Valorizing manure waste into green coal-like hydrochar: Parameters study, physicochemical characteristics, combustion behaviors and kinetics

This work proposed an effective route from cow manure to coal-like hydrochar via hydrothermal carbonization (HTC). The effects of reaction conditions on product yields, physicochemical characteristics, and combustion performance of hydrochar were investigated. Both the increase of reaction temperature and reaction time resulted in the decrease of hydrochar yield but the increase of hydrochar quality, due to the strong dehydration and decarboxylation reactions occurring during HTC process. Particularly, HC-300-60 with a high HHV at 23.61 MJ/kg and high fuel ratio at 1.02, exhibited the comparable fuel quality with bituminous coal. Additionally, combustion behaviors and kinetics of hydrochars were tested by TG-DSC analysis. The hydrochar combustion process was more stable and moderate, with the minimum S index of 1.96 × 10−7%2/(°C3·min2) and the high activation energy of 50.40 kJ/mol. Simply put, this study indicates a green and promising route to valorize cow manure into high-quality solid fuel.