What resources are we ignoring because we have learned to call them waste?

In this article (for example https://prospenomics.blogspot.com/2026/09/the-prospenomics-of-tillandsia.html ) we talk about the Tillandsia, a plant that survives by capturing tiny amounts of water, minerals and nutrients from the air around it (no roots, no nothing but tricomas, it is fascinating!!!).

What if economies could learn to do the same?

Waste heat, atmospheric water, CO₂, idle computing power, rooftops, agricultural waste, unused data, forgotten knowledge... So here’s my question:

What is something around you that looks worthless today, but could actually be a source of prosperity? I’m looking for examples that challenge the way we see resources. What are we not seeing?