Effect of Temperature and pH on the Utilization of Agro Wastes for Biogas Production

Biomass and wastes are increasingly being utilized as major energy sources not only in Nigeria, but globally. Different wastes/biomass to energy technologies have been used in the past by several researchers but anaerobic digestion seems to be the best option owing to its eco-friendliness, low cost and simplicity of its design. The work evaluated the effect of temperature and pH on the utilization of agro wastes (pig dung, goat dung, cassava peels and vegetable wastes) for biogas production using anaerobic digestion. The slurry was created in a digester by combining wastes and water in a 2:1 ratio. Under regulated environmental conditions, the anaerobic process was batched with a retention time of 21 days. On a weekly basis for three weeks, the total viable counts obtained were 8.7 × 107 CFU/mL, 2.64 × 107 CFU/mL, and 1.34 × 107 CFU/mL. As acid was created by the bacteria in the digester, the pH dropped from 7.84 to 5.53 was observed. Result showed temperature at 15 oC and 24.5 oC on day 0 and day 2 respectively, with a gradual increase recorded on day 4 until stability as the experiment progressed with an observable increase in the volume of biogas produced. The average amount of gas observed from the setup ranged from 1.7 cm3 to 23.3 cm3. Result showed no biogas production on days 0, 1, and 2, with the lowest gas production on day 4 and the highest increased volume of production (23.3 cm3) was observed on day 21. Statistical analysis utilizing one-way ANOVA revealed a significant difference of p < 0.05 between the biogas produced and experiment duration. The study demonstrates that agricultural wastes have great promise for the cost-effective production of biogas, emphasizing the importance of utilizing this medium to improve energy output.