By Abbas Nazil
A major trial by the Global Centre for Maritime Decarbonisation has shown that shipboard carbon capture delivers negligible climate benefits and cannot meaningfully reduce shipping emissions.
The findings are based on Project CAPTURED, a full life cycle assessment that tracked captured carbon dioxide from ship exhaust through storage, transport and final processing.
The study is significant because it relied on real-world pilot data rather than theoretical modelling.
A vessel burning very low sulphur fuel oil was fitted with an onboard carbon capture system and monitored across its entire operational chain.
The system achieved a gross capture rate of only 10.7 percent, far below levels needed for deep emissions cuts.
Captured carbon dioxide was liquefied, stored onboard, transferred between ships, transported long distances and processed through mineralisation pathways.
All energy use, losses, venting and transport emissions were fully accounted for in the assessment.
The independently reviewed analysis found that the net lifecycle greenhouse gas reduction was just 7.9 percent.
Without downstream accounting credits, the value chain failed to break even and in some cases increased emissions.
Under attributional accounting, which is used by regulators, the utilisation pathway resulted in higher emissions than operating without capture.
Even when higher capture rates were modelled, the results showed only modest improvements.
At a hypothetical 40 percent capture rate, permanent storage delivered a lifecycle reduction of about 21 percent.
Researchers noted that such conditions are unlikely to be achievable at scale.
The report highlights that shipping requires deep and rapid emissions reductions to align with international climate targets.
Single-digit or low double-digit reductions were described as marginal efficiency gains rather than viable transition pathways.
The assessment found that onboard carbon capture adds significant energy penalties.
Capturing, compressing and liquefying carbon dioxide required an additional fuel penalty of about five to six percent.
That extra fuel use directly increased upstream emissions and reduced propulsion efficiency.
The study also identified major storage losses, with around 28 percent of captured carbon dioxide remaining in tanks after offloading.
Additional emissions occurred through venting during transfers and transport.
The physical realities of carbon dioxide storage were found to severely limit scalability.
Liquefied carbon dioxide occupies several times the volume of the fuel that produces it.
Long voyages accumulate excessive volumes of waste carbon dioxide that displace cargo and affect vessel stability.
Transporting captured carbon dioxide proved especially emissions-intensive.
The pilot involved trucking carbon dioxide more than 2,000 kilometres, generating emissions that erased much of the capture benefit.
Ports currently lack the pipelines, storage hubs and sequestration facilities needed to reduce these losses.
The report concludes that onboard carbon capture only appears viable under optimistic assumptions and alternative accounting frameworks.
Researchers warned that such assumptions are unlikely to survive regulatory scrutiny.
The findings suggest shipboard carbon capture is a technological dead end rather than a bridge to decarbonisation.
Cleaner alternatives such as electrification, efficiency improvements and sustainable fuels already offer far greater emissions reductions.
The study shows that complexity, cost and physics all work against onboard carbon capture in maritime shipping.
Experts say the evidence should redirect investment and policy away from ineffective solutions toward proven low-carbon pathways.
