A paperboard assembly for food box includes a piece of paperboard and a layer of cross linker is attached to at least one of inner surface and outer surface of the paperboard. At least one bio-degradable surface layer is attached to the layer of cross linker by way of heat-and-press. The At least one bio-degradable surface layer is made by way of supercritical CO.sub.2 Microcellular Foaming in Extrusion Process.