Within the given diploma thesis, an overview of the development of anaerobic development is made, the process of biogas production according to the stages of decomposition and the possibility of It˙s use is explained, the parts of the biogas plant and the processes that take place in them are listed and described. This paper discusses in more detail about the cleaning and raising the quality of biogas, with an emphasis on cleaning from the hydrogen sulfide. The purpose of this thesis is to investigate the differences in the quality of biogas based on available data sources within the biogas plants for electricity production (Mitrovac and Popovac) from different types and quantities of substrates, and much attention is paid to the impact of biogas composition on the possible cogeneration of the biogas. Statistical analysis of data from the Mitrovac and Popovac biogas facilities revealed significant differences in the yield of biogas and methane depending on the substrates, and the growth of hydrogen sulfide, ammonia, carbon dioxide, nitrogen and oxygen was determined by adding certain raw materials. It is concluded that due to good construction solutions and preventive methods, significant unforeseen costs in cogeneration rarely occur. Biogas before entering cogeneration must be prescribed with certain purity and humidity. The biggest cost with regard to the composition of biogas in cogeneration is the purification of biogas, mostly due to hydrogen sulfide in crude biogas. Depending on the treatment system, the costs of cleaning and replacing the purifier, the cost of consumed activated carbon or, as in this case, the observation of biogas facilities cost consumptions of FeCl3 (iron (III) chloride).