Hydrothermal liquefaction of Galdieria sulphuraria grown on municipal wastewater

Two strains of Galdieria sulphuraria algae, 5587.1 and SOOS, were grown on municipal wastewater to develop energy-positive treatment systems. Hydrothermal liquefaction (HTL) of 5-10 wt% algal biomass solids was conducted at 310-350 degrees C for 5-60 min to produce bio-crude oil. HTL product yields and energy recovery were compared to those from previous studies using G. sulphuraria grown on a modified Cyanidium medium. Total bio-crude oil yields were lower (11.2-23.0 wt%) and char yields were higher (22.6-36.4 wt%) for HTL of algae grown on actual wastewater compared with that grown on media (31.4 wt% and 4.8 wt%, respectively), indicating a potential limitation for using yields from media-based studies. High-resolution mass spectroscopy of bio-crude oil provides new insights into differences in composition based on growth media. Energy recovery in total bio-crude oil and char at 350 degrees C was 17-28% and 14-19%, respectively, for the 5587.1 strain, and 23-27% and 14-25%, respectively, for the SOOS strain.