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Biogas is a clean environment friendly fuel that is produced by bacterial conversion of organic matter under anaerobic (oxygen-free) conditions. Raw biogas contains about 55–65% methane (CH₄), 30–45% carbon dioxide (CO₂), traces of hydrogen sulphide (H₂S) and fractions of water vapour. Pure methane has a calorific value of 9100kcal/m³ at 15.5°C and 1atm; the calorific value of biogas varies from 4800 to 6900kcal/m³. To achieve the standard composition of the biogas and calorific value of 5500kcal/m³ the treatment techniques like absorption or membrane separation should be applied. In the paper the results of the tests of the CH₄ enrichment in simulated biogas mixture consisted of methane, carbon dioxide and hydrogen sulphide were presented. It was showed that using the capillary module with polyimide membranes it was possible to achieve the enrichment of CH₄ from the concentrations of 55–85 …