A lightweight, non water retaining, biodegradable soil replacement material which may be charged into a flexible non biodegradable synthetic bag. The fill material may be expanded polymeric materials to afford lightweight, insulation and adequate drainage which may be charged into a flexible bag having a mesh composition. The product may be used against foundations, walls, retaining walls, piers, columns, weeping tiles or any other structure where backfill is required. The product may have other applications due to its insulating ability which do not include soil replacement but may simply be to fill a space or opening.