The growing importance of marine carbon capture in shipping
Retrofitting carbon capture solutions onto ships is an emerging yet vital technology to diminish carbon emissions within the maritime sector. This process involves equipping ships with systems capable of capturing CO₂ emissions directly from the engine's exhaust, thereby preventing their release into the atmosphere.
Global shipping increasingly prioritises marine carbon capture as regulatory demands tighten and sustainable shipping gains momentum. This technology offers a crucial pathway to compliance with emissions standards while supporting greener operations.
Technical challenges in implementing carbon capture onboard ships
However, implementing these systems poses design challenges, including limited onboard space, the need for compatibility with existing engines, and potential structural adjustments to accommodate new equipment. These considerations underscore the importance of innovative engineering and precise integration to ensure effective, scalable carbon capture solutions for the maritime sector.
Onboard carbon capture could significantly contribute to the maritime industry's decarbonisation efforts. However, it presents design and integration challenges that must be addressed. Understanding the full scope of retrofitting implications is crucial, as it encompasses system-wide technical and compliance considerations, including planning, procurement, engineering, installation, commissioning, operation, and training.
Operational considerations and prospects of carbon capture across maritime
For carbon capture systems to be installed, ongoing monitoring and maintenance during voyages are essential, accompanied by appropriate crew training to continue operating such installations safely and efficiently. Considering the aforementioned fact, carbon capture systems could make ship performance and fuel efficiency dependent upon systematic checks for the optimal functioning of such systems.
Improved retrofitting technologies and research in the future might provide even greater efficiencies and cost reductions than currently realised. If the industry continues to evolve towards further integration, such innovations may ease processes and lead to scalable and sustainable emission reductions in shipping.
Compliance and regulatory requirements for carbon capture in shipping
Adherence to international regulations, such as the IMO's GHG Strategy, is essential. Working toward these standards will help shipping companies avoid penalties and keep their operations legitimate when there is increased pressure from environmental regulations.
As carbon intensity indicators and targets for emissions reduction become increasingly stringent, integrating approved carbon capture solutions becomes crucial to managing sustainability operations. The information at this hub is invaluable for gaining insights into the technical, economic, and operational aspects of carbon capture retrofitting.
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FAQs for Retrofit Research programme – Onboard Carbon Capture and Storage (oCCS)
Onboard carbon capture and storage (oCCS) refers to technologies that use chemical processes to remove/separate CO2 (or carbon “C”) from a single, identifiable entity from which CO2 (or carbon “C”) originates. These technologies are mainly classified according to the stage at which carbon is separated from the fuel stream or combustion products:
- Pre-combustion: Carbon is captured before fuel oxidation based on different fuel processing methods (output is always H2 which can be used as fuel)
- Post-combustion: Carbon is captured after fuel oxidation from the exhaust gas stream (before it is released into the atmosphere)
- Oxy-fuel combustion: Fuel is oxidised in pure or oxygen-rich environment (rather than air) resulting in “clean” exhaust gas (water vapour + pure CO2)
The captured CO₂ (or carbon “C”) is then stored onboard and offloaded for transport, utilisation or permanent storage. oCCS is being explored as a ship CO2 reduction technology that could help reduce maritime CO2 emissions from newbuilds and existing vessels while supporting the continued use of both conventional and alternative marine fuels.
Post-combustion onboard carbon capture systems remove carbon dioxide (CO₂) from engine and boiler exhaust gases using different carbon capture technologies. The most mature technology for the maritime industry is chemical absorption. More specifically:
- Chemical absorption is a type of absorption, which is a chemical or physical process by which chemicals in one state become absorbed by chemicals in another state (e.g., gases absorbed by a liquid or solid). In this process, a fluid (the absorbate) dissolves into or permeates a liquid or solid medium (the absorbent).
The captured CO₂ is then separated from the exhaust stream, processed, compressed or liquefied, and stored in dedicated onboard tanks. Once the vessel reaches a suitable port, the CO₂ can be discharged for transport, utilisation or permanent storage as part of the wider carbon capture, utilisation and storage (CCUS) value chain. The overall effectiveness of oCCS depends not only on capture performance onboard but also on the availability of suitable infrastructure to receive and manage the captured CO₂ ashore.
Focusing on post-combustion and chemical absorption systems, they can potentially be retrofitted to existing ships, although suitability depends on factors such as vessel type, available space for modifications and oCCS equipment installation, power requirements, operational profile and the required size of onboard CO₂ storage capacity.
In addition to the capture system itself, vessels must accommodate associated equipment, piping and storage tanks for CO₂ including offloading equipment, which can affect space availability and vessel operations. For example, ships operating on fixed routes with access to suitable CO₂ reception facilities may be better positioned to adopt oCCS than vessels undertaking long voyages without reliable offloading infrastructure.
A vessel-specific technical and economic assessment is therefore required to determine feasibility, costs, operational implications and potential emissions reductions.
The main challenges of oCCS include the space required onboard for carbon capture equipment and CO₂ storage tanks, the additional energy needed to operate the system relative to the CO2 capture rate (%), installation costs (CAPEX), annual operational costs (OPEX), safety and ventilation criteria that need to be met, and the availability of port and terminal infrastructure to receive captured CO₂.
These factors can increase total fuel consumption, reduce cargo capacity and impact vessel operations, particularly where onboard CO₂ storage requirements are significant or offloading infrastructure is limited. Wider adoption will also depend on continued technological development, supportive maritime regulations, and the expansion of carbon transport and storage networks.
Onboard carbon capture systems can help reduce shipping CO2 emissions by capturing a proportion of the carbon dioxide (CO₂) produced during fuel combustion before it is released into the atmosphere (referring specifically to post-combustion chemical absorption systems).
The level of emissions reduction achieved depends on factors such as gross CO2 capture rate %, energy requirements to operate the oCCS system, CO2 leakage rates (%) and how the captured CO₂ is transported and stored after discharge.
While oCCS does not eliminate emissions at source, it has the potential to reduce CO2 emissions from existing vessels without requiring a complete change in fuel or propulsion and power generation systems. For this reason, it is being considered as one of several technologies that could support maritime decarbonisation alongside energy efficiency measures, alternative marine fuels and operational improvements.
Onboard carbon capture systems could provide a transitional decarbonisation pathway for some vessels, particularly where low-GHG intensity or zero-GHG emission fuels, supporting infrastructure or fleet replacement are not yet practical.
It may help reduce greenhouse gas (GHG) emissions from existing ships, support compliance with evolving environmental requirements, and complement other measures such as energy efficiency retrofits, voyage optimisation and alternative marine fuels.
Rather than being a standalone solution, oCCS is generally viewed as one element of a broader decarbonisation strategy. Its long-term role in achieving net-zero GHG shipping will depend on factors including technology development, commercial viability, regulation, infrastructure and the availability of carbon transport and storage networks, with adoption likely to vary by ship type, trade and operating profile.
