The potential of onboard carbon capture on ships

To achieve the International Maritime Organization’s target of net-zero greenhouse gas emissions by 2050, the industry will need to utilise alternative fuels and a range of emission-reducing technologies. At the forefront of these is carbon capture and storage (CSS). While CCS is not an alternative to electrification or renewable energy sources, it is a necessary tool for cutting emissions in sectors that are hard to decarbonise.

Carbon capture involves trapping carbon dioxide (CO₂) emissions at the source and preventing them from entering the atmosphere. The captured CO₂ is then either stored in geological formations, such as depleted oil and gas fields or saline aquifers, that can provide secure storage for millennia, or it is used in industrial processes, a concept known as carbon capture, utilisation and storage (CCUS).

Onboard carbon capture(OCC) includes various technologies to capture CO₂ emissions from ships during operation. OCC typically relies on post-combustion methods, where the CO₂ is separated after fuel combustion.

Marine carbon capture systems are designed to capture CO₂ directly from a ship’s exhaust gases. The captured CO₂ is then compressed, liquefied and stored onboard in tanks for later offloading at ports equipped with appropriate storage infrastructure. Given that shipping alone accounts for approximately 3 per cent of global CO₂ emissions, the potential impact of this technology is substantial.

Several methods for capturing emissions are being explored for maritime applications, each with their own advantages and challenges:

This is the most common method, involving the use of chemicals (such as amines) to absorb CO₂ from exhaust gases. It is highly effective but energy intensive.

This method uses semi-permeable membranes to separate CO₂ from other gases. It is less energy intensive than other methods but is still in the preliminary stages of development for marine applications.

The cryogenic process cools exhaust gases to extremely low temperatures, causing the CO₂ to condense and separate. It is effective but requires significant energy input.

These methods highlight the complexity of achieving carbon neutrality, as each comes with trade-offs in terms of energy use and operational costs.

Due to their size and energy demands, cruise ships are notorious for high emissions. Although implementing onboard carbon capture on ships has the potential to significantly reduce cruise ship carbon emissions, it is not without its challenges. The energy required to run carbon capture systems could increase a ship’s overall fuel consumption, creating a trade-off between emissions reduction and fuel efficiency. However, with further advances, carbon capture could be an effective solution to make carbon-neutral ships a reality.

The integration of onboard systems for carbon capture with port infrastructure is crucial to achieving the maritime industry’s climate goals. For carbon-neutral ships to become the norm, the industry must collaborate to build the necessary infrastructure for CO₂ offloading, storage and transportation.

Innovative technologies must be thoroughly evaluated before they can become commercially viable alternatives. The world’s most advanced test arena for CO₂ capture systems is the state-of-the-art Technology Centre Mongstad (TCM) in Norway. The most advanced amine technologies in the market have all been tested at TCM.

As technology and regulatory frameworks evolve, carbon capture techniques will likely become more widespread. Although challenges remain, onboard carbon capture systems could become a standard feature on ships by mid-century.