Hydrothermal gasification of Scenedesmus obliquus and its derivatives: a thermodynamic study using Aspen Plus

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AbstractThis study presents the simulation of hydrothermal gasification (HTG) of Scenedesmus obliquus microalgae and their derivatives using Aspen Plus V11. The effect of operating parameters such as temperature, pressure, and biomass concentration on the yield and composition of gaseous products using whole algae, lipid, and lipid extracted algae (LEA) as feedstocks was examined. The results showed that reaction pressure exhibited minimal impact whereas temperature, biomass concentration, and feedstock composition had significant effects on the composition of gaseous products. It was also found that a low temperature (400 °C) and biomass concentration of 40 wt% favored the production of methane‐rich gas. In contrast, high temperature (700 °C) and low biomass concentration (10 wt%) favored hydrogen‐rich gas production in all the three feedstocks considered. The highest mole fraction achieved for CH4 was 53.45, 61.70, and 52.20 mol%, which corresponded to a CH4 yield of 31.14, 56.90, and 30.15 mmol g−1 for whole algae, lipid, and LEA respectively. For H2 rich gas production, the highest mole fractions achieved were 55.77, 52.29, and 55.34 mol%, which correspond to H2 yields of 75.44, 105.51, and 73.49 mmol g−1 for whole algae, lipids, and LEA, respectively. The ranking order for the yield and lower heating value of the product gas from the HTG process is lipid > whole algae > LEA. This study has shown that hydrogen‐rich and methane‐rich gas can be produced from the hydrothermal gasification of microalgae as a function of the reaction conditions and feedstock composition. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd