The sewage treatment plant, as a producer of renewable energy, should make every effort to ensure that the biogas used as a fuel meets the quality requirements, including those of the manufacturers of cogeneration units. Such measures necessitate the application of a conditioning process of biogas in order to remove harmful compounds, so that its parameters ensure failure-free operation of engines. The aim of the research was to evaluate the effectiveness of biogas treatment in the A-type installation using the "wet biogas treatment" technology, and in the B-type installation, which is a comprehensive solution comprising sulfur removal as a result of a simultaneous regeneration of the bed with oxygen, removal of siloxanes on activated carbon, cooling and heating of biogas along with its filtration. The analysis of the results of biogas testing for these two installations demonstrated fundamental qualitative differences for the benefit of the installation B, in which the biogas was characterized by a much lower content, mainly of sulfur, hydrogen sulfide, siloxanes and humidity. The introduced pollution indicator of a megawatt hour produced in cogeneration one has confirmed much higher pollution load from the A-type installation. The hybrid solution applied in the work with simultaneous regeneration of the bed has confirmed the efficiency of biogas conditioning. Such a solution contributes to a safe and reliable operation of the cogeneration system for generating energy from a renewable source, which in turn contributes to the optimization of energy.