Effect of operating conditions of thermochemical liquefaction on biocrude production from Spirulina platensis

This study investigated the optimum thermochemical liquefaction (TCL) operating conditions for producing biocrude from Spirulina platensis. TCL experiments were performed at various temperatures (200–380 °C), holding times (0–120 min), and solids concentrations (10–50%). TCL conversion at 350 °C, 60 min holding time and 20% solids concentration produced the highest biocrude yield of 39.9% representing 98.3% carbon conversion efficiency. Light fraction biocrude (B1) appeared at 300 °C or higher temperatures and represented 50–63% of the total biocrude. Biocrude obtained at 350–380 °C had similar fuel properties to that of petroleum crude with energy density of 34.7–39.9 MJ kg−1 compared to 42.9 MJ kg−1 for petroleum crude. Biocrude from conversion at 300 °C or above had 71–77% elemental carbon, and 0.6–11.6% elemental oxygen and viscosities in the range 40–68 cP. GC/MS of biocrude reported higher hydrocarbons (C16–C17), phenolics, carboxylic acids, esters, aldehydes, amines, and amides.

Research highlights
► Optimum liquefaction conditions were 350 °C temperature, 60 min time, 20% solids.
► Biocrude yield at optimum thermochemical liquefaction (TCL) was 39.9%.
► Carbon conversion efficiency for most TCL runs were >93%.
► Biocrudes obtained at 350–380 °C had fuel properties close to the petroleum crude.