Chapter 2 - Biojet fuel production pathways

Abstract

Biojet fuels can be produced from a variety of feedstocks and production pathways. The hydroprocessed ester and fatty acid (HEFA) pathway using edible oils is presently the dominant production method due to the twin factors of being approved as a drop-in blend fuel by ASTM and also being the only commercially available technology. In this chapter, the production methods are broadly categorized into oil-to-jet (OTJ), alcohol-to-jet (ATJ), gas-to-jet (GTJ), and sugar-to-jet (STJ). Within them, the OTJ methods cover HEFA, catalytic hydrothermolysis (CH), and hydroprocessed depolymerized cellulosic jet (HDJC); ATJ methods comprises of ethanol-to-jet (ETJ) and butyl ATJ; GTJ contains the Fischer–Tropsch (FT) and biomass-to-fuel pathways; and STJ methods include direct sugar-to-hydrocarbon and aqueous phase reforming. The required feedstock, intermediates, processes, and operating conditions for each pathway are detailed. Improvements to existing methods are also presented with the strengths and drawbacks being discussed. While the HEFA pathway predominates the biojet fuel industry, other processes such as the FT and ETJ are rising up in the technology readiness level curve to be potentially viable in near term.