This study investigated the effect of abattoir cow liquor waste (CLW) on biogas production of some agro-industrial wastes. The wastes; brewery spent grain (BS), cassava waste water (CW) and carbonated soft drink sludge (CS) were combined with definite proportions of cow liquor waste to produce biogas under anaerobic digestion for a 25 day retention period. The wastes were combined in the ratios: CLW:BS (1:1), CLW:CS (3:1) and CLW:CW (1:3). The results obtained indicated increased biogas production when BS and CW were inoculated with CLW, while it had a negative effect on CS. The mean biogas production of BS and CS were 7.34 and 7.1 L, respectively, while CW had no biogas production. When inoculated with CLW, the mean biogas production of BS increased to 24.53 L. CW experienced gas production with mean biogas yield of 8.23 L while the gas production of CS reduced to 2.54 L. The CLW:BS blend had the shortest time lag from gas production to onset of gas flammability of 6 days while CLW:CW and CLW:CS had time lag of 8 and 9 days respectively. The retention times for the CLW:CW and CLW:CS was 14 and 18 days, respectively. Overall results indicated that while the low biogas and/or flammable biogas production of brewery spent grain could be enhanced significantly in the presence of cow liquor waste. Cassava waste water which could not produce biogas could be made to be a cheap source of biogas by inoculating it with cow liquor waste.
Keyword: Agro-Industrial wastes, biogas production, flammable biogas production, biogas yield, waste combination.
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