To make a window envelope completely biodegradable, material which will break down in a landfill must be used for the window patch. To assist you in making a total 100% biodegradable claim, National Envelope offers patch materials made from glassine and PLA and cellulose acetate films, wood pulp products which is biodegradable.
Any window envelope made by National Envelope can be specified on a "special make" basis with a biodegradable window film. Both poly and clear window versions are available.