Installation for the membrane permeation treatment of a feed gas flow containing at least methane and carbon dioxide, comprising: - a compressor A for compressing the feed gas flow, - a first membrane separation unit able to receive the gas flow coming from the compressor and to supply a first permeate and a first retentate, - a second membrane separation unit able to receive the first retentate and to supply a second permeate and a second retentate, the second permeate being configured to be recycled into the feed gas flow downstream of the compressor A, - a third membrane separation unit able to receive the first permeate and to supply a third permeate and a third retentate, the third retentate being configured to be recycled to the compressor A used for compressing the feed gas flow, with each membrane separation unit comprising at least one membrane that is more permeable to carbon dioxide than to methane, - at least one measurement means for measuring the aspiration pressure of the second permeate of the second membrane unit, - at least one measurement means for measuring the methane CH4 concentration in the second retentate, - at least one compressor B for aspirating the second permeate and adjusting the pressure of the second permeate according to the aspiration pressure measured and the methane concentration measured before recycling the second permeate into the feed gas flow downstream of the compressor A, - at least one pressure adjustment means for adjusting the pressure of the feed gas flow according to the CH4 concentration measured, the pressure adjustment means for adjusting the pressure of the feed gas flow being the compressor A or a progressive shut-off and pressurization valve, and - data transmission and data processing means configured to automatically: compare the measured aspiration pressure of the second permeate and the measured methane concentration in the second retentate against setpoint values, and adjust the pressure of the second permeate and the pressure of the feed gas flow. - a compressor A for compressing the feed gas flow, - a first membrane separation unit able to receive the gas flow coming from the compressor and to supply a first permeate and a first retentate, - a second membrane separation unit able to receive the first retentate and to supply a second permeate and a second retentate, the second permeate being configured to be recycled into the feed gas flow downstream of the compressor A, - a third membrane separation unit able to receive the first permeate and to supply a third permeate and a third retentate, the third retentate being configured to be recycled to the compressor A used for compressing the feed gas flow, with each membrane separation unit comprising at least one membrane that is more permeable to carbon dioxide than to methane, - at least one measurement means for measuring the aspiration pressure of the second permeate of the second membrane unit, - at least one measurement means for measuring the methane CH4 concentration in the second retentate, - at least one compressor B for aspirating the second permeate and adjusting the pressure of the second permeate according to the aspiration pressure measured and the methane concentration measured before recycling the second permeate into the feed gas flow downstream of the compressor A, - at least one pressure adjustment means for adjusting the pressure of the feed gas flow according to the CH4 concentration measured, the pressure adjustment means for adjusting the pressure of the feed gas flow being the compressor A or a progressive shut-off and pressurization valve, and - data transmission and data processing means configured to automatically: compare the measured aspiration pressure of the second permeate and the measured methane concentration in the second retentate against setpoint values, and adjust the pressure of the second permeate and the pressure of the feed gas flow. <EOS>