NOVELTY - The device (3) comprises a degassing tank (8), a degassing unit, and a reservoir containing a pressurized liquid. The degassing unit is configured such that it is adapted to allow an abrupt change of a pressure of the liquid under pressure at an outlet of the reservoir while providing a separation of liquid and carbon dioxide, and is formed by a conduit (9) that is connected to the reservoir at one end and opens at an opposite end into the degassing tank, a relaxation valve mounted on the conduit, and a mixer placed in the conduit.    USE - The device is useful in an installation for recovery of methane and carbon dioxide from liquid and a biogas under pressure (claimed), where the biogas is a combustible gas from the fermentation of organic waste of animal or plant in the absence of oxygen.    ADVANTAGE - The compact and stable device ensures energy-efficient recovery of methane and carbon dioxide.    DETAILED DESCRIPTION - The device (3) comprises a degassing tank (8), a degassing unit, and a reservoir containing a pressurized liquid. The degassing unit is configured such that it is adapted to allow an abrupt change of a pressure of the liquid under pressure at an outlet of the reservoir while providing a separation of liquid and carbon dioxide, and is formed by a helicoidal conduit (9) that is connected to the reservoir at one end and opens at an opposite end into the degassing tank, a relaxation valve mounted on the conduit and a mixer placed in the conduit. The free liquid of carbon dioxide and extracted carbon dioxide is discharged from the degassing tank to an outlet conduit. The conduit extends along the degassing tank such that, in the outlet conduit, the carbon dioxide escapes and the liquid contained in the reservoir flows into the degassing tank, and extends around the degassing tank from a lower part to an upper part of the degassing tank. The reservoir is placed partially in the degassing tank so that the free liquid of carbon dioxide surrounds the reservoir on a part of its height. The degassing tank is partially buried. The carbon dioxide is derived from a biogas under pressure, and is dissolved in the pressurized liquid. The free liquid of carbon dioxide contained in the degassing tank is renewed in another reservoir by a pumping unit. INDEPENDENT CLAIMS are included for:    (1) an installation to recover carbon dioxide from biogas; and    (2) a method for recovery of carbon dioxide from biogas.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of an installation including a device for recovering carbon dioxide (Drawing includes non-English language text).    Filling column (2)    Recovery device (3)    Patch area (4)    Degassing tank (8)    Conduit (9)    Evacuation opening (13)    Bottom of degassing tank. (19)