Co-liquefaction of microalgae and lignocellulosic biomass in subcritical water

This study investigated co-liquefaction of microalgae (Chlorella pyrenoidosa, CP) and lignocellulosic biomass (Rice husk, RH) in subcritical water for bio-oil production. The effects of liquefaction temperature (200-350 °C), residence time (10-90 min), solid concentration (10-30 wt.%) and mass ratio of CP/RH on product distribution were investigated. The results showed that the highest yield of bio-crude oils at the combination of 50% CP with 50% RH was obtained at 300 °C temperature, 60 min residence time and 20 wt.% solid concentration. The oil yields increased gradually with the increased mass ratio of CP/RH. The major compounds identified in bio-crude oils from hydrothermal liquefaction (HTL) of RH were cyclic oxygenates (20.62%), followed by esters, ketones and alcohols (17.19%). As for CP, the main components were straight & branched amides (28.38%). A synergistic interaction was observed between CP and RH during co-liquefaction, resulting in decreased acidity and nitrogen content of bio-crude oils.