The biomass of halophytic microalga Tetraselmis sp. with 16% w/w solids was converted into biocrude by a hydrothermal liquefaction (HTL) process in a batch reactor at different temperatures (310, 330, 350 and 370 degrees C) and reaction times (5, 15, 30, 45 and 60 min). The biocrude yield, elemental composition, energy density and severity parameter obtained at various reaction conditions were used to predict the optimum condition for maximum recovery of biocrude with improved quality. This study clearly indicated that the operating condition for obtaining maximum biocrude yield and ideal quality biocrude for refining were different. A maximum biocrude yield of similar to 65 wt% ash free dry weight (AFDW) was obtained at 350 degrees C and 5 min, with a severity parameter and energy density of 5.21 and similar to 35 MJ/kg, respectively. The treatment with 45 min reaction time recorded similar to 62 wt% (AFDW) yield of biocrude with and energy density of similar to 39 MJ/kg and higher severity parameter of 7.53. (C) 2014 Elsevier Ltd. All rights reserved.