Hydrothermal conversion of anaerobic wastewater fed microalgae: effects of reaction temperature on products distribution and biocrude properties

Abstract

Microalgae using non-arable land were considered as promising biomass for biocrude production through hydrothermal liquefaction (HTL) and can also be used for environmentally-friendly wastewater treatment. In this study, we illuminated the effect of reaction temperature on the products distribution and biocrude properties from HTL of the Chlorella sp. grown in wastewater from anaerobic digestion (AD) of chicken manure via HTL. The highest biocrude yield (30.35%, daf) and energy recovery rate (49.6%) were both achieved at 330 °C, while the highest HHV (37.17 MJ/kg) of biocrude oil was achieved at 290 °C. The biocrude oil yield increased from 25.46 to 30.35% as the temperature increased from 270 to 330 °C. The gases yield showed a similar trend under 310 °C. On the contrary, the solid products yield decreased as the temperature approached 350 °C. The lowest nitrogen content (4.6%) and highest H/C (1.50) of biocrude oil were obtained at 290 and 270 °C, respectively. Results imply that deoxygenation was enhanced with temperature due to the enhanced decarboxylation at higher temperatures. Specially, the nitrogen content decreased by 39.4-47.4% in the temperature range of 270-350 °C. The integrated pathways for energy production and nutrient recycling from animal manure coupling AD/HTL, and algae technologies were further proposed.

Biocrude Production from Hydrothermal Liquefaction of Chlorella: Thermodynamic Modelling and Reactor Design

“…Temperature significantly influences the HTL fraction products and determines the reaction pressure, which is generally regarded as the most important factor for HTL of biomass [5]. Table 2 summarizes the properties of Chlorella and the corresponding experimental biocrude yields in literature [27][28][29][30][31]. Experimental biocrude yields ranged from 26 wt% to 63.4 wt% due to differences in the properties of Chlorella, especially the lipid contents.…”