Raw biogas is produced via anaerobic digestion, a process in which organic matter such as animal or food waste is broken down to produce biogas and biofertilizer. This happens in the absence of oxygen, in an anaerobic digester. Raw biogas from animal waste contains around 55% methane, 35% CO2 and traces of other gases such as H2S and other VOCs. In the final stages of production (upgrading), CO2 is removed from the raw biogas and compressed.
Capturing and compressing this CO2 is an essential part of the journey. Rather than being released into the atmosphere and triggering unwanted climate effects, it can be reused, injected into a CO2 pipeline, or stored underground.