This study investigates oxidative and non-oxidative hydrothermal processing of cellulose at five different temperatures (180-260 degrees C). Volatile fatty acids (VFAs) concentration, total suspended solid (TSS) degradation, dissolved organic carbon (DOC) and chemical oxygen demand (COD) were measured and compared in both processes. Moreover, the existence of hydrogen peroxide in both oxidative and nonoxidative processes was confirmed experimentally for the first time in literature. At temperatures 6220 degrees C the amount of H2O2 produced in the oxidative process was higher (50 fold) than that of in the non-oxidative while at higher temperatures (P240 degrees C) it was more for non-oxidative (3.5-5 fold). The concentration of VFAs in the non-oxidative process was lower than 10% of that in oxidative process. In both processes soluble COD increased with time and temperature, however at 260 degrees C after reaching a maximum, it decreased with time due to conversion of some soluble intermediates to CO2 and water. (C) 2016 Elsevier Ltd. All rights reserved.