Hydrothermal carbonization is an attractive thermochemical method for upgrading organic waste and biomass. Hydrothermal carbonization's improvement of the upgrading and dewatering of fuel mixed with sewage sludge and low rank coal as peat was evaluated at temperatures ranging from 200 to 350 degrees C and at 60 min reaction time. The moisture content of mixed fuel (50:50 wt %) of sludge: peat was approximately 80.7%. Hydrothermal carbonization can improve sludge with a high moisture content as well as the mixed fuels increasing the latter's calorific value by reducing the hydrogen and oxygen contents of the solid products. Therefore, after the hydrothermal carbonization, the aromatic WC and O/C ratios decreased due to of the chemical conversion. These results show that the hydrothermal carbonization process can be advantageous for improving the properties of mixed fuel to reusing and upgrading sludge and low rank coal. Upgraded fuel mixed with sewage sludge and peat is characteristically resistant to change in the carbon-functional groups, and their properties as determined via Fourier transform infrared (FTIR) spectroscopy, are discussed herein. (C) 2017 Elsevier Ltd. All rights reserved.