A methane content of over 90% must be achieved to turn biogas into biomethane. Biogas undergoes an “upgrading” or “cleaning” process to reduce its CO2 content and increase the methane (CH4) concentration from 54% to 90%.
There are various technologies capable of treating biogas to obtain biomethane, each of which can adapt to different flow rates or project requirements.
You can find further information on upgrading technology in the following content. Contact our team if you require more customised information and explore the best upgrading technology option for your project.
Chemical absorption upgrading technology
PSA upgrading technology
Certain materials, such as activated carbon or zeolites, are capable of adsorbing and desorbing CO2 and PSA systems use this property to treat biogas. The system consumes electrical energy to achieve the pressure changes required by the process. This technology enables separation of almost all O2 and N2 from methane.
PSW Upgrading methods
Paraffin/surfactant/water emulsion (PSW) harnesses the difference in solubility in water between methane and CO2 to separate them. The biogas is conducted through a pressurised water system that dissolves the carbon dioxide, enabling an output with a very high methane content.
This technology is based on chemical absorption of CO2, H2S and volatile organic compounds (VOCs) by chemical compounds such as amines or aqueous solutions of alkaline salts. It is an extremely efficient separation process, achieving a high percentage of methane with low presence of hydrogen sulphide in the renewable natural gas stream and consequently reduced methane losses in the off-gas.
Cryogenic upgrading technology
The different boiling points of methane (-160 °C) and carbon dioxide (-78 °C) enable cryogenic separation with CO2 recovery in liquid state. This system is of particular interest for production of bio-LNG due to the of biogas output conditions.
Membrane upgrading technology
Biomethane with a high degree of purity can be obtained by pressurising biogas and forcing it through selective membranes. The process can be optimised by enabling numerous stages to progressively upgrade the source gas. It is a robust technology in spite of the fact that it responds poorly to flow-rate variations.