TFA: <i>the majority of [phosphorous] reserves are in Morocco/Western Sahara, China, the U.S and South Africa. These four/five countries hold 83 percent of the world’s phosphate reserves according to scientist David Vaccari</i><p>[0] "Ocean engineer David Vaccari says that the most sustainable environmental flow of phosphorus "would be the natural flux: seven million metric tons per year (Mt/yr). To hit that mark yet satisfy our usage of 22 Mt/yr, we would have to recycle or reuse 72 percent of our phosphorus […] The flow could be reduced with existing technologies… [lowering] the loss to waterways from 22 to 8.25 Mt/yr, not very much above the natural flux."<p>[0]: <a href="https://en.wikipedia.org/wiki/Planetary_boundaries#Freshwater" rel="nofollow">https://en.wikipedia.org/wiki/Planetary_boundaries#Freshwate...</a>