Production of light oil-prone biocrude through co-hydrothermal liquefaction of wastewater-grown microalgae and peat

Bioenergy production from biomass through thermochemical conversion is an emerging technological advancement that can offset the use of fossil fuels and reduce greenhouse gas (GHGs) emissions. This study investigated novel co-hydrothermal liquefaction (co-HTL) using peat (P) and wastewater-grown microalgae (MA) for enhancing biocrude production as waste to energy approach. The operating conditions were: temperature 300 C, biomass loading-10 mL, and reaction time-60 min. The improvement of biocrude yield was investigated using three co-HTL ratios of P and MA (75:25, 50:50, 25:75) and compared with two individual biomass HTL. Between individual HTL of P and MA sample, MA sample yielded higher biocrude (31 wt%) than P sample (26 wt %). In addition, the highest higher heating value (HHV) of 35.8 MJ/kg and energy recovery of 59.8% were observed for individual HTL of the MA sample. However, the highest biocrude yield (36.6 wt%) was observed for co-HTL of 50:50 ratios with a biomass conversion rate of 54.7 wt% and HHV of 32 MJ/kg. Fourier-transform infrared (FTIR) spectroscopy detected alcohol, phenolic, and ester compounds in the biocrude samples. All of the biocrude samples were mainly premature quality with kerogen type I (highly oil-prone). The co-HTL biocrude samples exhibited heavy to medium type oil based on American Petroleum Institute (API) gravity analysis. The elemental analysis showed that the H/C ratio of biocrude samples was within 1.5-2.0, similar to Petro-crude quality. Gas chromatography flame ionization detection (GC-FID) analysis confirmed that the co-HTL biocrude had higher lighter fraction oil than HTL. Energy balance analysis revealed that the system was energetically feasible, and net energy gain significantly improved during co-HTL. The overall assessment summarized that a positive synergistic effect was achieved during co-HTL of P and MA on the improvement of the biocrude yield and quality.

Automated summary

Bioenergy production from thermochemical conversion of biomass using co-hydrothermal liquefaction of peat and wastewater-grown microalgae was studied. The highest biocrude yield was achieved with a 50:50 ratio of peat and microalgae, and the biocrude exhibited similar properties to petroleum. Energy balance analysis showed the system to be energetically feasible, with significant improvement in net energy gain during co-hydrothermal liquefaction.