Effect of process parameters on hydrothermal liquefaction of oil palm biomass for bio-oil production and its life cycle assessment

•Water is used as a clean solvent to liquefy palm biomass to bio-oil.•The optimum liquefaction condition of oil palm biomass is 390 °C and 25 MPa.•Optimum reaction time for liquefaction of empty fruit bunch and palm mesocarp fiber is 120 min.•Optimum reaction time for liquefaction of palm kernel shell is 240 min.•From the life cycle assessment, a net 2.29 kg CO2 equivalent is generated per kg of bio-oil produced.

This paper presents the studies on the effect of three process parameters; temperature, pressure and reaction time on the subcritical and supercritical hydrothermal liquefaction of oil palm empty fruit bunch, palm mesocarp fiber and palm kernel shell. The effect of temperature (330–390 °C), pressure (25–35 MPa) and reaction time (30–240 min) on bio-oil yields were investigated using a Inconel batch reactor. The optimum liquefaction condition for empty fruit bunch, palm mesocarp fiber and palm kernel shell was at supercritical condition of water; 390 °C and 25 MPa. For the effect of reaction time, bio-oil from empty fruit bunch and palm mesocarp fiber attained maximum yields at 120 min, whereas bio-oil yield from palm kernel shell continued to increase at reaction time of 240 min. Lastly, a life cycle assessment based on a conceptual biomass hydrothermal liquefaction process for bio-oil production was constructed and presented.