A Comparative Study on the augmentation of Biogas Production from Water Hyacinth and Cow dung Mixtures Using Wood Biochar and Faecal Sludge Biochar
Tumwesigye, Rodney Spencer
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The use of biomass as a renewable energy resource has become popular in recent years because of the reduction on dependence on fossil fuels and the reduction of greenhouse gas emissions to the atmosphere. Water hyacinth (WH) is popular for causing severe environmental degradation and being an economic burden to manage. However, it offers substantial prospects if exploited, especially by rural communities. Tropical climate, eutrophic conditions and the weed’s reproductive capacity promote the proliferation of the plant in regions where it has been introduced. Regarded among the world’s worst invasive weeds, WH is nearly impossible to control and eradicate without an integrated approach and community participation. Water hyacinth being a lignocellulosic biomass has great potential for biogas production. Codigestion of this weed with cow manure has been correlate process parameters and improve biogas yield however, the challenges of process instability and production of carbon dioxide have reduced efficiency of anaerobic digestion processes. Addition of biochar has been suggested to address these challenges, however little comparative work has been done on utilization of both plant-based and animal-based biochar in influencing anaerobic digestion. This study evaluated the influence of both wood biochar and faecal sludge biochar on anaerobic co-digestion of cow manure and water hyacinth mixtures under mesophilic temperatures of 37℃ for 40 days. The substrates and biochar were characterized to ascertain their physical and chemical composition relevant to anaerobic digestion. From the laboratory-controlled biodegradability test, cow manure alone had the lowest methane yield of 49.43 – 85.08 mL CH4/gVS. Addition of 2% biochar (both wood and faecal sludge) to the cow manure alone greatly increased the methane yield by 76.8% and 94% respectively while addition of 2% biochar (both wood and faecal sludge) to the 50%CD: 50% WH mixture resulted in only a 20% and 37% increase in methane yield respectively. Addition of both forms of biochar to the reactors reduced the percentages of carbon-dioxide produced from each ratio considered. Statistical analysis revealed that addition of wood biochar was not significant, while addition of faecal sludge biochar was statistically significant.