A review of bio-oil production from hydrothermal liquefaction of algae

Algae is generally regarded as the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels. Hydrothermal liquefaction is the method of dissolving organic compounds in subcritical water at high ion product, which can accelerate the acid-catalyzed and hydrolytic decomposition of algal macromolecules. This promising process converts different algal strains with high moisture content to high bio-oil yields with lower coke and lower energy consumption in comparison to other methods. The properties of the resulting bio-oil are clearly affected by parameters such as temperature, reaction time, algae species, algae concentration, reaction atmosphere, and catalysts, in subcritical water reaction conditions. This paper will provide an extensive review of the updated results on the hydrothermal liquefaction of microalgae. Including summary on the conversion of major compounds in microalgae and products related to the process and the influences of reaction conditions, catalysts and hydrotreating with comparing the variation tendencies and main results reported.