Bio-oil production by catalytic solvent liquefaction from a wild microalgae consortium

Due to the increase in greenhouse gas emissions by combustion of fossil fuels, new alternatives for obtaining clean energy have been investigated. In this work, a wild microalgae consortium, grown in treated wastewater, was used to produce bio-oil by catalytic solvent liquefaction process. Tetralin and zeolite HZSM-5 (Si/Al = 80) were employed as a reaction medium and catalyst, respectively. The effect of H2 pressure and reaction time on biocrude yield, conversion of biomolecules, and the type of generated chemical compounds in the bio-oil were investigated, and reaction schemes were proposed. The best reaction condition was at 120 min and 760 psi, where a bio-oil yield of 51 wt% was obtained and high percentage of the original protein content was converted. The main type of compounds in the produced bio-oil were oxygenated (~ 50 chromatographic area %) and nitrogenated (~ 18 area %) compounds. H2 pressure is an important variable to process proteins, lipids, and simple carbohydrates. Despite the high protein content in the feedstock, a relatively low nitrogen content of 1.2–1.5 wt% was found in the resultant bio-oil, which has an estimated HHV of 32–33 MJ/kg.