NOVELTY - Preparing a carbon dioxide and methane, comprises: reducing a partial carbon dioxide content in a treated gas mixture that is charged by a carbon dioxide binding agent in a medium of reactor vessels; and supplying a continuous feed of the treated gas mixture into a treatment plant. The first reactor vessel is in a normal operation phase, in which the gas mixture is processed by the binding agent, and a loading phase, in which the second reaction vessel is emptied and filled with carbon dioxide during the normal operation phase of the first reactor vessel.    USE - The method is useful for preparing a carbon dioxide and methane contained in a gas mixture such as landfill gas, mine gas or biogas (claimed), where the gas mixture is useful in gas-powered power plants.    ADVANTAGE - The method effectively enriches content of methane in a cost-effective manner.    DETAILED DESCRIPTION - Preparing a carbon dioxide and methane: reducing a partial carbon dioxide content in a treated gas mixture that is charged by a carbon dioxide binding agent in a medium of reactor vessels exceeding a predetermined degree of saturation of the medium bound with the carbon dioxide binding agent, after which the carbon dioxide binding agent of the reactor vessel is replaced; and supplying a continuous feed of the treated gas mixture into a treatment plant having the reactor vessels. The first reactor vessel is in a normal operation phase, in which the gas mixture is processed by the binding agent, and a new loading phase, in which the second reaction vessel is emptied and filled with carbon dioxide during the normal operation phase of the first reactor vessel. An INDEPENDENT CLAIM is included for a processing plant for continuous operation of a gas mixture containing carbon dioxide and methane, comprising: reactor vessels, through which the gas mixture is passed for partial carbon dioxide content reduction, where the reactor vessels are arranged fluidly in parallel between a supply of the gas mixture to the processing plant and a discharge of the treated gas mixture from the processing plant; and controllable valves connected with the reactor vessels.