 Corresponding author: Osuji malachy ikeokwu Copyright © 2022 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0. Comparative study of biogas formation using different locally sourced substrate Osuji malachy ikeokwu * , Chilakah godspower chukwuebuka, Anyanwu chukwubuikem Isaiah and Ndiukwu Precious Chinonso Legacy University Okija Anambra state Nigeria. Global Journal of Research in Life Sciences, 2022, 01(01), 037–043 Publication history: Received on 29 August 2022; revised on 06 October 2022; accepted on 09 October 2022 Article DOI: https://doi.org/10.58175/gjrls.2022.1.1.0026 Abstract Co-digestion method of biogas production has proved to enhance the quantity of biogas produced. Co-digestion simply means the combination of two or more substrates together in anaerobic fermentation. For containers 1, 2, 3 and 4; there is a reasonable amount of gas production for container 4 which is for co-digested substrates. The ratio of the 4 containers at day 15 shows 0.10: 0.11: 0.12: 0.16: and 0.20. This shows that containers which represent cow dungs, poultry dungs and sewage for day 3, 6, 9, 12 and 15 are in the percentage of 14.49%, 15.94%, 17.39%, 23.19% and 28.99%. The 28.99% explains why co-digestion produces more biogas. Keywords: Substrate; Co-Digestion; Anaerobic; Biogas; Methanogen; Fermentation 1. Introduction Biogas is a term used to describe a mixture of gases produced during the anaerobic digestion of biological or organic materials or waste (Choong et al 2016). By anaerobic it means oxygen is not needed for the reaction to take place. In a small scale farm, biogas can be made from the anaerobic decomposition of organic material such as livestock waste (urine, dung) and waste feeds. Biogas is produced when bacteria known as methanogen bacteria ferment or breakdown the organic material in the absence of oxygen (Jan & Felix .; 2011). Methanogen bacteria prefer certain conditions and are sensitive to the microclimate within the digester. Methanogen bacteria develop slowly and are sensitive to sudden changes in temperature (Dhaked et al 2010). For example, a sudden fall in the slurry temperature by even 2 o C may significantly affect their growth and gas production rate. Biogas consists of methane (40-70%), also known as marsh gas or natural gas (CH4), 30 to 40% carbon dioxide (CO2), and low amounts of other gases such as hydrogen, nitrogen and hydrogen sulphide. Biogas is about 20% lighter than air and has an ignition temperature in the range of 650° to 750° C. It is odourless (after burning) and colourless and it burns with a clear blue flame similar to that of Liquid Petroleum Gas (LPG) gas (Kahn et al 2016). Biogas is a renewable fuel because it is produced from waste treatment. Biogas is produced inside a plant known as a bio digester (Karanja, and Kiruiro,. 2003). Biogas production and technology has been around for a long timed and its use has been implemented all over the world. According to Harris (2015), anecdotal evidence indicates that biogas was used for heating bath water in Assyria during the 10th century BC and in Persia during the 16th century AD. In the 12th Century, Marco Polo, the famous merchant from Venice reported the use of covered sewage tanks. In the 18th century, it was determined that flammable gases could evolve from decaying organic matter, and that there was a direct correlation between the amount of decaying organic matter and the amount of flammable gas produced. In Europe in 1808, Sir Humphrey Davy determined that methane was present in the gases produced during the anaerobic digestion of cattle manure. In 1884, Pasteur researched on biogas from animal residues and proposed the utilization of horse litter to produce biogas for street lighting (Moestedt et al 2016).