Carbon distribution of algae-based alternative aviation fuel obtained by different pathways

Algae are considered to be the most viable feedstock for alternative aviation fuel production. The alternative (nonpetroleum) fuel from biomass could be produced as “drop-in” fuels with no effects on flight safety and would be interchangeable with current fuels in performance and handling. Accordingly, alternative fuels blended with petroleum fuels should meet jet fuel׳s requirements as laid out in the specifications (ASTM D7566). The current jet fuel specifications have implicitly limited jet fuel hydrocarbons with carbon numbers owing to the meeting of suitable physical properties. Accordingly, the carbon distribution of lipids in algae influences the aviation fuel yield and the use of biorefining pathway. This paper investigates the carbon distributions of lipids in different types of algae and characteristics of jet fuels derived from algae have also been discussed by four pathways including Fischer-Tropsch (FT) jet fuel process, hydrotreated renewable jet fuel process, pyrolysis-hydrotreated renewable jet fuel process and hydrothermal liquefaction-hydrotreated renewable jet fuel process. Moreover, carbon distributions of microalgae lipids in 103 species from 10 phyla have been concluded in order to obtain the more potential candidates for sustainable resources of bio-kerosene. The carbon distribution of a typical FT jet fuel can be modeled by the Anderson-Schultz-Flory distribution, which content can be produced to be similar to that kerosene by optimizing the FT process. The hydrotreated renewable jet fuel contains a complex carbon distribution between C7 and C18 due to the hydrotreating reactions applied, including hydrodeoxygenation, hydrocarbonylation, and decarboxylation. Pyrolysis biocrude is similar to hydrothermal liquefaction biocrude as regards carbon distribution. In pyrolysis-hydrotreated renewable jet fuel process, higher pyrolysis temperature and catalyst seem to be helpful to production of C8-C16 compounds in biofuels. In hydrothermal liquefaction-hydrotreated renewable jet fuel process, the carbon distribution of jet fuel is similar to that of pyrolysis-derived jet fuel and it lead to higher bio-kerosene product.