Assessing the future prospects of emerging technologies for shipping and aviation biofuels: A critical review

There is an urgent need to switch from fossil to bio-based fuels in the transport sector, particularly in shipping and aviation. The growth of the world's population has resulted in a significant impact on passenger transport, with a noticeable increase in greenhouse gas emissions, depletion of fossil resources and associated risks in all three pillars of sustainability. In this context, new policies, standards and targets have been developed to reduce this environmental damage, which is mainly caused by the use of fossil fuels. Therefore, the alternative of using biofuels seems to be the most appropriate solution, to the extent that important targets have been set and specific directives have been developed for the integration of biofuels in the maritime and aviation sectors. However, to demonstrate that switching to biofuels is indeed beneficial, it is necessary to evaluate new biofuel scenarios from a life-cycle perspective, with particular emphasis on analyses that provide information beyond the present, such as prospective life-cycle assessments. To this end, the focus of this review is on the current trends in the production of biofuels for the marine and aviation sectors, taking into account the main targets set, the existing regulations and directives on the subject, and an analysis of the type of technologies used for their production. It also addresses biofuel Life Cycle Assessment (LCA) scenarios and future LCA approaches, and how these analyses should be carried out to be effective. Finally, key policies, standards and certifications are analyzed. The trends and bottlenecks discussed in this review concerning the actual and future development of the biofuels sector could be used by policy makers and stakeholders to identify efforts that favor the integration of biofuels into the value chain. Furthermore, it could be concluded that the evaluation of the guidelines foreseen in the development of competitive scenarios based on emerging technologies, as well as the adoption of policies and restrictions on the use of fuels, are key conditions to establish the roadmap for the widespread implementation of biofuels.