Project CAPTURED: Demonstrate the offloading, handling, utilisation and/or permanent storage of onboard captured CO₂

To demonstrate ship-to-ship (StS) liquefied CO₂ (LCO₂) offloading operation at Yangshan Deepwater Port, Shanghai, and the utilisation of onboard captured CO₂ to recycle steel slag and produce post-carbonated slag (PCS) and precipitated calcium carbonate (PCC)

• Conduct safety studies for transferring LCO₂ and develop an emergency response plan

• Conduct ship compatibility assessment for LCO₂ transfers

• Identify compliance pathways for offloading onboard captured CO₂ from international vessels

• Conduct life cycle assessment (LCA) of greenhouse gas (GHG) emissions associated with onboard carbon capture and storage (OCCS) across the carbon value chain

Part 1 – Technical, operational, and regulatory learnings from the first end-to-end demonstration of onboard captured CO₂ utilisation

The pilot confirmed both the technical and operational feasibility of integrating maritime carbon capture into an industrial CO₂ utilisation pathway, effectively linking shipping decarbonisation efforts with heavy industry’s demand for low-carbon feedstocks. Several key highlights include:

• Tracked quality and quantity of CO₂: Comprehensive sampling and analysis were carried out to monitor the quality and transferred volumes of LCO₂ across the value chain. Across all custody transfer points, CO₂ purity exceeded 99.95 vol%, meeting the downstream user’s specifications.

• Safe and controlled operations ensured: Operations were conducted after rigorous hazard identification, mooring analysis and LCO₂ leak assessment, with multi-zone access controls. Handling and transfer of LCO₂ followed procedures adapted from existing liquefied natural gas and liquefied petroleum gas transfer protocols. No safety incidents occurred during the trial.

• Regulatory hurdles overcame: Early authority engagement allowed for the one-off, project-specific reclassification of captured CO₂ from “hazardous waste” to “hazardous cargo”, enabling lawful land transport and industrial utilisation under Chinese regulations.

• Commercial viability demonstrated: The captured CO₂ was successfully mineralised into PCC, a high-value functional filler used in products, such as paper, plastic, paint, and building materials, as well as PCS as sintering material for steel production or supplementary cementitious material (SCM).

Looking ahead, the learnings from the pilot highlight that scaling the carbon value chain will require:

• Adapting policies and regulations: Classifying high-purity captured CO₂ as “hazardous cargo” will be essential to enable lawful land transport and industrial utilisation at scale.

• Improving commercial viability: Co-locating offloading and utilisation sites, expanding industrial partnerships, and promoting CO₂-derived product markets can increase the commercial drive for carbon capture.

• Streamlining operations: Key steps include aligning tank capacities and transfer volumes as well as enhancing transfer equipment insulation to reduce CO₂ vaporisation, installing custody transfer-grade flow meters and inline gas analysers to monitor CO₂ quality, and standardising safety protocols, such as emergency shutdown interfaces and mooring configurations.

Part 2 – Quantifying the life cycle emissions of the onboard captured CO₂ value chain: From ship-to-ship offloading and transport to utilisation

This part of the project involved a detailed LCA of the carbon value chain, demonstrated in the pilot. 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”). Several key highlights include:

• 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 finds 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.

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.