Verified by DNV, the LCA quantifies GHG emissions and savings across the pilot’s entire carbon value chain, tracing CO2 captured and liquefied on an ocean-going container vessel to ship-to-ship and ship-to-truck transfers, overland transport, and its utilisation at an industrial facility.
There, the CO2 was used as a feedstock to recycle steel slag into post-carbonated slag (PCS) and produce precipitated calcium carbonate (PCC) through carbon mineralisation, a process in which captured CO2 is chemically converted into stable carbonates, fixing carbon long term.
The study found that GHG emissions savings potential rises substantially when logistics and operational inefficiencies in Project CAPTURED are addressed. CO2 utilisation can outperform permanent storage in GHG emissions savings when avoided emissions from displaced carbon are taken into account. It also raised concerns about current life cycle assessment (LCA) guidelines risking undervaluing utilisation pathways.
Professor Lynn Loo, CEO of GCMD, said, “Project CAPTURED 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.”
OCCS as a mid-term decarbonisation pathway – and why LCA matters
Onboard carbon capture and storage (OCCS) is increasingly recognised as a promising mid-term pathway to reduce emissions from vessels that continue to rely on conventional fuels.
By capturing CO2 from exhaust gases, OCCS can significantly reduce onboard fuel-combustion (“tank-to-wake”) emissions. However, its true contribution to decarbonisation must be evaluated across the entire carbon value chain, including its final utilisation and/ or permanent storage.
An LCA quantifies these full-chain GHG impacts transparently and systematically, evaluating that emissions savings achieved onboard are not offset by upstream or downstream burdens.
Scenarios evaluated
The study presents a detailed LCA of the carbon value chain demonstrated in Project CAPTURED. Building on this baseline, the study also examined two hypothetical scenarios, one in which the inefficiencies associated with the first-time pilot are addressed and another in which captured CO2 is permanently sequestered in an offshore reservoir.
In the utilisation scenarios, producing PCC with captured CO2 displaces conventional carbon-intensive production methods, while the use of PCS replaces standard sintering materials in steelmaking, resulting in a reduction of emissions that would have otherwise been released (“avoided emissions”).
GHG emissions savings demonstrated
Project CAPTURED, with OCCS operating at a 10.7% capture rate, demonstrated 7.9% GHG emissions savings across the entire carbon value chain. This corresponds to 0.84 tonnes of CO2 savings realised per tonne of CO2 captured and offloaded from the vessel.
These savings were achieved despite several operational constraints, including the absence of a waste heat recovery system onboard that increased the fuel penalty, long-distance overland truck transport, as well as CO2 venting during offloading and handling.
When these inefficiencies are addressed, GHG emissions savings increase markedly to 17.8%, equivalent to approximately two tonnes of CO2 avoided per tonne of CO2 captured and offloaded from the vessel.
CO2 utilisation can avoid more GHG emissions than permanent storage
The study found that the specific CO2 mineralisation pathway in this pilot outperforms permanent storage.
At comparable capture rates of 40%, mineralising CO2 yields 34% GHG emissions savings, compared with 21% if CO2 were sequestered in an offshore reservoir. When the value chain is optimised, this gap widens further, with the total GHG emissions savings rising to 68-71% depending on whether the PCS produced is used in steel sintering or in concrete production (See figure).
This comparison reveals that CO2 utilisation by carbon mineralisation can deliver greater overall climate benefits than permanent storage when captured CO2 is durably fixed over extended periods, defined under the EU ETS as 100 years or more, and as in the case of PCC that is used in construction.
Current GHG accounting frameworks understate the benefits of CO2 utilisation
At present, the IMO’s GHG accounting frameworks—including its Data Collection System, Carbon Intensity Indicator, and LCA guidelines—do not recognise or account for avoided emissions from when highly emissive conventional products are displaced by captured CO2-derived counterparts.
As a result, the environmental benefits of CO2 utilisation pathways risk being systematically underestimated in formal reporting, despite their potential to avoid more emissions across the wider value chain.
