Sewage sludge as cheap alternative to microalgae as feedstock of catalytic hydrothermal liquefaction processes

Abstract Production of biocrude through hydrothermal liquefaction (HTL) of sewage sludge (SS) and Chlorella vulgaris was investigated. NiMo/Al2O3 (KF 851), CoMo/Al2O3 (KF 1022) and activated carbon felt, tested as catalysts at 598 K for 30 min, did not change the biocrude yield but significantly improved its quality. Quantitative sulfur removal and lower oxygen content were found in biocrude when KF 851 and KF 1022 were used with C. vulgaris. The same catalysts decreased O/C and S/C ratio of the biocrude from SS. The highest HHV (38.19 MJ/kg) and H/C ratio (1.65) and the lowest O/C (0.11) of the biocrude from SS were obtained with the cheaper activated carbon felt. A new product phase, prob…