Experimental Characterization of Influential Parameters of Cow Dung Substrates in Biogas Production

The present work on the production of biogas from cow dung substrates was carried out at the Laboratory of Renewable Thermal Energy (L.E.T.RE) of the Joseph KI-ZERBO University in collaboration with the National Program of Biodigester of Burkina Faso (PNB-BF). We focus in this work on the determination of the physicochemical characteristics of the substrates allowing the follow-up of the biogas production. We experimented with anaerobic digestion for 100 days each at mesophilic temperature, i.e. a hermetic enclosure included between 27 and 38∘C. The average flow of biogas is Q = 2.5 m3 d -1, and that of methane is 1.9 m3 d -1. This methane-rich gas CH4 with a flow rate of 1.9 m3 d -1, i.e. a rate of 60% in the biogas, has a high energy capacity of 23kJm-3 and can be used for cooking and lighting especially in rural areas. The following physicochemical characteristics were observed for cow dung: dry matter 11.85%, volatile matter 58.83%, hydrogen potential 7.01, density 731 kg.m-3, carbon content 33.32%, nitrogen content 1.46%, nitrogen-carbon ratio 24.70, acids are around 0.18 kgCODm-3, and the average chemical oxygen demand 30 kgCODm-3. This characterization was performed on a 4m3 pilot bioreactor with daily substrates loading ranging from 20 to 30 kg. The temperature of the reaction medium remained around 35∘C, optimal for the mesophilic operation of the bioreactor. The results obtained making it possible to demonstrate the possibility of producing a large quantity of flammable biogas in a continuous manner are in agreement with the literature on methanization.