Improvement in bio-crude yield and quality through co-liquefaction of algal biomass and sawdust in ethanol-water mixed solvent and recycling of the aqueous by-product as a reaction medium

Co-liquefaction of algal biomass (AB) and sawdust (SD) was investigated in ethanol-water mixed solvent for the production of bio-crude. Effects of temperature (200–300 °C), residence time (30–120 min), ethanol-water mixed solvent composition (0/100–100/0 wt/wt), and AB/SD mass ratio (0/100–100/0) on the products distribution were explored. The results indicated that both AB/SD and ethanol/water exhibited positive synergistic effects on the co-liquefaction process. The highest bio-crude yield of 58 wt% was obtained from co-liquefaction of AB and SD (50/50, wt/wt) in ethanol-water (75/25, wt/wt) mixed solvent at 250 °C for 60 min. In addition, the bio-crude produced from the mixed feedstocks contained a higher fraction of light oil components than that produced from only AB or SD. In addition, this work demonstrated the promise of recycling the aqueous by-product form the co-liquefaction process as a reaction medium for the process, aiming to reduce overall waste generation and increase the bio-crude quality.