IMO Rules Understate Benefits of Utilising Captured Carbon, Says GCMD

Global Centre for Maritime Decarbonisation (GCMD) carbon capture pilot project demonstrates greenhouse gas emissions savings potential along with regulatory hurdle.

January 7, 2026

The emissions reductions impact of deploying carbon capture technologies in the maritime industry may be understated using accounting methods recommended by the International Maritime Organization (IMO) guidelines, limiting incentives for shipowners to invest in such systems, according to a new report.

The regulatory issue was one of the findings of a GCMD report on its pilot project to demonstrate a full value chain for onboard capture carbon dioxide; the project involved the capture and offload of over 25 tonnes of CO2 on Evergreen Marine Corporation containership Ever Top.

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Using an attributional lifecycle analysis (LCA) of the project’s carbon value chain gave a net greenhouse gas (GHG) emissions increase of 8.6% across the value chain when compared to a baseline of not using onboard carbon capture and storage (OCCS). The attributional LCA looks at the carbon value chain from a shipowner’s perspective and its scope ends at utilisation of the carbon, assuming the CO2 will be permanently stored, thus omitting the full impact of utilisation in end products.

The carbon captured onboard Ever Top was used as feedstock to recycle steel slag into post-carbonated slag (PCS) and precipitated calcium carbonate (PCC). PCC is a common component in the production of building materials like concrete — its usual production methods involve a carbon-intensive process using limestone.

Using a consequential LCA, which accounts for emissions avoided through the displacement of carbon-intensive materials in end products by those produced with captured carbon, emissions savings were 7.9% across the value chain.

“Under the current attributional treatment recommended in the IMO guidelines, utilisation pathways can appear to deliver no emissions savings because avoided emissions from product displacement are excluded. This in turn provides no incentive for shipowners and operators to invest in the substantial capital expenditure and operational expenses required to deploy OCCS,” the report said.

Efficiency improvements

Analysis of the pilot scheme identified several inefficiencies that had limited GHG emissions savings across the value chain, inefficiencies that could be addressed in future OCCS deployments.

The lack of a waste heat recovery system onboard Ever Top meant the fuel penalty when running the OCCS system was 5%, compared to 1.5% if a waste heat recovery system had been in place. Transport and logistics emissions for the value chain were high, including 26% from hose purging and 52% from the 2,200 km overland transport of the captured liquid CO2 by truck from port to processing plant.

Eliminating these and other “first-time” inefficiencies, by installing a waste heat recovery system and transporting the LCO2 overland by pipeline, boosts the emissions savings using a consequential LCA from 7.9% to 17.8%, the report said.

GCMD assessed the GHG savings of its value chain against permanent storage of the captured CO2. In a hypothetical scenario where onboard carbon capture rates are boosted to 40%, carbon capture and permanent storage leads to emissions savings of 21%, while utilisation of the captured carbon brings 34% emissions savings.

Professor Lynn Loo, CEO of GCMD, said the project “shows that onboard carbon capture, when thoughtfully integrated with utilisation pathways, can deliver real emissions reductions today while we continue to scale up low- and zero-carbon fuels. It also highlights how we measure and account for those reductions matter. If our frameworks continue to ignore avoided emissions and displaced carbon, we risk disincentivising investments in solutions that can meaningfully bend the emissions curve.”