verified
- Regulatory expectations aligned with the current absence of EEXI/CII credit for OCCS
- Development of IMO OCCS guidelines actively monitored
- Availability of CO2 receiving facilities verified at usual ports of call
- Overall decarbonization strategy integrating OCCS with other already-required measures (SEEMP, CII)

## FAQ

Does OCCS automatically improve the ship's CII rating?
No, currently IMO's short-term measures (EEDI, EEXI, CII) give no credit for CO2 captured on board: this is a known regulatory gap, pending the complete OCCS framework expected by 2028.
When will the IMO regulatory framework for OCCS be completed?
The MEPC has adopted a work plan with finalization expected by 2028; meanwhile, guidelines for testing, surveying, certifying and approving OCCS systems are under discussion.
Is OCCS already a mature technology?
Some industry sources now describe it as 'ship-ready' in 2026, with operational pilot installations, but technological maturity remains ahead of current regulatory recognition.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

## Related Topics

IMO Net-Zero Framework CII (Carbon Intensity Indicator)

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