Conversion of brewed tea waste into hydrochar and activated carbon

Feasibility of hydrochar and activated carbon production from brewed tea waste was investigated in this study. Brewed tea waste was hydrothermally carbonised in subcritical water to obtain hydrochar as energy feedstock. Hydrothermal carbonisation experiments were performed at different process temperatures to determine its effect on fuel properties and combustion behaviour of resultant hydrochar. Increasing the process temperature yielded less amount of hydrochar. Higher calorific value and lower burnout temperature was observed for hydrochar. Hydrothermal carbonisation could remove only 25%-35% of initial ash in biomass and could not remove CaO in brewed tea waste. Hence, hydrochar had high slagging risk during combustion, which was only slightly lower than that of feedstock. On the other hand, hydrochar had lower fouling risk due to removal of K2O. ZnCl2 activation of hydrochar produced an activated carbon with high surface area and acceptable porosity.