Just out of curiosity is it possible to print with HDPE?
Would it be easy or hard?
I know they don't make HDPE filament* but I know people with a filament extruder could make some HDPE because it is a common plastic, which means it can be given a second use or something.
*To my knowledge
It can be done, although PE is not the best material to 3D print, as it has very low melting point (HDPE is just over 100°C), it is unpleasantly waxy to the touch and needs specialised paints and glues.
I never tried myself, but I know the RecycleBot is supposed to be able to use PE waste to produce a filament.