The chemical synthesis section is modelled in detail, to obtain a reliable dimensioning of the units. H2 is produced in an alkaline electrolyser, whose cost is 1200 €/kWel. The CO2 methanation reactor is a fixed-bed reactor dimensioned to reach grid-compliant SNG after upgrading (excess CO2 and H2 removal). For the upgrading the same membrane as for biogas upgrading is used . The grid regulations are set to a maximum of 2% H2 and 4 % CO2 .