Toward zero-emission ferries: integrating systematic review and bibliometric analysis insights on alternative fuels and policies

The shipping industry aims to achieve full decarbonization at the European Union (EU) level by mid-century. Over the past decade, various alternative fuels have been explored to address this goal. However, challenges such as insufficient bunkering infrastructure, technological immaturity, and high costs have made shipowners hesitant to invest in “clean” propulsion systems. This study conducts a bibliometric analysis, supported by a systematic literature review, to map and critically synthesize current knowledge on alternative fuels for ferry decarbonization and their alignment with emissions reduction policies. Using the Greek ferry fleet as a representative case study, the paper evaluates the regulatory framework and technical characteristics of various fuel options and examines their compatibility with different vessel categories. A qualitative comparative framework is introduced to link policy types with alternative fuel pathways, offering original insights into policy—fuel alignment. The findings highlight methanol and green electricity (battery-electric systems) as highly promising solutions, especially if battery technologies further advance in the coming years. Hydrogen also presents significant potential, but is currently limited by high production costs and infrastructure requirements. Rather than presenting a quantitative decision-making model this review establishes the conceptual basis for such a framework in future research. This paper also offers innovative proposals to accelerate the adoption of zero-emission fuels, addresses key gaps in existing research, and provides insights for advancing ferry decarbonization.