In this study, hydrothermal carbonization was used to upgrade waste biomass at temperatures ranging from 150 to 375 oC and a residence time of 30 minutes. The kinetics of hydrothermal carbonization was investigated and fuel properties of produced hydrochars were evaluated. The kinetic study indicated that hydrothermal carbonization of biomass followed first-order reaction rate with the apparent activation energy of 67.41 and 179.54 kJ/mol for coconut fiber and 59.18 and 173.70 kJ/mol for eucalyptus leaves within the temperature ranges of 150-300 oC and 300-375 oC, respectively. Hydrothermal carbonization narrowed the differences in fuel properties among different biomass feedstocks. The fuel qualities of hydrochars were significantly improved: increased ignition temperatures and elevated combustion temperature regions compared to raw biomass feedstock. The present study showed that hydrothermal carbonization was a promising conversion process for the production of the hydrochars which had increased fuel qualities compared to raw biomass.