NOVELTY - A process (M1) for increasing the concentration of methane gas (CH4) in a biogas stream involves: wet scrubbing the biogas stream; drying the biogas stream (upgraded biogas street); and removing hydrogen sulphide (H2S), or at least some of the H2S, from the biogas stream. The step of removing the H2S is subsequent to the drying step.    USE - For increasing the concentration of methane gas (CH4) in a biogas stream; for treating biogas stream both to increase methane content and reduce H2S content (all claimed).    ADVANTAGE - The process (M) increases the concentration of methane gas in a biogas stream; treats biogas stream both to increase methane content and reduce H2S content; reduces the levels of the impurities of a biogas feed; is a hybrid process of water scrubbing and PSA albeit in a non-obvious fashion, incorporating further steps; the second and third processes are, unusually, carried out in a single column or location; provides high performance in that levels of impurities (particularly H2S) are significantly lower that the prior art; provides gas entering the dehydration process has been cooled by-passing through the preceding wet scrubbing step. In this case the temperature of the incoming gas is approximately at the same temperature as the water scrubber operating temperature. This is cooler than the gases purified by PSA processes in the prior art. The gas temperature upon entry to a PSA column is generally around 30 degrees C. One significant advantage of our operating lower temperature is that the water content of the incoming biogas is lower than that of gas at ambient temperature. This is an advantage for our method as the column can be on line for a longer period before needing regeneration.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) treatment (M2) of a biogas stream both to increase methane content and reduce H2S content involves: at least, ia) taking a biogas stream having both a methane and carbon dioxide content and including an H2S content; iia) scrubbing the stream (optional prior modification, e.g. any at least one of compression, partition, stripping, flashing, recycle in part, etc.); iiia) drying the wet stream from step iia) stream, and iva) removing H2S from step iiia) stream to a level below 0.005%;    (2) apparatus for increasing the CH4 content of a stream of biogas comprising a wet scrubber (5), and a column. The column contains, in order of passage of the stream through it, a quantity of porous material capable of removing water from the stream, followed by a quantity of activated carbon;    (3) biogas enriched in methane and/or reduced in H2S prepared from the method (M1) or (M2); and    (4) a column for increasing the CH4 content and/or reducing the H2S of a wet stream of biogas comprising a column packed sequentially with a gas dehydrating porous material followed by activated carbon.    DESCRIPTION OF DRAWING(S) - The figure shows a process flow diagram of gas compression system.    Compressor system (1,2)    Water scrubbing system (5)    Gas recovery (6)    Process water (7)    Gas drying/purification system (8)    Condensate collector (11)    upgraded biogas (30)    Distal end. (37)