A new life cycle assessment (LCA) published by the Global Centre for Maritime Decarbonisation (GCMD) has found that onboard carbon capture and storage (OCCS) can deliver meaningful greenhouse gas (GHG) emissions savings when assessed across the full carbon value chain.
Verified by DNV, the LCA evaluated emissions from Project CAPTURED, the world’s first demonstration of ship-to-ship offloading of onboard captured and liquefied CO2 (LCO2) with downstream utilization. The pilot, completed in June 2025, traced captured CO2 from an ocean-going container vessel through ship-to-ship and ship-to-truck transfers, overland transport, and final industrial use.
In the project, captured CO2 was used as a feedstock in carbon mineralization processes to recycle steel slag into post-carbonated slag and produce precipitated calcium carbonate (PCC), permanently fixing carbon in stable mineral forms.
OCCS assessed beyond the vessel
GCMD said the findings highlight the importance of assessing OCCS beyond onboard fuel-combustion emissions alone. While OCCS reduces “tank-to-wake” emissions, its climate impact depends on emissions across capture, transport, utilization and storage.
At a capture rate of 10.7%, Project CAPTURED achieved a 7.9% reduction in GHG emissions across the full value chain, equivalent to 0.84 tons of CO2 avoided per ton captured and offloaded.
These results were achieved despite operational constraints typical of a first-of-a-kind pilot, including additional fuel use, long-distance transport and CO2 venting during handling.
Relevant: U.S. Sinks Global Shipping Carbon Tax After Threatening Sanctions
When these inefficiencies are addressed, GCMD found emissions savings could rise to 17.8%, or nearly two tons of CO2 avoided per ton captured.
The LCA also compared CO2 utilization with permanent storage. At comparable capture rates, carbon mineralization delivered greater overall emissions reductions than offshore sequestration, particularly when displaced emissions from conventional materials production were included. In optimized scenarios, total emissions savings reached as high as 68-71%.
GCMD noted that current maritime GHG accounting frameworks do not recognize avoided emissions from CO2 utilization, potentially understating the climate value of such pathways and slowing investment in scalable decarbonization solutions for shipping.
Read more: China Installs First Centrifugal Onboard Carbon Capture On Bulk Carrier
