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Comment by laputan_machine | Hacker News Reader

The angle about "reducing waste" seems a bit moot. Sand is plenty and coffee is organic.

> Sand is plenty […]

Specific sands are needed for specific purposes, and sometimes they can be a challenge logistically. Further, on human time scales, sand is a non-renewable resource:

* https://www.bbc.com/future/article/20191108-why-the-world-is...

* https://e360.yale.edu/features/the-hidden-environmental-toll...

* https://www.theguardian.com/cities/2017/feb/27/sand-mining-g...

* https://www.reuters.com/graphics/GLOBAL-ENVIRONMENT/SAND/ygd...

* https://www.goodreads.com/en/book/show/36950075

Sand for concrete is increasingly being manufactured by crushing of hard rocks.

> Sand is plenty...

Is that true? I was under the impression that suitable sand is a dwindling resource.

I was wondering the same thing about sand.

You're both correct. Building grade sand is scarce and its extraction is environmentally catastrophic.

Sand is cheaper per kilo than used coffee grounds.

"Building-grade sand" is sharp sand. It is the cheapest sand you can buy. Roman's built things out of their concrete which was full of random bits of rubble, and some of these structures still stand today.

Correction: they used lime mortar. Modern concrete was created about a century and a half ago. The random bits were chunks of lime which increased the building's hydraulic qualities - lime self heals, concrete doesn't

Yes, but concrete does not use this grade. It's crushed granite and limestone, i.e. the most sustainable. -- https://www.builderspace.com/types-of-sand-used-in-construct...

Isn't most of the planet covered in sand?

Wind blown sand isn't good for construction, since it's too round or the wrong size.

Is all the sand underwater "wind blown sand"?

I think there is a huge gap between lacking sand that is convenient for industry and no sand at all like is being claimed.

It depends on the sand / use-case. Sand in concrete is crushed granite/limestone.

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