Hi Liam
Whilst waste is a broad, complex issue – the quantities of HDPE waste are not significant. If you’re looking to reuse discarded HDPE, we highly encourage this as a great “circular economy” pathway.
You could consider the design life and replacement cycle of major in-ground HDPE network infrastructure (utilities). As these are replaced, instead of transferring these back to the mainland, you could make some assumptions on application for adaptive reuse to support your design idea.
Cheers
Tom Nguyen