Biogas production and digestate quality evaluation of anaerobic co-digestion of Hura crepitans leaves and cow dung in a vertical plug-flow digester study

This study investigated the potential of the continuous anaerobic co-digestion (AcoD) of Hura crepitans leaves and cow dung for biogas production under mesophilic conditions in a vertical plug-flow digester. The substrates were combined in ratio 1:1, mixed with water and allowed to acclimatize for 14 days before weekly feeding at organic loading rate (OLR) of 3.79 gVS/L d. AcoD was performed for a retention time of 7 weeks (49 days). Physicochemical analysis revealed Hura crepitans leaves had a high total solid (TS) content of 96% and volatile solid (VS) content of 83.85% while cow dung exhibited a TS of 26% and VS of 17.49%. The carbon-to-nitrogen (C/N) ratios of Hura crepitans and cow dung were 17.75 and 141.19 respectively Weekly biogas production measurements demonstrated a diauxic growth pattern, with initial production at 4.32 L in week 1, followed by a notable increase to 6.48 L in week 2, a significant drop to 1.40 L in week 3, and a recovery to higher production in weeks 4 through 7, culminating in a cumulative biogas production of 30.77 L at the end of the AD process. The biofertiliser potential of the digestate was evaluated, and the results indicated its potentials for agricultural purposes. The findings of this study suggest that the co-digestion of Hura crepitans leaves and cow dung in a vertical plug-flow digester could improve biogas production and promote sustainable waste management.