Process for injecting biomethane into a natural gas network

A process for injecting biomethane into a network which has a gross calorific value of value X between XI and X2, comprising the injection of nitrogen into the biomethane network before the injection of the biomethane into the network which has a gross calorific value of value X so as to reduce the calorific value of the biomethane network to a value between XI and X2, with the nitrogen derived from the retentate of at least one membrane stage. 种用于将生物甲烷注入到具有在X1与X2之间的值X的总热值的网络中的方法，该方法包括在将该生物甲烷注入到该具有值X的总热值的网络中之前将氮气注入到该生物甲烷网络中以便将该生物甲烷网络的该热值降低至在X1与X2之间的值，其中该氮气衍生自至少个膜阶段的渗余物。