Evaluation of Methane Production From Dairy Cow Manure and Vegetable Waste

Dairy cow manure has high buffering capacity hence a substrate for anaerobic digestion, however the process is not optimised in mono-digestion system due to limited substrate. The aim of the study was to assess the effect of co-digesting animal waste and vegetable waste on methane production. Two systems were applied- batch and continuous anaerobic digestion system to determine effect on methane yield. The experiments were conducted with treatments as- manure alone (M), composite of manure with cabbage (MC), manure with potatoes (MP), manure with cabbage and potatoes (MCP), faecal alone (F), faecal with cabbage (FC), faecal with potatoes (FP) and faecal with cabbage and potatoes (FCP). Rectal grab samples were collected prior to incubation and manure was collected from the pens. All treatments were in replicates. Composite of manure or faecal with cabbage and potatoes produced the highest biogas (FCP- 32.1 mL/g DM, MCP- 29.5 mL/g DM) and methane (FCP- 3.13 mL/g DM, MCP- 2.36 mL/g DM) compared to manure alone or faecal alone (F- 27.0 biogas mL/g DM, M- 26.6 biogas mL/g DM) (F- 1.36 methane mL/g DM, M- 1.18 methane mL/g DM). Co-digesting dairy excreta with cabbage as only vegetable substrate affected anaerobic digestion (FC- 24.8 mL/g DM, MC- 24.9 mL/g DM), since it was the lowest in biogas production compared to all treatments. The anaerobic digestion system had an effect in methane production since continuous anaerobic digestion system produced the highest methane compared to batch anaerobic digestion system in all treatments. The results obtained in this study suggest that composite of manure with both cabbage and potatoes results in the highest biogas and methane production.