Temperature effect on hydrothermal liquefaction of Nannochloropsis gaditana and Chlorella sp.

Temperature effect on hydrothermal liquefaction (HTL) of Nannochloropsis gaditana and Chlorella sp. was investigated with 10% biomass loading at HTL temperatures of 180-330 degrees C, and reaction time of 30 min. Maximum yields of 47.5% for Nannochloropsis sp. and 32.5% biocrude oil yields for Chlorella sp. were obtained at 300 degrees C. The higher heating values of biocrude oils produced in this work ranged between 34 and 39 MJ/kg. 79% of energy in the Nannochloropsis sp. was recovered at 300 degrees C and 62% of energy recovery from Chlorella sp. was achieved at 200 degrees C. Valuable nutrients (NH3-N and PO43-) produced during the HTL process were quantified, from the aqueous phase for both strains of biomass. The aqueous phase samples obtained at all temperatures were also analyzed for amino acids and carbohydrates. The suitable temperatures for extraction of lipids, amino acids and carbohydrates have been identified. Sequential HTL experiments conducted have shown the prospect of recovering nutrients and other valuable byproducts along with biocrude oil. The experimental results and analysis indicate that sustainable biofuel production requires the development of strain based strategies for the hydrothermal liquefaction process. (C) 2016 Published by Elsevier Ltd.