Biogas, with its production and energy potential, is an important renewable energy source for the developing renewable energy market. Biogas is a type of fuel that is produced from the biochemical degradation of biomass. It has a density similar to oxygen and before the biogas can be used, it is necessary to remove the contaminant gas content. Biogas is a gas obtained by degradation of biological wastes in an anaerobic environment. The contaminants in the biogas can decrease the lower heating value of the fuel and also cause corrosion and rust in the equipment and components used. Therefore, before using biogas, it is necessary to remove contaminants in it. In this study, biogas has been produced from animal waste by co-fermentation method. In order to purify the produced biogas from the pollutant gases, the effect of granular slag (an iron steel plant waste) in H2S removal from the biogas, has been investigated experimentally for different pressures. Experiment results gave an average amount of biogas production of 1.6 m(3) / day and methane (CH4) content reaching up to 71%. At the end of the process, it was determined that the 278 ppm H2S value of the biogas measured before entering the purification tower with slag material was purified with a ratio of 31% and decreased to 192 ppm without significant loss of methane.