Onboard carbon capture: modular designs and optimisation

Seabound co-founder and chief executive Alisha Fredriksson, explained that the system’s modular calcium-looping containers are compact second-generation capture units. Ms Fredriksson described a prototype skidded module that attaches to the funnel, with saturated containers rotated ashore for regeneration. Modules can be exchanged in less than a day using standard TEU-handling equipment and incur a cargo-capacity penalty of only 1 to 2%.

Mitsubishi Shipbuilding manager (engineering) Hiromasa Kano then outlined an alternative amine-based system under development for newbuild dual-fuel LNG carriers. This design integrates the CO2 capture train above the main engine platform, employing a heat-pump-assisted reboiler to drive solvent regeneration, thereby reducing steam demand by 25% compared with conventional reboilers. “We aim to limit parasitic loads to below 3% of installed power,” he said. He stressed that compact piping routes and minimised flanged connections were essential to preserve freeboard and maintain stability.

China Classification Society (CCS) technical lead Xiangqian Fang detailed provisional CCS guidance and national standards filling IMO’s regulatory voids. He outlined GB/T 42797-2023 for pipeline transport, GB/T 45121-24 for energy-measurement protocols, and GB/T 45126-25 for slag carbonation testing. MrFang emphasised that risk assessments on an 82,000-dwt bulk carrier under construction targeted forced-ventilation fans, CO2 detectors, freezing controls and emergency shutdown valves to ensure “no unacceptable risks remain” during liquid-CO2 storage and transfer.

Seabound CEO and co-founder Alisha Fredriksson was questioned by GCMD Professor Loo on the type of lime used in the system as the production of lime has its own CO2 costs. Ms Fredriksson noted that the “green lime” used by Seabound was produced by suppliers using low CO2 systems.

DNV consultant Ms Chara Georgopoulou summarised Technology Readiness Level (TRL) of the OCCS.

Technology Readiness Level is a scale — originally developed by NASA — that assesses the maturity of a technology. It runs from 1 to 9:

1. Basic principles observed
2. Technology concept formulated
3. Experimental proof of concept
4. Laboratory validation of component or process
5. Laboratory validation of integrated subsystem
6. Prototype demonstration in relevant environment
7. Prototype demonstration in operational environment
8. Actual system completed and qualified
9. Actual system proven in operational use

Ms Georgopoulou noted that amine absorption, mineralisation and membrane adsorption range from TRL 6 to 9 for maritime applications, while cautioning that “scaling requires supportive infrastructure, business models and regulatory adaptation”. Her overview of emerging STS transfer concepts emphasised the need for custody-transfer meters and inline analyzers to ensure purity and quantify boil-off, as demonstrated by the GCMD-led Project CAPTURED.

Throughout the day, speakers agreed that crew competency and shore-based support are indispensable. Mr Kim highlighted the role of land-based experts in providing real-time remote monitoring to relieve crew workload and ensure safety. Professor Loo added that harmonised training curricula, drawing on LNG and LPG precedents, are under development to prepare officers for novel OCCS operations.

The session closed with a consensus that technical feasibility hinges on space-efficient designs, energy-penalty mitigation and robust operational procedures. Delegates urged early alignment on impurity limits, MRV frameworks and handling pressures to reduce complexity and enable smoother scaling. As the industry advances towards net-zero by 2050, modular OCCS offers a pragmatic retrofit pathway, balancing capex-opex with tangible GHG reductions — all while working within the stringent confines of existing vessel architecture.

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