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Comment by sandworm101 | Hacker News Reader

At what point does it become feasible to just manufacture sand? I know it is possible but how much more expensive must sand get before we just convert quartz mountains into sand? The article's quoted "50 billion metric tons" of needed sand isn't all that much when compared to the weight of actual mountains.

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Depending on the type of rocks and how fine you want to grind them, the Specific Energy used is between 10-100(kWh/t). That leads me to guess $8-$25 per ton of electricity used for grinding rocks into sand. I was unable to find good numbers for the capital cost.

At an aggregate mine located in Brazil, the total expenses are $80-$160 per ton [1].

The price of sand at home depot is 5.96 for a 50lb bag, $238 per ton. My conclusion is you could make sand by grinding but it would cost 50%-100% more vs. digging up the beach.

[1] https://www.scielo.br/j/rem/a/8MW5dFZc5Vh6qMdnTqRKbfM#

Edit: Chat GPT thinks it would cost $62.25/per ton make sand from rocks.

Land vs water/barge transport costs for bulk cargo may increase that by magnitude. Article suggest there will be 5x increase in demand and 5x increase in price at current stagnating availability. So that seems maybe doable.

I call shenanigans on the 5x price increase.

Marginal increases in commodity price can greatly increase supply as previously uneconomic deposits/production methods suddenly become very viable.

And while some processes critically depend on concrete, others will get pushed to other non-concrete methods if price goes up.

I think this might be case where cheap deposits are obviously geographically constrained. River sand near shores/blue water access for bulk transport to global markets. Once you expand to exploring/exploiting increasingly inland, the logistics of bulk cargo starts stacking up.

Sure, but when you double the acceptable transportation budget/distance, you square the coverage territory.

(Assuming an infinite number of routes and no change in cost per distance)

I think, unqualified speculation, transportation cost scales linearly because most economical exploitation past shores is along river/waterway sand, hence exploitation will be not be squared. Squaring coverage territory, as in getting sand from land introduces land shipping, which is even less efficient because cost per distance is subject to geography. Unless, engineered sand comes from coastal infra that takes regional inputs and pipes it strait onto barges, which also makes sense. But wild speculation on my part.

Somewhat related, these people are turning glass to sand from recycled bottles.

https://www.tv20detroit.com/news/national/turning-recycled-g...

I guess desert sand doesn’t work? That would seem like quite a big supply

Desert sand is too smooth and fine for most industrial applications. Most concrete, for example, uses sand and rocks from rivers.

There are many different types of sand for many different purposes. Sand for silicon is the most expensive. Sands for construction tend to be very cheap.

I don't think glass is appropriately pure for silicon - but that would probably be the only application for sand where it could possibly be economical to manufacture rather than extract and process.

Quite a bit, it's expensive to turn rocks into sand. Seems plausible that mines will start selling off their sand (after whatever they are mining is removed).

Is mine sand suitable? The sand used in cement is very specific shape and size. I think that is what makes it so difficult to produce.

It is not. We have an unlimited amount of desert sand available to us, but we need the river sand for construction. Otherwise the likes of Saudi Arabia would be exporting sand instead of importing it for their sky scrapers. The same is true for the mining sand, only a portion of it is appropriate for construction.

Actually that's a lie. Desert sand is fine for aggregate.

https://www.sciencedirect.com/science/article/abs/pii/S23527...

41.3mpa on pure desert sand is completely fine. Stronger than your houses slab your probably on now.

'Just' pressure is not the only metric; from your link:

> However, the flexural and tensile strengths tended to decrease as the amount of desert sand increased, particularly beyond a 25% replacement level.

So it is not a 1:1 replacement, and there are further considerations that need to be taken into account into how much (if any) desert sand can be put into a particular mix for a particular purpose. Another paper if you want to get into the weeds somewhat:

> In this paper, the effect of DSRR, temperature and cooling regime on the mechanical performances of concrete produced with desert sand was analyzed. To study the influence of temperature on the microstructure of concrete produced with desert sand, the microscopic experiments (XRD, SEM) were employed.

* https://ijcsm.springeropen.com/articles/10.1186/s40069-020-0...