Pretreatment of cyanobacterial Chroococcidiopsis. biomass prior to hydrothermal liquefaction for enhanced hydrocarbon yield and energy recovery

Abstract

Chroococcidiopsis sp. was grown in 200 L open raceway pond. Biomass density and average biomass productivity were 0.41 g/L and 16.1 g/m2/d. Chroococcidiopsis biomass was harvested by self-settling. Self settled biomass was further subjected to centrifugation to obtain a biomass paste with 25-30% solid content. Centrifuged biomass was dried at 80 °C overnight and used as a feedstock for pretreatment step. Biomass was pretreated in water at 105 °C for 15 minutes. A slurry containing 15 wt% pretreated and untreated biomass (control) in deionized water was prepared and subjected to hydrothermal liquefaction for biocrude oil production. Hydrothermal liquefaction for both pretreated and untreated biomass was conducted at temperatures ranging from (275, 300, 325, 350 °C) in a 500 mL high pressure PARR reactor for 30-minute reaction holding time. Maximum biocrude yields for pretreated and untreated biomass was 42.4 % and 26.4 % based on ash free dry weight basis. Biocrude oil was characterized for hydrocarbons using GC-MS technique. Biocrude oil obtained from pretreated and untreated biomass contained 58.9% and 41.01% (C8-C19) hydrocarbons. Higher heating values for biomass and biocrude oil were 16.93 and 31.28 MJ/kg, with an energy recovery value of 41.1%.