ABSTRACT
The increase of air transportation assimilated a substantial role in the depletion of fossil fuel reservoirs. Considering the emissions and the environmental impact, net-zero CO2 emission-based biomass fuels are preferred over fossil fuels. Bio-aviation fuels can fulfill the essential properties of conventional aviation fuels with adaptability to current engine designs with overall cost benefits. Algal biofuels are third-generation fuels responsible for the significant photosynthetic activity with a high yield of commercial by-products. The production of algal bio-crude can be achieved by various biochemical and thermochemical processes. However, it is challenging to separate multiple higher molecular weight compounds present in algal bio-crude oil that are responsible for carbon and NOx emissions when used directly in internal combustion engines. A variety of both physical and chemical methods/technologies are available for improving algal bio-crude. The operating conditions of upgrading can range from mild conditions to high pressures and temperatures. In this study, various routes for the production of biofuels from microalgae and macroalgae were presented, emphasizing the role of feedstock in influencing the properties and extraction techniques when compared with conventional and non-conventional sources. Furthermore, the upgrading of algal bio-crude to bio-jet fuels via catalytic cracking, hydroprocessing and supercritical fluids, and their reaction mechanism were assessed.
