A biogas upgrader is a facility that is used to concentrate the methane in biogas to natural gas standards. The system removes carbon dioxide, hydrogen sulfide, water and contaminants from the biogas. The solution is the use of biogas upgrading or purification processes whereby contaminants in the raw biogas stream are absorbed or scrubbed, leaving more methane per unit volume of gas.
There are four main methods of upgrading: water washing, pressure swing adsorption, selexol adsorption, and amine gas treating. This purified biogas is also called biomethane.