From the Cultivation of Arthrospira platensis at an Increased CO2 Concentration to the Bio-Oil Production by Hydrothermal Liquefaction

In this work, the path from the cultivation of Arthrospira platensis at an increased concentration of CO2 to the production of bio-oil by hydrothermal liquefaction (HTL) of the grown biomass is realized. The cultivation was carried out in a 90 L photobioreactor at an initial CO2 concentration of 8 vol.% for 15 days. During the cultivation stage, the optical density for microalgae suspension, pH and chemical composition of nutrient medium were monitored. The grown biomass was separated from the nutrient medium with a 100 µm mesh and then subjected to HTL at 330 °C for 1 h. The biomass growth rate was 82 ± 4.1 mg × L−1day−1 and the pH was in the range from 9.08 ± 0.22 to 8.9 ± 0.24. Biochemical and CHNS analyses were applied for the obtained biomass. The contents of carbohydrates, proteins and lipids in the grown biomass were 38.7 ± 0.4 wt.%, 37.4 ± 0.5 wt.% and 3.8 ± 0.4 wt.%, respectively. Bio-oil yield after the HTL procedure was 13.8 wt.%. The bio-oil composition and properties were determined by GH-MS, TLC-PID and ICP-MS techniques. ICP-MS revealed the contents of 51 metals in bio-oil.