Biogas yield from carbonated soft drink sludge with some organic wastes.

An investigation was carried out on the production of biogas from carbonated soft drink sludge with some organic wastes such as palm oil sludge (POS), soybean cake waste (SW), powdered rice husk (RH) and pig dung (PD). The wastes were combined in the ratios of CS:POS (1.2:1), CS:SW (2.4:1), CS:RH (1.2:3) and CS:PD (1: 2). They were subjected to anaerobic digestion for 25 days. The mean biogas yield of CS alone was 3.46 L/total mass of slurry input. While those of CS:SW, CS:PD, CS:RH and CS:POS were 6.87, 4.86, 4.00,and 1.74 L/total mass of slurry input respectively. Results of the investigation indicated that there was increased biogas production from the combinations of CS:SW, CS:PD and CS:RH though the increase in yield of the CS:RH was not significant (p _ 0.05). The biogas yield from CS:POS was very low. Quantitative analysis of the flammable biogas from some of the blends indicated high methane contents. The CS:POS had methane (75.5%), CO2 (21.0%), CO (2.3%), H2S (1.2%), CS:SW had methane (70.8%), CO2 (21.7%), CO (7.2%) and H2S (0.3%) and CS:RH had methane (71.5%), CO2 (19.8%), CO (8.0%) and H2S (0.7%). The overall results indicate that the low yield of flammable biogas from carbonated soft drink sludge could be enhanced significantly when blended with either soybean cake waste or pig dung.