NOVELTY - A polymeric membrane comprises co-continuous, three-dimensional network of essentially two immiscible polymers and a compatibilizer (0 - 0.2 wt.%).    USE - For enriching the concentration of a gas from a gas mixture e.g. mixture of methane and carbon dioxide by using a diffusion cell (claimed).    ADVANTAGE - The membrane has high gas permeation, wide applicability, operates at ambient temperature and at low cost.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for    (1) preparing immiscible polymeric blend membranes involving:    (x) mixing two essentially immiscible polymers and the compatibilizer to create a polymer blend;    (y) extruding the polymer blend with an extruder to form an extruded sheet;    (z) either inline stretching the extruded sheet to obtain an immiscible polymeric blend membrane containing continuous interdomain spacing of less than 400 nm, or cutting the extruder sheet to create a cut extruded sheet, and offline stretching the cut extruded sheet to obtain an immiscible polymeric blend membrane containing continuous interdomain spacing less than 400 nm;    (2) treatment of organic waste material feedstock involving either:    (a) subjecting the feedstock to anaerobic digestion in a biogas reactor to create a digested product;    (b) removing biogas and ammonia from the digested product to create an aqueous/solid digested product, ammonia and biogas;    (c) separating the digested product into an aqueous fraction and a digested solids fraction; and    (d) subjecting the digested solids fraction to gasification in a gasifier operating at 700 - 1200degreesC to produce ash and producer gases, or    (3) treatment of organic waste material feedstock involving:    (a)combining the organic waste material with at least one extrinsic component to obtain a feedstock having a moisture content and a chemical content to undertake the production of a biogas during subsequent digestion;    (b)reducing the particle size of the feedstock to create a reduced particle size feedstock;    subjecting the reduced particle size feedstock to anaerobic digestion in a biogas reactor to create a digested product;    (c)removing biogas and the ammonia from the digested product to create an aqueous/solid digested product, ammonia, and biogas;    (d)separating the digested product into an aqueous fraction and a digested solids fraction;    (e)drying the digested fraction in a moisture separator to generate dried digested solids fraction;    (f)subjecting the dried digested solids fraction to gasification in a gasifier operating at 700 - 1200degreesC to produce ash and producer gases; and    (3) enriching concentration of a gas mixture.