EUBCE 2026 - María JIMÉNEZ - Comparative Evaluation of Hydrothermal Liquefaction of Sewage Sludge: Influence of Feedstock Type and Reaction Conditions on Product Distribution and Integrated Valorization Potential

Comparative Evaluation of Hydrothermal Liquefaction of Sewage Sludge: Influence of Feedstock Type and Reaction Conditions on Product Distribution and Integrated Valorization Potential

Short Introductive summary

The sustainable management of sewage sludge requires efficient strategies to recover both energy and nutrients. Hydrothermal liquefaction (HTL) provides a promising route for converting wet sludge into valuable solid and liquid products under subcritical water conditions. In this study, different sludge types (primary, secondary, mixed and anaerobically digested) were characterized and processed through HTL to assess their potential for integrated valorization. Primary, secondary, and mixed sludges showed higher organic content (VS/TS ˜ 80%), while digested sludges were more mineralized (VS/TS = 55–70%) but still protein-rich (30–45% TS). COD values decreased with stabilization, indicating reduced biodegradability in digested samples. HTL reactions conducted at 150–250 °C for 10–40 min revealed that increasing reaction severity enhanced the aqueous fraction (HTL-Aq) yield while reducing solids. Secondary sludge produced the highest HTL-Aq yields (14–44 wt%), whereas digested sludges generated more stable hydrochars (45–50 wt%), demonstrating the potential of HTL for dual sludge valorization through anaerobic digestion and fertilizer applications.

M. Jiménez Corrochano, Universidad Rey Juan Carlos, Móstoles, SPAIN
G. Vicente Crespo, Universidad Rey Juan Carlos, Móstoles, SPAIN
L.F. Bautista Santa Cruz, Universidad Rey Juan Carlos, Móstoles, SPAIN
J. L. Molto Marin, Tedagua, Madrid, SPAIN
R. Fernández Donado, Tedagua, Madrid, SPAIN
M.P. Sánchez Miranda, Tedagua, Madrid, SPAIN