source: Arbeitsblatt DVGW G 260(A)

Gas composition (molar fraction):
methane: 96.15 %
nitrogen: 0.75 %
carbon dioxide: 2.9 %
oxygen: 0.2 %

Wobbe-Index (normal conditions) : 13.9 KWh/m³
HHV (normal conditions) : 10.6 KWh/m³