Existing technologies and scientific advancements to decarbonize shipping by retrofitting

The maritime industry is transporting about 90 % of world commerce, contributing to the global greenhouse gas emissions that cause climate change. Increasing pressure on the sector to reduce its carbon footprint requires developing specialized energy-efficient technologies and studying their compatibility with modern safety and sustainability expectations of the waterborne sector. This research supports the United Nations sustainable development goals SDG 7 (Affordable and clean energy) and 13 (Climate Action), and reviews available technologies for shipping decarbonization through design for retrofitting. Promising research areas to improve the energy efficiency of ships could focus on design concepts and methodologies, fluid dynamics, and artificial intelligence. The study suggests that while individual promising decarbonization technologies are available, a comprehensive and coordinated approach is necessary to decarbonize global shipping efficiently. The study identified three promising paths of ship retrofitting to meet the International Maritime Organization decarbonizing objective 2050, aiming at a 70 % reduction of annual greenhouse gas emissions compared to 2008. The first path – using green energy sources (e.g., ammonia, battery, and methanol) – requires scaling up technologies and developing a regulatory framework and control of the lifecycle of the fuel production process. The second path – using ship-based carbon capture technologies, ship design (e.g., hull retrofitting, air lubrication, and wind-assisted propulsion), and operation solutions (e.g., weather routing and logistics planning) – requires building more CO 2 storage and control of the lifecycle of liquified CO 2 . The third path – using biodiesel as a fuel in combination with ship design and operation solutions – requires extending feedstock for biodiesel production. • Shipping decarbonization by design for retrofitting green technologies is imminent. • Decarbonization is possible via the use of green fuels, carbon capture and storage, and biodiesel production. • The decarbonizing uncertainty level must be considered together with the decarbonizing efficiency. • Academic research areas of relevance are design methods, fluid dynamics, and artificial intelligence.