Thermochemical conversion is a promising route for recovering energy from algal biomass. Two thermochemical processes, hydrothermal liquefaction (HTL: 300 °C and 10-12. MPa) and slow pyrolysis (heated to 450 °C at a rate of 50 °C/min), were used to produce bio-oils from Scenedesmus (raw and defatted) and Spirulina biomass that were compared against Illinois shale oil. Although both thermochemical conversion routes produced energy dense bio-oil (35-37. MJ/kg) that approached shale oil (41. MJ/kg), bio-oil yields (24-45%) and physico-chemical characteristics were highly influenced by conversion route and feedstock selection. Sharp differences were observed in the mean bio-oil molecular weight (pyrolysis 280-360. Da; HTL 700-1330. Da) and the percentage of low boiling compounds (bp < 400 °C) (pyrolysis 62-66%; HTL 45-54%). Analysis of the energy consumption ratio (ECR) also revealed that for wet algal biomass (80% moisture content), HTL is more favorable (ECR 0.44-0.63) than pyrolysis (ECR 0.92-1.24) due to required water volatilization in the latter technique.
- Hydrothermal liquefaction
ASJC Scopus subject areas
- Environmental Engineering
- Renewable Energy, Sustainability and the Environment
- Waste Management and Disposal