Evaluation of biogas production and bacterial load from co-digestion of chicken manure with different types of household waste

Background: The aim of this study was to evaluate the biogas production of chicken manure (CM) co-digestion with different types of household waste (soft organic [SO] and food waste [FW]), as well as to evaluate the bacterial load of feeding stock and digested slurry samples before and after anaerobic digestion (AD). The experiment was carried out using lab-based prototype digesters for co-digestion of CM with different household wastes (5%). Three experimental groups (T1, T2, and T3) were designed using mixing ratios of SO:CM:H2O:inoculum (5:22.5:22.5:50), FW:CM:H2O:inoculum (5:22.5:22.5:50), and (SO + FW):CM:H2O:inoculum (2.5 + 2.5:22.5:22.5:50). The digesters were set at 28-34 degrees C for 30 days for hydraulic retention time (HRT). Total viable count (TVC), Escherichia coli, and Salmonella spp. counts were determined using the spread plate technique. Results: The study revealed that the highest average cumulative biogas yield was achieved from T1 > T3 > T2, but the concentration of CH4 was found in T3 > T2 > T1. The biogas production between the three groups was statistically nonsignificant (p > 0.05) but the daily concentration of CH4 was found statistically significant (p < 0.05). The average concentration of CH4 and CO2 in biogas was found to be 30% and 68% for T1, 60% and 37% for T2, and 69% and 27% for T3. However, the H2S content was within the acceptable range. The bacterial load was decreased by 2-3 logs before and after AD, and this reduction was statistically significant (p < 0.05). Conclusion: The research found that the co-digestion of CM with combined household wastes increased the methane concentration in biogas.