A comprehensive review on countermeasures for CO2 emissions from ships

As a highly efficient mode of freight transport for global trade, international shipping is currently expected to improve energy efficiency and reduce carbon emissions. Various countermeasures and action plans have been proposed by stakeholders in the maritime community. This paper presents a comprehensive review to categorise the pathways and highlight the concepts, methodologies, characteristics, implementation barriers and future prospects of different abatement measures for carbon dioxide emissions in the maritime industry. In addition, the regulatory framework composed of rules and regulations, market-based measures and voluntary actions is reviewed and discussed. The literature reviewed is selective and critical considering papers from reputable journals and reports from leading institutions or organisations. It was found that most of the technological and operational measures were highly context-sensitive and no individual measure in isolation could achieve the objectives of low carbon or zero carbon shipping. Eco-friendly fuels and alternative power sources were found to be promising but their applications would significantly depend on ship types and ship routes, i.e., diversification and decentralization of ship power sources and marine fuel types are inevitable for future shipping. It was also shown that the economic considerations and legal framework are still the main challenges at present. This review has clarified the pathways to decarbonisation in the shipping industry and it is expected to be a useful resource for academic research and industrial practice.