Qualitative improvement of bio-oil derived from hydrothermal liquefaction of liquid fertiliser drained Kappaphycus alvarezii

The purpose of this investigation was to explore the possibility of utilising post-sap residues for bio-oil production, that are produced after liquid fertiliser extraction from Kappaphucus alverizii, red macroalgae. The sap - a liquid fertiliser - was expelled by crushing the K. alverizii. The residual macroalgae were hydrothermally liquified at varying operating conditions (temperature, biomass to solvent ratio, residence time, catalyst dose), in order to understand its influence over the productdistribution and composition from thehydrothermal liquefaction (HTL) process. The maximal yield for crude bio-oil was 28.4 +/- 0.6 wt.%, which was possible only when the HTL reactor was operated in presence of a ZSM-5 catalyst at 300 degrees C using 20 g of biomass for 30 min duration. Still, the bio-oil derived from the HTL process seems to possess higher oxygen content. Hence, the hydro-deoxygenation (HDO) process was carried out to upgrade the crude bio-oil into oxygenates less oil. The bio-char along with ZSM-5 derived from the previous HTL process was utilised as a catalyst in the HDO process. Catalysed HDO processes were able to improve the HHV of upgraded oil to 36.7 MJ/kg. Overall, this study implies that the crude bio-oil can be effectively produced from the post-sap residue, which can be further upgraded to calorific-rich fuel.

Automated summary

The purpose of this investigation was to explore the possibility of using post-sap residues from red macroalgae for bio-oil production. The residues were hydrothermally liquefied under different conditions, and the influence of these conditions on the product distribution and composition was analyzed. The crude bio-oil yield reached its maximum of 28.4 +/- 0.6 wt.% when the process was carried out at 300 degrees C for 30 minutes with the presence of a ZSM-5 catalyst. To reduce the oxygen content in the bio-oil, hydro-deoxygenation (HDO) process was conducted with the utilization of bio-char and ZSM-5 as catalysts. The study suggests that crude bio-oil can be effectively produced from post-sap residues and further upgraded into high-calorific fuel.