Utilization of Co-digestion of Local Brewery Wastes and Cattle Dung as a Potential Source of Biogas and Organic Fertilizer

Abstract

Biogas production from co-digestion of local brewery waste (BW) and cow dung (CD) was study for value added to this solid waste. The objective of this research was to fine the optimum condition for maximum biogas production and also examined the effectiveness of the biogas residue (liquor from anaerobic digestion process) as a nitrogen source for the production of okro. The experiments were performed in a laboratory scale of 1.5 liters plastic bottles were used as digesters operated in batch mode and mesophilic conditions [35°C±0.5]. The feedstock were test in the following ratios CD:BW, 90:10, 80:20. 70:30, 60:40, 50:50, 40:60, 30:70. 20:80 and 10:90. The maximum biogas yield was attained with mixtures in the proportions of 70:30 CD:BW. At these proportions, there was a biogas yield increase as compared to other ratios. The addition of BW increased the biogas yield from 0.40t/lt.day to 0.92lt/lt.day. It was found that CD: BW of 70:30 is the optimum ratio from batch process. The gradual reduction of the VFA concentration clearly indicated the stability of the process. A micro (pot) experiment was conducted to study the comparative effects of biogas residues, and NPK fertilizers on growth and yield using okro as the test crop. Twelve experimental soil filled pot in a complete randomized block design was used comprising of three each for Control T1 (no NPK and no BR), T2 100% NPK fertilizer, T3 50% BR plus 50% NPK fertilizers and T4 biogas residues (BR 100). The parameters studied showed that plant height, root length, number of fruits per plant and fruit weight was affected by the addition of biogas residue. A maximum 20.2% plant height increase over control T1 was observed in T3, 100% NPK has 10% while T4 has 8%. A maximum increase of 28.57% number of fruits was recorded in treatment T2 and T3, while 14.29% increased was recorded in T4 compared with control. The 50% BR applied in combination with 50% NPK (T3) resulted in 25.42% increase in fruit weight over control, T4 has 20.34% and 16.95% was observed in T2. Based on these results, it may be concluded that the application of approximately 50% of biogas residue and 50% inorganic fertilizer improves the production of okro.