Bio-jet fuels from photosynthetic microorganisms: A focus on downstream processes

The aviation industry is a "hard to electrify" sector with limited possibilities for alternative fuels such as green hydrogen. Therefore, there is a call for sustainable fuel alternatives which is driving intensive research into bio- jet fuels (BJF) that could be used in aviation, without revamping the aircraft fleets and the aviation infrastructures. This review evaluates the potential of photosynthetic microorganisms, focusing on the most challenging downstream processes, i.e. bio-oil production and its catalytic upgrade. The main bottlenecks of such processes are identified, and the most recent solutions, offered to overcome them, are critically reviewed. Finally, a statistical analysis of the key characteristics of current BJF derived from microalgae and cyanobacteria is presented, along with a discussion on their suitability for the aviation industry and the primary areas for improvement.