The present disclosure refers to a plant (1) for production of biogas (18). The plant (1) comprises a digester (4) including a bag like casing (5) of flexible material and fluid tight wherein the bag like casing (5) is adapted for the containing a sewage (14). The casing (5) defines in an internal zone a digestion chamber (40) adapted for a digestion of the sewage (14). The plant (1) further comprises a heater (45 68) for heating the sewage (14). The disclosure further refers to a co generation installation (100) comprising a plant (1) for the production of biogas (18) a co generator (8) and fuelling means (71 72) for fuelling the co generator (8) with biogas (18) said fuelling means comprising a biogas line (71 72) between the plant (1) and the co generator (8).
