Hydrothermal carbonization of waste from leather processing and feasibility of produced hydrochar as an alternative solid fuel

Abstract This study presents hydrothermal carbonization (HTC) of leather waste (LW) to produce hydrochar and feasibility of using produced hydrochar as solid fuel. The results showed that a relatively low HTC treatment temperature (180–200 °C) improved both the hydrochar product yield (>82.9% by dry weight) and its potential use as a solid fuel with in terms of its physicochemical properties and heating value. Furthermore, the hydrochar showed a higher heating value (5807–6508 kcal kg −1 ) compared to that of low-ranked coals ( i.e., sub-bituminous and lignite), and stable combustion characteristics at a higher temperature. This allows the hydrochar to be considered as a suitable alternative to conventional fossil fuel. In addition, the decrease of nitrogen content in the hydrochar during the HTC treatment, and the inherent low sulfur content of LW could make hydrochar a more appealing clean energy source. The findings of this study suggest that the conversion of LW through HTC can be a useful method for waste management and energy recovery from abandoned biomass.