[aaron695]

Energy and water?

We are fully capable right now to recycle all our water, both in the home and on farms, it just cost a lot in materials and energy.

I don't see why energy will be scarce when we could cover the worlds oceans in solar panels (if we really had to)

Cheap labor will do amazing things, it's exponential.

Robots are cheap, solar panel installation is cheap, energy is cheaper, robots are cheaper, mining/materials is cheaper.....

[Nevermark]

Anything limited will be scarce since life and technology optimize the use of all resources.

At some point, water needs to be used for one thing, and not another. That necessary choice is what is meant by scarcity. Choices must be made, recycling water won't avoid the need to choose what to do with the water.