Effects of processing conditions on biocrude yields from fast hydrothermal liquefaction of microalgae

This study investigated the effects of algae species, reaction time, and reactor loading on the biocrude yield from fast hydrothermal liquefaction (HTL) of microalgae. Fast HTL reaction times were always less than 2 min and employed rapid heating and nonisothermal conditions. The highest biocrude yield obtained was 67 ± 5 wt.% (dry basis). With all other process variables fixed, increasing the reaction time in a 600 °C sand bath by 15 s increments led to a rapid increase in biocrude yield between 15 and 45 s. At longer times, the biocrude yield decreased. Low reactor loadings generally gave higher biocrude yields than did higher loadings. The low reactor loadings may facilitate biocrude production by facilitating cell rupture and/or increasing the effective concentration of algal cells in the hot, compressed water in the reactor.