Influence of biochemical composition during hydrothermal liquefaction of algae on product yields and fuel properties

Hydrothermal liquefaction (HTL) of nine algae species were performed at two reaction temperatures (280 and 320 °C) to compare the effect of their biomass composition on product yields and properties. Results obtained after HTL indicate large variations in terms of bio-oil yields and its properties. The maximum bio-oil yield (66 wt%) was obtained at 320 °C with a high lipid containing algae Nannochloropsis. The higher heating value of bio-oils ranged from 31 to 36 MJ/kg and around 50% of the bio-oils was in the vacuum gas oil range while high lipid containing algae Nannochloropsis contained a significant portion (33–42%) in the diesel range. A predictive relationship between bio-oil yields and biochemical compositions was developed and showed a broad agreement between predictive and experimental yields. The aqueous phases obtained had high amount of TOC (12–43 g/L), COD (35–160 g/L), TN (1–18 g/L), ammonium (0.34–12 g/L) and phosphate (0.7–12 g/L).