The biogas from anaerobic digestion generally contains high percentage of methane, variable percentages of carbon dioxide (CO2), water vapor, sulfur compounds, nitrogen, oxygen and siloxanes.

The upgrading removes unwanted components and any other impurities from the biogas to obtain a relative profit in methane (≥ 95%) and make the biomethane completely similar to natural gas.

Upgrading system can remove carbon dioxide (CO2), water vapor and other substances but it also compresses the methane to use it in the gas network.

The technologies available for Upgrading are based on various chemical-physical principles related to the separation of gases (adsorption, absorption, permeation and cryogenesis). The decision which technologies to be used, is based on the compositional characteristics and on the volumes of the biogas to be treated. Depending on these variables, some technologies are more convenient than others.