Catalytic hydrothermal co-liquefaction of sewage sludge and agricultural biomass for promoting advanced biocrude production

Conventional hydrothermal liquefaction (HTL) technology is inhibited by the complicated feedstock properties, low biocrude yield, and poor biocrude quality. Herein, this work aimed to propose a novel catalytic hydrothermal co-liquefaction (catalytic co-HTL) route for enhancing high-quality biocrude production. Four representative biowastes were applied to determine the synergistic effects in co-HTL treatment. Binary sewage sludge (SS)/wheat straw (WS) presented the highest synergistic effect (14.05%) on biocrude production. Furthermore, homogenous and heterogeneous catalysts (i.e., Na2CO3, HY, SSB, CSB, and Ni@CSB) were comprehensively tested during catalytic co-HTL of binary SS/WS. Biocrude produced over Ni@CSB revealed the highest carbon content at 75.5% and HHV at 36.96 MJ/kg, due to the deoxygenation and desulfurization reactions enhanced by Ni@CSB. Thermalgravimetric behaviors and kinetic studies of biocrude degradation were further analyzed. Moreover, the byproducts (hydrochar and gaseous phase) were characterized. Overall, this study provides an effective and promising route to valorize biowastes into green high-quality biocrude.