A detailed kinetic model for the hydrothermal decomposition (HTD) of sewage sludge was developed based on an explicit reaction scheme considering exact intermediates including protein, saccharide, NH4+-N and acetic acid. The parameters were estimated by a series of kinetic data at a temperature range of 180-300 degrees C. This modeling framework is capable of revealing stoichiometric relationships between different components by determining the conversion coefficients and identifying the reaction behaviors by determining rate constants and activation energies. The modeling work shows that protein and saccharide are the primary intermediates in the initial stage of HTD resulting from the fast reduction of biomass. The oxidation processes of macromolecular products to acetic acid are highly dependent on reaction temperature and dramatically restrained when temperature is below 220 degrees C. Overall, this detailed model is meaningful for process simulation and kinetic analysis. (C) 2015 Elsevier Ltd. All rights reserved.