The methane-rich product gas can be used for different purposes. One of the options is to inject the obtained gas into the natural gas grid. Another option is to use the gas as transport fuel (CNG) for cars. Biomethane is a CO2 neutral, clean fuel without particles, that provides a good alternative to fossil fuel. The CO2 that is removed from the biogas can be recovered and liquefied to create an extra source of revenue for the plant owner.