Solvent-free lipid extraction from microalgal biomass with subcritical water in a continuous flow reactor for acid-catalyzed biodiesel production

•Subcritical treatment employed for solvent-free lipid extraction from wet microalgae.•Lipid recovery of 72.3% and FAME content of 44% was achieved without using solvent.•Lipid content was increased from 2.19% to 44% compared with the original wet biomass.•Subcritical water dissolve carbohydrate and separate lipid from biomass by filtering.•Esterification efficiency of lipid separated through subcritical treatment reached 98.4%.