A comprehensive review of post-combustion CO2 capture technologies for applications in the maritime sector: A focus on adsorbent materials

Onboard carbon capture systems are among the most promising strategies for decarbonization of the maritime sector in the short and medium term. These systems are based on post-combustion technologies, such as absorption, adsorption, calcium looping, membrane separation, and cryogenic technologies. They can be installed on existing ships without conflicting with other available carbon mitigation measures. Temperature Swing Adsorption (TSA) is one of the most proficient solutions; however, for effective use in the maritime sector, it is crucial to investigate adsorbent materials that are suitable for the specific conditions of flue gas deriving from ship engines. To this aim, attention should be focused on those materials that have i) high CO2 adsorption capacities per unit of volume due to the expected space limitations on board ships, ii) good performances at relatively high temperatures in the presence of water and other chemical species (such as sulphur and nitrogen oxides and particulate matter), iii) easy regeneration patterns and iv) ideally highest possible efficiencies. This paper provides an overview of the existing post-combustion technologies, focusing on their key technical aspects. Subsequently, starting from observing the great potentiality of TSA processes, a review of potential adsorbents for CO2 capture in the maritime sector is reported. Functionalized materials, mainly with amines or potassium carbonate, show superior performance and are the most suitable option for on board ship applications. Ultimately, the paper aims to establish a baseline for possible TSA-based carbon capture applications in the maritime sector and stimulate further research in designing optimized CO2 adsorption processes.