Since I was a child, something that would occasionally worry me is the future metal crisis, and the concrete crisis.

Metal is nonrenewable resource, and while it can be recycled once something is an alloy, can we melt it back into its pure forms?

Some can be, but from what I understand not all of them can. And even for what can, it is such a difficult process I feel so hypocritical to use metal items when another material would do just fine.

And as for concrete: what do we do with it when it's garbage? Can we recycle it? (edit: yes we can)

I hope the new world comes before these things.