Production and Characterization of Biogas from Cow Dung, Poultry Manure and Their Co-digestion

Abstract

The global demand for energy grows rapidly, and therefore, it is a time to look alternative and renewable resources of energy to replace fossil fuels that harm the environment. On other hand, improper waste management creates environmental pollution and makes it unpleasant and unattractive for residences. Cow dung and poultry manures are the wastes produced from livestock and chicken, and they are important feedstock for biogas production. The main objectives of the present study was therefore, production of biogas from cow dung, poultry manure and their co-digestion, and evaluate the effect of biogas production parameter on the performance of anaerobic digestion process. In this study, batch mode of experimental digesters operated for 60 days at 37±0.5°C using five different ratios of cow dung to poultry manure mixtures as a feedstock. The feedstock were 100% of cow dung (T 1), 100% of poultry manure (T 2), 50% cow dung and 50% poultry manure mixture (T 3), 75% poultry manure and 25% cow dung mixture (T 4) and 75% cow dung and 25% poultry manure mixture (T 5). The feedstock was characterized in terms of moisture contents (MC), total solids (TS), volatile solids (VS), pH, organic carbon (OC), total Kjeldahl nitrogen (TKN), carbon to nitrogen ratio (C: N) and ash contents (AC). Each digester was operated in triplicate and one way ANOVA was used to compare the characteristics of feedstock, amount and chemical composition of biogas produced from the different mixtures of feedstock. The volatile solid (VS) content was more than 58% in all feedstock and, which indicates that, the feed-stocks were biodegradable and suitable for biogas production. The Carbon to Nitrogen (C: N) ratio was in the range of 6.26±0.25 to 28.75±1.23. Lower C: N ratio (T 2) indicates the biogas produced from this feedstock will be low and hence T 2 is less preferred for biogas production. The pH value of all the feedstock were feasible for biogas production, except T 1 (6.3), and significant difference was observed in all parameters among the feedstock. The total amount of biogas produced from T 1, T 2, T 3, T 4 and T 5 was 2820ml, 1509ml, 3994ml, 15796ml and 6709ml, respectively. The highest biogas yield was recorded in T4. The quality of biogas in term of methane content was 56.3±0.91, 56.9±10, 57.8±0.95, 60.7±0.1 and 63.6±0.7 for T 1, T 2, T 3, T 4 and T 5, respectively. In general, the present investigation revealed that, co-digestion encourages the feasibility of biogas from these feedstock. Even though, the methane concentration is higher in T 5, T 4 (75% poultry manure and 25% cow dung mixture) can be considered as the best feedstock for biogas production as it gives significantly high biogas yield as compared to the others. However, optimization of production parameters and analyzing other production factors need to be investigated in the future.