Production and thermophysico-chemical characterization of charcoal briquettes from anaerobic fermentation digestate

Abstract

Wood energy valorization dominates and accelerates deforestation with negative consequences for climate change. To reduce pressure on forests and mitigate climate change, this study proposes a sustainable solution aimed at producing ecological charcoal briquettes from digestates derived from cow dung and Titonia diversifolia. For this purpose, digestates from a 45-day mesophilic anaerobic co-digestion were dried to 8% moisture content over 35 days. The dried digestates were then submitted to uncontrolled pyrolysis. The parallelepiped and the cylindrical charcoal briquette were produced and tested. The results are as follows: the maximum pyrolysis temperature reached 390°C. The produced biochar was compressed into parallelepiped and cylindrical briquettes. Physicochemically, no difference between the two shapes was observed. Thermally, the heating value of the cylindrical and parallelepiped briquettes was 19 kJ/kg. Practically, the cylindrical shape, although less energy-efficient per unit of time, offers better heat utilization efficiency (a greater amount of water evaporated for an equivalent mass consumed), while the parallelepiped shape is characterized by higher instantaneous power, but with greater heat losses to the environment. Finally, optimizing the geometry and pressing of briquettes is essential to improving the efficiency and sustainability of biofuels, particularly in low-resource artisanal contexts.