Physicochemical, structural and combustion analyses to estimate the solid fuel efficacy of hydrochar developed by co-hydrothermal carbonization of food and municipal wastes

The application of a char derived from fruit peel waste and other municipal wastes as solid fuel depends on its physico-chemical properties. In this work, fruit peel waste (FW) along their mixture with facial tissue waste (FT) and wrapping paper waste (WP) as well as their respective hydrochars (FWHC, FTHC, and WPHC) produced via hydrothermal carbonization (HTC) was characterized in detail to ascertain their applicability as solid fuel. Moreover, the elemental O contents for FTHC and WPHC were about 12.8 and 5.1% respectively higher than FWHC. Heating value analysis indicated that WPHC had the highest HHV of 5164 kcal/kg. Combustion kinetic studies, carried out by thermogravimetric technique, revealed that about 33.78 kJ/mol of energy was required to generate a combustion reaction for WP, higher than the energy required to ignite WPHC (28.2 kJ/mol). The regression coefficient (R2) values were higher than 0.94, indicating that the Arrhenius equation could be used to model the sample combustion process. Overall, the study showed that Co-HTC of FW with paper-based municipal waste such FT and WP is an effective method of converting FW to a cleaner hydrochar (HC) with high calorific value and less sulphur content.