Shipping is a cornerstone of global transportation responsible for moving large volumes of traded goods. At the same time, negative environmental impacts of shipping operations have attracted growing concerns. Although recognised as the most energy-efficient mode of transportation compared to air and land-based transport, maritime transportation contributes significantly to air-borne emissions, alongside other types of pollutants. Hence, it is apparent that alternatives to highly polluting conventional marine fuels, i.e., crude oil or diesel, have to be found in shipping, just as in other sectors. Responding to calls for a greater attention to actors’ roles in transitions, as well as for broader sectoral coverage of empirical work in the field of sustainability transition studies, this doctoral thesis explores the role of incumbents (established shipping firms) in the early stages of maritime energy transitions. 

Focusing on incumbents is a relatively recent, yet rapidly evolving, stream of research in sustainability transitions studies, with increasing evidence showing heterogeneity and strategic variety in incumbent activities in various transition contexts. By drawing on a multi-level perspective from the socio-technical transition literature, the dynamic capabilities approach from the strategic management literature, and structuration theory, this thesis contributes new knowledge on “how” and “why” frontrunner incumbent shipping firms engage with maritime niche technologies and alternative energy solutions as well as what strategies they adopt to overcome increasing environmental sustainability pressures. These are the topics that have so far received scant attention in sustainability transitions studies. The thesis utilises a qualitative case study approach to study the selection of firms from passenger, vehicle carrier and container shipping business segments that are active in environmental work. 

The findings of this thesis indicate that the roles of shipping firms in the early stage of maritime energy transitions are diverse and more complex than often accounted for in sustainability transitions literature. It is demonstrated that due to increased regulatory, social and competitive pressures, firms’ activities with regards to engagement in maritime niche technologies and alternative energy have shifted from reactive to a mix of strategies where a portfolio of solutions are pursued at the same time across and within individual firms. While adoption of incremental end-of-pipe technologies reinforces dependence on the fossil fuel energy system, a parallel engagement and experimentation with alternative energy solutions indicates that incumbent firms can also adopt a central role in niche development activities.