NOVELTY - The bioreactor for the production of biogas, comprises a liquid phase bioreactor medium activated by biological degradation of organic substances in anaerobic conditions for producing fuel gas and carbon dioxide, a gas phase containing a biogas product in exchange with the liquid phase through liquid-gas, a control unit for regulating the production of biogas with the introduction of the chemical substance in liquid phase, and a movable injector. The control unit is equipped with a unit comprising a predetermined function that calculates a resulting value.    USE - The bioreactor is useful for the production of biogas including methane and carbon dioxide.    ADVANTAGE - The bioreactor ensures easy and economical production of biogas with high yield, disrupts the growth of microorganisms during the production of biogas, and minimizes the effect of organic overloading.    DETAILED DESCRIPTION - The bioreactor for the production of biogas, comprises a liquid phase bioreactor medium activated by biological degradation of organic substances in anaerobic conditions for producing fuel gas and carbon dioxide, a gas phase containing a biogas product in exchange with the liquid phase through liquid-gas, a control unit for regulating the production of biogas with the introduction of the chemical substance in liquid phase, and a movable injector. The control unit is equipped with a unit comprising a predetermined function that calculates a resulting value with respect to the carbon dioxide content present in the biogas. The resulting value represents a desired content of carbon dioxide dissolved in the liquid medium. The control unit is arranged for controlling a parameter such as flow of chemical substance in a direction to reduce the content of carbon dioxide. The flow is controlled in an integral proportional mode based on a difference between the content of carbon dioxide measured in the biogas and a determined value, and in a static manner based on the alkalinity in liquid phase, a content of carbon dioxide dissolved in liquid phase and the content of carbon dioxide measured in the biogas. The movable injector is placed at a level of a recirculation loop. The chemical substance is an alkaline agent, and an acid agent. The bioreactor medium comprises microorganisms capable of synthesizing methane. An INDEPENDENT CLAIM is included for a process for producing biogas in a bioreactor.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a bioreactor for the production of biogas.    Fermenter (100)    Interface (102)    Carbon dioxide sensor (106)    Alkaline container (110)    Acid container. (112)