Reviewing two decades of cleaner alternative marine fuels: Towards IMO's decarbonization of the maritime transport sector

Due to the growing concerns of emissions from the shipping industry, the International Maritime Organization (IMO) has set strategies to reduce the CO2 intensity by 40% in 2030 and cut total GHGs emissions by at least 50% by 2050, with 2008 as a baseline. Clean alternative marine fuels are widely recognized and used as a viable solution for reducing ship-related air pollution. Several studies including traditional reviews have been conducted to examine the literature on cleaner alternative marine fuels and their role in decarbonizing the shipping sector. However, these studies fail to unpack the main research actors, evolutionary nuances, and emerging research hotspots in this field. To quantitatively and qualitatively explore this research field, the current study adopts a bibliometric analysis. 583 eligible documents published from 2000 to 2020 were retrieved and merged from the Web of Science Core Collection and Scopus databases, and analyzed with the R-studio bibliometrix package (Biblioshiny). Results revealed that the field is growing significantly at a growth rate of 15.8%, with key contributions to the field originating from the USA. Liquified Natural Gas has been identified as the most researched alternative shipping fuel. However, recent trends show researchers turning their attention towards methanol, ammonia, and hydrogen fuels. By analyzing the frequently used keywords and relevant articles, it became clear that the research community has focused mainly on the potential of different alternative fuels as a replacement to conventional marine fuels to limit the emissions from the shipping sector from an environmental, technical, and economic perspective. The current study offers a basis for future research into the decarbonization of the shipping industry. [Display omitted] •Bibliometric study on clean marine fuels based on Web of Science and Scopus databases.•A growing research field with an annual growth rate of 15.8%.•Key authors, institutions and countries in the field have been identified.•LNG emerged as the most researched alternative shipping fuel.•Research hotspots and trends on clean marine fuels discussed.