The shipping industry is under increasing pressure to act upon the IMO target to reduce its GHG by 50 % by 2050 and is showing a growing interest in on board post-combustion carbon capture & storage (CCS), a novel concept that allows for decarbonizing the vessel while still keeping the same engine and the same fuel. This study reviewed a total of 27 on board post-combustion CCS projects, mainly feasibility studies. On board CCS is a novel highly promising solution for decarbonizing the maritime sector that was proven to be feasible. The most common on board CO2 capture technology employed was chemical absorption with amine or ammonia scrubber and thermal stripper systems. Other carbon capture technologies applied on board were: chemical absorption with high-gravity rotating packed beds instead of conventional columns, temperature swing chemical adsorption, membrane separation, cryogenic separation and CO2 mineralization. Almost all projects proceeded with on board liquefaction of the captured CO2, which was then temporarily stored on board in suitable tanks and destined for unloading at appropriate facilities at port or off-shore, as part of the global CO2 supply chain. In the CO2 mineralization projects it was limestone (CaCO3) powder, a stable solid marketable product, that was temporarily stored on board. Only 3 projects proposed disposing the captured CO2 directly into the ocean, either in the water column or in-seabed (‘CO2 ocean storage’) or in the form of carbonates (‘Ocean Liming’), which are all currently prohibited by the IMO and deemed highly risky and non-pragmatic in terms of environmental impacts, regulatory implications, poor public acceptance and investment risk. The on board CCS systems performed in principle well in terms of % CO2 capture, cargo penalty, ship stability and trim and the effect of the ship’s movement on the CCS system’s operation. The cost of on board carbon capture was relatively high and expected to decrease with increasing TRL and economies of scale, similarly to other novel maritime decarbonization technologies. There were 3 challenges that were decisive about the on board CCS systems’ performance as successful business cases: (1) energy efficiency (more efficient solvents, heat integration and other energy-saving technologies required), (2) vessel (retro-)fitting potential (compact, light-weight, modular, scalable, containerized, non vessel-specific designs favored) and (3) multi-pollutant removal potential (CO2, SOx, NOx, PM), given that the shipping industry has to abide by several air pollution regulations.
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