NOVELTY - Anaerobic process comprises adjusting concentrated carbon dioxide flow, preparing of nutritional substrates containing monomeric and/or oligomeric organic substances and high alcohol content substrates for selected mixed bacterial populations, feeding the selected mixed bacterial populations with substrates, and supplying the carbon dioxide of the flow to the selected mixed bacterial populations.    USE - An anaerobic process for converting carbon dioxide into methane (claimed) used for industries emitting greenhouses gases as well as for any plants involved in the production of energy from biomass or in the disposal of organic waste, such as production of energy from renewable sources, waste disposal industry, and agricultural production.    ADVANTAGE - The method reduces the emission of greenhouse gases into the atmosphere, produces biogas/energy from carbon dioxide and biomasses, allows recycling organic waste as opposed to landfill disposal, and uses agro-energetic cultures and agricultural residues. The method is very fast and compact because it incorporates advanced biotechnological innovations. The method can economically recycle it into a valuable energetic product with large market while at the same time having favorable consequences on the environment.    DETAILED DESCRIPTION - Anaerobic process comprises adjusting concentrated carbon dioxide flow (phase A), preparing of nutritional substrates containing monomeric and/or oligomeric organic substances for selected mixed bacterial populations by starting from a first portion of the biomasses (phase B), preparing high alcohol content substrates for selected mixed bacterial populations by starting from second portion of the biomasses (phase C), feeding the selected mixed bacterial populations with substrates and supplying the carbon dioxide of the flow to the selected mixed bacterial populations so that it is converted into methane during multi-stage anaerobic process (phase D). The carbon dioxide is captured from combustion system or another industrial process. The anaerobic process uses formulated and pretreated biomasses and is based on selected mixed bacterial populations INDEPENDENT CLAIMS are included for:    (1) methane producing plant comprising second module, third module, and fourth multi-stage module; and    (2) energy producing plant from biomasses and carbon dioxide comprising methane producing plant, and combustion plant.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the basic configuration of integrated process.