Abstract

In this study, Cladodes, which is a plate like section of Opuntia ficus indica, were characterized for their physical properties, total solids (TS) and volatile solides (VS) and they were assessed in five combinations with or without cow dung for their suitability to biogas production in 2.8 L triplicate batch digesters. The highest total biogas yields were obtained from T₅ (75% Cow dung: 25% Cladodes combination) as 14.183 L followed by T₁ (cow dung alone) as 13.670 L (0 .022 m³/kg) and the lowest was from T₂ (Cladodes alone) as 6.176 L. The percentage of methane gas obtained from the experiment for treatments T₁, T₂, T₃ (50% cow dung: 50% cladodes), T4 (25% cow dung: 75% Cladodes) and T₅were 66.33, 53.16, 63.84, 52.1 and 69% respectively. Among all treatments, T₅was found to produce high methane percent of the biogas. Treatments (T₁ and T₅) that have a C:N ratio within the range of 20 to 30 were found to perform better in biogas yield and methane production than those that are not. Statistical test showed that the biogas and methane content of the gas produced by T₅vary significantly at 0.05 level except with T₁ and T₃ which means the biogas and methane content of the gas produced by T₁ and T₃ were comparable with that of T₅. The experimental findings further showed that the composition of methane for all treatments were within the range of 50 to 70%. The finding further revealed the suitability of the substrate as a supplement feedstock with the conventional cow dung for biogas production and if suitable materials for co-digestion, such as manure, are not available, Cladodes can be digested alone.

Key words: Biogas, percentage of methane, co-digestion, Cladodes, cow dung.