The Earth's crust contains 0.1% phosphorus by mass. It’s not going to run out, at worst it’s going to cost more to extract. Granted paying more than $425/ton might have an impact on food prices, but it’s currently a very low fraction of food prices. About 20% of overall fertilizer costs.

https://en.m.wikipedia.org/wiki/Phosphorus, https://farmdocdaily.illinois.edu/2017/07/fertilizer-costs-i...

It's a bit worrying that they talk about burning human shit to get phosphate when you can just compost it.

The issue is probably all the contaminants in human poo, especially medical: anti-bacterials, hormones, radioactive tracers. Maybe it isn't so much purifying the phosphate that matters, but removing components that would be bad to recirculate into our food chain.

High temperature composting deal with the most common problems anyways, and you preserve the nutrients rather than burn them up. The biggest problem is how bad water waste management systems are at producing fertiziler, the wide spread idea that it's ok to pollute our waste water with what ever, making it unusable for composte is not healthy. I do not think burning it can solve more than a tiny part of that problem.

I guess it's because composting doesn't guarantee the destruction of pathogens.

Yeah human waste fertilizer sounds like a very good way to get outbreaks.

Milorganite is a fertilizer here in the midwest which is kiln dried microbrobes from milwaukee water treatment system,

https://www.milorganite.com/using-milorganite/what-is-milorg...

On the other hand phospor deficiency is easy to come by with smallish amounts of phosporous. Only at hard deficiency the yield will suffer strongly. The nutrient supply-yield curve is very steep in the lower end of supply and shallow in the range of optimal supply. Check Sonneveld et.al.

What I am trying to say is that we sure would like to give optimal supply to out plants, but slight undersupply will still give reasonable yields. Profitability issue? Yes! Problem with feeding the world? Rather not.

We will run out of phosphate soon enough. In the American mid west, the corn and hogs take turns to get the phosphorus cycle going.

When we run out of P, mining asteroids is always an option. How much of a viable realistic option...I don’t know.

I think there are two other viable solutions:

1. Synthesize food in labs using fermentation techniques to feed the world population.

2. Genetically modify Homo sapiens to synthesis food and tinker with metabolism.

Both the above seem more practical and likely feasible than destroying the planet with Ag for marginal benefits.

Phosphorus comprises about 0.1% by mass of the average rock you find walking around, the only thing that’s running out is the extremely high concentrations you find in specific areas.

What we are mining is essentially areas of ocean floor lifted up to the surface. We could also either mine other areas still on the ocean floor that also have high concentrations, or almost anywhere else at lower though still significant concentrations.

I am sure they are due for a regime change for oppressing their people at some point in the future.