an expandable media filter structure is composed largely of biodegradable materials and is environmentally disposable . a plurality of pleated panels are interconnected at their edges so as to be collapsible for storage and shipping purposes but expandable for installation and use . a plurality of ribbons are ultrasonically welded to each of the panel edges , with the ribbon portions between edges being of substantially equal lengths , thereby maintaining equal spacing between the panel edges when the filter is in the expanded condition but allowing an easy collapsing of the filter for storage . forming a part of the nondisposable framework for support of the disposable filter are a pair of end plates which are c - shaped in cross section for slidably receiving an end panel of the media filter therein . the depth of the c - shaped channel is sufficient to allow a plurality of the unexpanded pleats to be stored therein so that a single sized filter may be used for various sizes of cabinet openings . the end plates include a pair of slots formed near their ends for attachment to a nondisposable support structure . the nondisposable support structure comprises a pair of molded plastic side caps that fit over the respective ends of the filter panels and the end plates . each side cap has a pair of flanges at its opposite ends which act to maintain the filter in its expanded condition when the end plates are placed in abutting position therewith . each side cap also includes a boss which fits into a respective end plate slot to hold the end plates in their installed positions within the side caps .