Direct liquefaction of Dunaliella tertiolecta for bio-oil in sub/supercritical ethanol-water

► Bio-oil was produced by liquefaction of Dunaliella tertiolecta in sub/supercritical ethanol-water. ► The ethanol and water showed synergistic effects on the direct liquefaction of D. tertiolecta. ► XPS and SEM were used to verify the liquefaction behavior of D. tertiolecta and its solid residue. ► A plausible reaction mechanism of the main chemical component in D. tertiolecta is proposed. ► The optimal D. tertiolecta conversion was 98.24%, with a maximum bio-oil yield of 64.68%.