Abstract: The invention concerns a district energy system comprising: —at least one cogeneration or heat pump unit —a first pipe system for district heating and/or cooling consisting of at least one liquid or vapor CO2 pipe; characterized by the fact that is also comprises a second pipe system consisting of at least one fluid line for the transport of CO2 or O2. The invention also relates to the use of a district energy system comprising: —at least one cogeneration or heat pump unit, —a first pipe system, —a second pipe system; characterized by the fact that that liquid or vapor CO2 is used in the first pipe system for district heating and/or cooling and that a fluid of CO2 or O2 is used in the second pipe system.