Hydrothermal liquefaction of Spirulina and Nannochloropsis salina under subcritical and supercritical water conditions

Six hydrothermal liquefaction experiments on Nannochloropsis salina and Spirulina platensis at subcritical and supercritical water conditions (220-375 degrees C, 20-255 bar) were carried out to explore the feasibility of extracting lipids from wet algae, preserving nutrients in lipid-extracted algae solid residue, and recycling process water for algae cultivation. GC-MS, elemental analyzer, FT-IR, calorimeter and nutrient analysis were used to analyze bio-crude, lipid-extracted algae and water samples produced in the hydrothermal liquefaction process. The highest bio-crude yield of 46% was obtained on N. sauna at 350 degrees C and 175 bar. For S. platensis algae sample, the optimal hydrothermal liquefaction condition appears to be at 310 degrees C and 115 bar, while the optimal condition for N. sauna is at 350 degrees C and 175 bar. Preliminary data also indicate that a lipid-extracted algae solid residue sample obtained in the hydrothermal liquefaction process contains a high level of proteins. (C) 2013 Elsevier Ltd. All rights reserved.