NOVELTY - Preparation of a purified methane comprising gas stream (P) from a methane containing gas stream (A), comprises: pressurizing the methane containing gas stream (A) and subsequently cooling it, to give a stream comprising condensed contaminants (C) and a methane comprising stream (B); optionally feeding the methane comprising stream (B) to an adsorption and/or a catalytic conversion unit, to decrease the concentration of contaminants in stream (B); and cooling the methane comprising stream (B) to a temperature, which is sufficient to condensate carbon dioxide from the stream (B), to give (P).    USE - The process is useful to prepare the purified methane comprising gas stream (P) from the methane containing gas stream (A) (preferably a purified biogas obtained from a landfill, a digester and/or a wastewater treatment facility) (claimed). The purified methane comprising gas stream (P) is useful as an efficient energy source.    ADVANTAGE - The process provides pure methane comprising gas stream. The process is simple. The process provides a clean gas having low level of contaminants, for the problem-free application in a gas engine. The gases obtained from the purified process have the quality, which is comparable that of the natural gases. The process produces little waste.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for apparatus for producing a purified methane comprising gas stream (P) from a methane containing gas stream (A), comprising: (a) a compressor for pressurizing the methane containing gas stream (A) and a cooler located downstream the compressor; (b) optionally an adsorption unit and/or catalyst conversion unit located downstream from the compressor and the cooler; and (c) a cooler unit comprising an outlet for condensated carbon dioxide and an outlet for the purified methane comprising gas stream (P).    DESCRIPTION OF DRAWING(S) - The figure represents the schematic representation of the process of biogas:    Biogas source (A)    Purified gas (P)    Methane comprising stream (B)    Stream comprising condensed contaminants (C)    Condensed carbon dioxide (E)