The paper presents the numerical simulation on combustion of Methane and biogas mixtures in the swirl burner can-Type of gas turbine combustion chamber. The study deals with the impact of mass fraction of carbon dioxide for biogas on emissions of noxious compounds during combustion. The investigations were done for four different fuels: pure Methane (100% CH4), three biogases (90%CH4+10%CO2, 75%CH4+25%CO2 and 70%CH4+30%CO2), with the constant value of equivalence ratio (f=0.95). The numerical results show that a low content of carbon dioxide in Methane-air mixture leads to a better flame stability through an increase of the volume of the recirculation zone. The numerical analysis has shown that the biogas fuel allows a reduction of about 33% on the NO emissions and about 10% on the CO emissions and carbon dioxide contained in the fuel leads to the lowering of the flame temperature, whose effect reduces NO emissions. The results of the investigation clearly demonstrate that it is possible to use such fuels in combustion systems with swirl burners.