Abstract
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.
Highlights
The Environmental consequences of animal manure disposal have motivated experts to seek for strategies which could lead to sustainable farming
3.1 Effect of Dairy Manure Co-digested with Vegetable Waste on Biogas Production
The highest biogas production was achieved from co-digestion of dairy manure, cabbage and potatoes (FP: 32.6 mL, faecal with cabbage and potatoes (FCP): 32.1 mL, manure with cabbage and potatoes (MCP): 29.5 mL)
Summary
The Environmental consequences of animal manure disposal have motivated experts to seek for strategies which could lead to sustainable farming. Manure is one of the biodegradable products and should not be disposed in landfills since it contains substantial levels of harzadous pathogens and nutrients (Neshat et al, 2017). Any mismanagement of this valuable waste may lead to contamination of water sources, soil, air pollution, and harmful microbial build-up in the environment. Anaerobic digestion is one of the best waste management practices, whereby biogas and quality fertilisers are produced. Anaerobic digestion is the process by which microbes’ breakdown organic material under oxygen free environment to produce mainly methane and carbon dioxide (Sebola, Tesfagioggis, & Muzenda, 2014)
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