In a cryogenic method, crude biogas is compressed to approximately 80 bar. The
compression is made in multiple stages with inter-cooling. The compressed gas is dried to
avoid freezing during cooling process. The biogas is cooled with chillers and heat
exchangers top K45 8C, condensed CO2 is removed in a separator. The CO2 is processed
further to recover dissolved methane, which is recycled to the gas inlet. By this process
more than 97% pure methane is obtained. No data is available on investment and
operational cost [15].