ClassNK maps project path for onboard carbon capture

By Elena Vasquez

ClassNK has released a project-wide onboard carbon capture handbook that builds on Edition 2.0 safety and technical guidelines and extends the scope to CO2 infrastructure, regulation and emissions accounting.

What problem does the handbook solve?

The “Onboard Carbon Capture Systems Implementation Framework” is the latest addition to ClassNK’s Handbook on Ship GHG Emissions Evaluation series. The classification society says the publication gives shipowners, operators and other stakeholders practical guidance for considering OCCS across an entire project. It also aims to help relevant parties discuss whether a specific project can proceed.

ClassNK puts the central issue plainly: “The introduction of OCCS requires consideration not only of the value chain from onboard CO₂ capture through to storage and other forms of final treatment, but also of mechanisms for quantifying and verifying emissions reductions.”

That chain starts with exhaust gas. An OCCS system captures CO2 from a ship’s exhaust, processes it and stores it temporarily on board. ClassNK notes that the approach has drawn attention as a way to support maritime greenhouse-gas reductions, alongside demonstration projects and international discussions on regulatory frameworks.

Why doesn’t capture alone reduce emissions?

The maritime sector already has a broad decarbonisation menu: operational improvements, energy-efficiency technology and a transition to alternative fuels. OCCS adds another route, but it does not stand alone.

ClassNK’s warning is equally direct: “However, translating the use of OCCS into actual emissions reductions requires more than the onboard system itself.”

The distinction is concrete for practitioners. Shipboard equipment handles the capture and temporary-storage step; the wider project must secure routes for unloading and transportation, then arrange storage, sequestration or utilisation of the captured CO2. It must also establish mechanisms to quantify and verify the resulting emissions reductions.

In practical terms, a vessel can have the capture unit while still lacking the downstream route and accounting structure. ClassNK says technology, infrastructure, regulation and emissions-reduction assessment all require a project-wide view, which is why the handbook brings those four perspectives together.

What do MRV and chain of custody add?

The handbook gives special attention to two systems that track different parts of the proposition.

• Monitoring, reporting and verification (MRV) provides continuous monitoring, reporting and verification of emissions or emissions reductions.
• Chain of custody (CoC) provides for transferring, tracking and managing captured CO2 and its associated attribute information at each stage of the supply chain.

These mechanisms matter because the environmental result depends on more than the ship’s equipment performance. Operators need to manage and document captured CO2 through its downstream chain while establishing a method for measuring the claimed reduction. The handbook supports stakeholder discussions and assessment of individual OCCS projects; ClassNK does not present it as project approval or a new compliance requirement.

How does the framework build on ClassNK’s earlier work?

ClassNK says its “Guidelines for Onboard CO₂ Capture and Storage Systems” established safety and technical requirements for these systems. The classification society also cites knowledge accumulated through demonstration projects and experience gained through greenhouse-gas certification services as inputs to the new handbook.

A related ClassNK release identifies Edition 2.0 of those guidelines as world-first requirements for onboard CO2 capture systems using the membrane separation method. The new implementation framework draws on that safety and technical base, then widens the lens to the infrastructure, regulatory and verification questions surrounding specific projects.

That distinction keeps the documents complementary. The guidelines address what an onboard capture-and-storage system must do; the framework asks how that system fits into an end-to-end CO2 chain and how the claimed reduction can be measured and trusted.

Where is the handbook available?

Shipowners, operators and other stakeholders can find the publication on ClassNK’s website at www.classnk.or.jp, following Information Services and then ClassNK Transition Support Services. The handbook also appears under “Technical Publication” in ClassNK MyPage.

ClassNK says it will continue supporting maritime decarbonisation by providing relevant information. The announcement provides no shipboard capacity target, installation deadline or mandatory adoption date.

What decides what happens next?

For a specific vessel, the next gate is downstream coordination: identify a workable route for unloading, transportation and final storage, sequestration or utilisation of captured CO2, and put credible MRV and CoC arrangements in place. ClassNK’s framework does not choose a route or declare a vessel ready to proceed; it gives stakeholders the project-wide test they must apply.

The deciding milestone is whether a proposed shipboard system can connect to a secure CO2 route and produce verifiable emissions reductions. Without both, ClassNK says, the onboard system alone cannot turn captured exhaust carbon into a demonstrated climate benefit.