Carbon capture, utilization, and storage (CCUS) is a combination of technologies for managing CO2 emissions. CCUS includes technologies that capture CO2 from sources of CO2 emissions and either store it in sequestered locations or convert it into other useful materials to prevent the release of CO2 into the atmosphere. CCUS has a long history, and the technologies to capture, transport, utilize and store CO2 are relatively mature compared to other alternative fuels, so it can be applied to conventional systems without major modifications. Onboard carbon capture and storage (OCCS) is the application of CCUS technologies to a ship, to reduce the CO2 emissions from a ship to the atmosphere by capturing and storing CO2 onboard. OCCS also faces the challenges of a lack of regulation, high energy consumption, high costs, and insufficient infrastructure for offloading and transporting CO2 to a final storage site. Nevertheless, to extend the lifetime of existing ships using fossil fuels and as a part of supply chains for sustainable alternative fuels, OCCS needs to be considered as a bridge technology to get through the transitional period until the era of fully sustainable alternative fuels arrives.