Effect of algae (Scenedesmus obliquus) biomass pre-treatment on bio-oil production in hydrothermal liquefaction (HTL): Biochar and aqueous phase utilization studies

Environmental concerns due to fossil fuel usage has turned the research interest towards biomass and bioenergy field. Renewable biomass such as microalgae provides numerous advantages as they can grow in wastewater; sequester carbon dioxide, economical and eco-friendly. In this study, effect of pretreatment of microalgae (Scenedesmus obliquus) biomass using post-hydrothermal liquefaction wastewater (PHWW) for bio-oil production through hydrothermal liquefaction at a temperature of 300 degrees C was studied. Results showed liquefaction of pre-treated biomass yielded 48.53% bio-oil whereas 28.35% was resulted from bio-mass without pretreatment. The analysis of higher heating value of bio-oil showed that pretreated biomass oil has 36.19 MJ.Kg(-1) against non-pretreated biomass oil, which has 28.88 MJ.Kg(-1). Bio-oil (pretreated bio-mass) analysis revealed that 60% of compounds are in diesel and gasoline range with 58.09% of energy re-co very. Bio-oil was rich in hydrocarbons of C-7-C-21 range with less oxygenated compounds. Carbon balance showed that an increase of 13% of carbon was sequestered in solid residue obtained from pretreated biomass and about 146% of increase also obtained in bio-oil. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study demonstrates that pretreating microalgae biomass with post-hydrothermal liquefaction wastewater can increase bio-oil yield and heating value, aiding in carbon sequestration. The bio-oil from pretreated biomass is rich in hydrocarbons, mainly in the range of C-7 to C-21.