Techno-economic and environmental assessment of Onboard Carbon Capture for maritime net-zero compliance

The shipping sector faces mounting pressure to align with the International Maritime Organization's (IMO) revised greenhouse gas (GHG) strategy targeting net-zero emissions by 2050. Although zero- and near-zero (ZnZ) emission fuels may offer long-term solutions, their large-scale deployment is constrained by cost, infrastructure, efficacy and safety concerns. Onboard Carbon Capture and Storage (OCCS) systems may provide a transitional approach, and this study assesses the techno-economic and environmental feasibility of across four container vessel types powered by Marine Diesel Oil (MDO), liquefied natural gas (LNG), and methanol. Two OCC technologies-chemical absorption using monoethanolamine (MEA) and cryogenic separation-are evaluated in terms of energy demand, space requirements, lifecycle GHG emissions, and economic performance under the IMO's Net-Zero Framework. Results show that MEA-based systems offer the highest GHG reduction potential (up to 41.5 % for MDO) but at the cost of increased fuel consumption (15-30 %) and cargo capacity penalties (∼10 %). Cryogenic systems enhance safety but are more energy-intensive due to reliance on auxiliary power. OCC-equipped vessels can meet IMO GHG intensity targets through 2035, particularly when combined with biofuels, and provide up to a 2.2-fold cost advantage over purchasing Remedial Units (RUs). Although not a permanent solution, OCC offers a practical bridge toward maritime decarbonisation. Deployment requires policy support, port and geostorage infrastructure, and further innovation in capture technologies and waste heat integration.