EVALUATION OF THE EFFECTS OF BIOCHAR ON THE BIOGAS YIELD OF POULTRY WASTES AND THE DIGESTATE

Abstract

The world at large is switching to cleaner, sustainable and eco-friendly ways of energy also known as renewable energy and one of the forms of renewable energy is biogas. This research investigates the effect of adding biochar, a product of pyrolysis of biomass under anaerobic conditions as an additive to the anaerobic digestion of poultry droppings from both layers and broilers. Six digesters were used in this research labelled as A, B, C, D, E and F, containing on dry weight basis: 100% layer wastes, 95% layer wastes + 5% biochar, 90% layer wastes + 10% biochar, 100% broiler wastes, 95% broiler wastes + 5% biochar and 90% broiler wastes + 10% biochar respectively. The temperature, pH, pressure and biogas yield were recorded daily for 30 days. The resulting biogas was then analysed using gas chromatography analysis for its constituents on the 10 th , 20 th and 30 th day of the retention period. The cumulative biogas yields from the digesters at the end of the retention period was 17.90, 17.72, 21.84, 22.56, 21.27 and 21.98L. For the layer wastes, we noticed that the biogas yield from digester D increased by 26 % from the control set-up A and digester F showed the highest biogas yield for the broiler wastes with a 24% increment from digester B. Gases collected from digesters C, D and F were analysed for their constituents and the methane content was found to be highest in the gas gotten from digester F (68.12%) which also had the least amount of hydrogen sulphide (0.84%). We found the optimum waste for biogas content due to its methane content to be broiler wastes, the optimum addition of biochar to be 10% and the resulting slurry to be odour-free due to the reduction in hydrogen sulphide and nitrogen gas as the retention time increased which is good for the environment.