A new study has found that carbon capture technology aboard ships could be the key to decarbonising the shipping industry – and even removing carbon from the atmosphere – but that uptake of this technology is currently bottlenecked by low port readiness. 

The research study, Concept study to offload onboard captured CO₂, was prepared by global class society Lloyd’s Register and international engineering company, Arup, and commissioned by the Global Centre for Maritime Decarbonisation.

Global interest in onboard carbon capture and storage

Global shipping has experienced a surging interest in Onboard Carbon Capture and Storage (OCCS), with approximately 60 per cent of the respondents to the Global Centre for Maritime Decarbonisation’s (GCMD) recent decarbonisation survey indicating that onboard capture will be an important part of the green transition, with 50 per cent of the ‘frontrunners’ (those organisations that the GCMD considers have the greatest decarbonisation ambitions and have dedicated substantial resources to reducing emissions) declaring an intention to pilot onboard capture as early as 2025. 

Meanwhile, international ship broker, Clarksons Research, has reported that more than 30 vessels in the current fleet, alongside another 22 newbuilds, are or will be testing this technology.

GMCD has said that OCCS remains a nascent decarbonisation solution. 

“Its commercial adoption hinges on the identification of pathways by which onboard captured CO₂ can be offloaded and a clear articulation of the fate of the captured CO₂, i.e., how it is ultimately used or sequestered,” the GMCD said.

Global class society and technology research group, DNV, reported that there are many mature technologies for the capture of CO₂ from industrial exhaust. 

After fuel is burnt, the exhaust gas is sent through a system that contains chemicals called “amines” – these are basically ammonia (NH₃) that have had the hydrogen replaced with other chemicals. The currently most widely used form is monoethanolamine, according to DNV. 

These amines are included in a water-solution, which is brought into contact with the exhaust gases. There, the amines weakly bond with carbon dioxide to form intermediate compounds. The now carbon-rich solution is sent through a heating process that separates the chemicals – releasing almost pure carbon dioxide. The CO₂ is then sent through a dehydrator to drive off the water. The amines will undergo further treatment to be recycled back into the system. The CO₂ is then compressed into a liquid-like state.

Ultimately, the recovered carbon could either be sequestered in underground rock formations or put to industrial uses such as the manufacture of synthetic fuels.

Most efficient system

Storing, moving, handling, and offloading captured CO₂ is best done when CO₂ is in liquid form; it’s the most efficient and cost-effective method. 

“Limited by port readiness and existing infrastructure, the study identified ship-to-terminal transfer of ISO tank containers holding liquefied CO₂ as the easiest modality to pilot today,” the GMCD study said.

The GMCD report found that, although a small number of ports have the infrastructure to offload liquefied CO₂, they are primarily designed to handle food-grade CO₂, which limits the interoperability of facilities to handle onboard capture CO₂. 

The study examined more than ten infrastructure projects worldwide that are likely to handle large volumes from CO₂ emitting industrial clusters. It was found that port infrastructure needed for offloading, storing and transporting onboard captured CO₂ will likely need to be integrated with such projects for economies of scale. However, many of the projects had not reached the point of a Final Investment Decision, and so, ports have not proceeded with offloading infrastructure.

“Furthermore, introducing liquid CO₂ (LCO₂) offloading into already complex port operations will likely impact port efficiency and operational performance. The need for additional buffer zones to address the safety concerns of LCO₂ handling and storage will also add to existing space constraints at ports and terminals,” the study said.

The report found that Ship-to-Ship and Ship-to-Shore transfers using an intermediate LCO₂ receiving vessel are the most promising modalities for offloading at scale. Ship-to-Terminal transfer of captured CO₂ confined in ISO tank containers can be used at smaller scales and for end uses that require higher grades of CO₂.

Regulatory and policy aspects

The GMCD report said that the policy and regulatory landscape for offloading of CO₂ is immature and that the London Protocol, which provides a regulatory framework for CO₂ transport and related carbon credits between countries, does not cover the transfer of CO₂ captured in international waters to a country. Meanwhile, the main international maritime pollution treaty, MARPOL, does not account for onboard captured CO₂ as a waste stream. 

Standards for measuring and recognising collected and transferred CO₂, along with monitoring, reporting and verification need to be developed. It was noted in the report that the IMO is looking to implement a market-based measure in 2027 that will incorporate technical and economic elements, which will put a price on CO₂ emissions.

“The effectiveness of OCCS for maritime decarbonisation hinges on successfully integrating carbon capture solutions onboard ships and offloading the captured CO₂ to the onshore carbon capture, utilisation and storage (CCUS) value chain.” 

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