Anaerobic digestion of organic waste, such as cow dung, offers a sustainable solution for waste management and renewable energy production. In this study, four bioreactors were constructed using 25 L capacity gallons, with three containing cow dung mixed with each powder (50 g) of Azadirachta indica (neem), Curcuma longa (turmeric) and Carica papaya (papaya) and designated as CDNP (cow dung mixed with neem powders); CDTP (cow dung mixed with tumeric powders), and CDPP (cow dung mixed with papaya powders) while the fourth (CDTRL) served as control (cow dung without plant powders). Thereafter, the bioreactors were monitored over 30 days for biogas yield (kg) and microbial populations (cfu/ml). As digestion ended by day 30, CDNP had the highest biogas yield (0.63 ± 0.03), followed by CDPP (0.29 ± 0.09), then CDTP (0.25 ± 0.06) while CTRL had the least yield (0.17 ± 0.03) and the various yields obtained were significantly different (p<0.05) from one another. Similarly, CDNP had the highest bacteria counts (31.02 ± 0.03), followed by CDPP (26.01 ± 0.01), then CDTP (17.01 ± 0.01) and the least count was noticed in CTRL (13.01 ± 0.02). Notably, the various bacteria counts were significantly different (p< 0.05) from one another and the bacteria isolates identified included species of Bacillus, Pseudomonas, Methanobacterium, Lactobacillus and Escherichia coli.
