Biocrude oil production from Chlorella sp. cultivated in anaerobic digestate after UF membrane treatment

Algae cultivation in animal wastewater could recover nutrient resources, and harvest considerable amount of algae biomass for biofuel conversion. In this study, Chlorella sp. cultivated in ultrafiltration (UF) membrane treated anaerobic digestion effluent of chicken manure was converted into biocrude oil through hydrothermal liquefaction (HTL). The potential of biocrude production from grown Chlorella sp. was studied through changing the operational conditions of HTL, i.e., holding temperature (HT, 250°C-330°C), retention time (RT, 0.5-1.5 h), and total solid (TS) (15 wt%-25 wt%) of the feedstock. The highest biocrude oil yield was 32.9% at 330°C, 1.5 h and 20 wt% TS. The single factor experiments of HT also suggested that the biocrude oil yield decreased when the temperature was higher than 330°C. There were no significant differences of elemental contents in biocrude samples. The maximum higher heating values (HHV) of Chlorella sp. biocrude was 40.04 MJ/kg at HT of 330°C, RT of 1 h and TS of 15 wt%. This study suggests the great potential for energy recovery from Chlorella sp. cultivated in UF membrane treated anaerobic digestion effluent via HTL.