Investigation into the Use of Anaerobic Co-digestion of Cow Dung for Biogas Production

Abstract

The research is targeted on investigating the use anaerobic co-digestion of cow dung for biogas production, and to influence a decrease in the concentration of sulphide using direct inclusion of facultative lagoon sediment with sodium and calcium alginate. It was noted that 1 minute concentration of calcium alginate and sodium was introduced right from the beginning of the anaerobic digestion cycle shows the tendency to increase methane concentration and reduce the hydrogen sulphide concentration of the system. The alginates represented chelating ligands and brought about the improvement in the production of methane and decrease in sulphide concentration. This research recommends the soaking liquor exploiting cow dung (fleshing) in the ratio of 2:1 for anaerobic co-digestion. Results shows hydrogen sulphide (H₂S) concentration of fleshing to cow dung ratio without sodium alginate for 1:0.5 H₂S concentration (ppm), 1:2 H₂S concentration (ppm), 1:0 H₂S concentration (ppm) and 1:1 H₂S concentration (ppm) against time (days) and digestion flow from combined liquor and demonstrates inconsistency in movement of H₂S concentration in the beginning and maintained a rise and fall continually. It was discovered that the ratio 1:2 of fleshing to cow dung can be used to produce biogas of 45.5% v/v methane concentration. Addition of sodium alginate can give highest methane concentrations in shorter retention time and higher biogas volume than addition of calcium alginate beads. The calcium alginate beads were generally limited due to mass transfer phenomenon. The research also shows that methane concentration obtained was 57.1% v/v < 60%v/v in the application of sodium alginate. This was caused by mass transfer limitation as calcium alginate beads will have less surface area if any reaction must occur. However, it was still higher in methane concentration than digesting the substrates without alginates