When the biogas is used as fuel in cogeneration plants to produce electricity and heat, such admixtures as carbon dioxide, oxygen, nitrogen and small amounts of hydrogen sulphide, ammonia, etc., do not damage the plant. However, if it is desired to use the biogas as the fuel for vehicles and supply it to the natural gas network, it is excessively important to minimize the amount of these admixtures, maintaining the biomethane as pure as possible with the maximum possible concentration of methane. Several biogas purification technologies are employed globally and almost all of them contain the
primary purification stage when the harmful pollutants are removed from the raw biogas: moisture, hydrogen sulfide, ammonia, siloxanes, etc. The moisture is removed by cooling the gas to the dew point, and hydrogen sulfide, siloxanes and other pollutants are removed by filtering the biogas through carbon filters, and ammonia is removed by flushing out. The pure methane and carbon dioxide mixture is obtained after the primary purification, and it is routed to the secondary purification equipment.