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I read that phosphate reserves will exhaust in coming years wiki, why don't we extract it from sewage , is it really that difficult to extract phosphate ?

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    $\begingroup$ Could you clarify what you mean by phosphate going extinct? Phosphates are alive and well and actually a pollution issue to my knowledge. $\endgroup$ – airhuff Jun 2 '17 at 17:20
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    $\begingroup$ It is really difficult to process large volumes of sewage to try and get small quantities of basically anything out of it. Just like there is a fortune of gold dissolved in the ocean, but nobody is going to get rich collecting it. $\endgroup$ – Jon Custer Jun 2 '17 at 18:12
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The idea has been proposed by several journal articles and Wikipedia suggests that it is being done already. In "Phosphate fertilizer from sewage sludge ash (SSA)", Franz proposes a method

whereby more than 90% of phosphorus can be extracted to make an adequate phosphate fertilizer

Also, the journal "Phosphorus recycling in sewage treatment plants with biological phosphorus removal" by Heinzman lists three processes:

  1. Krepo Process
  2. Seaborne Process
  3. Aqua Reci Process

In it Heinzman also mentions that

up to now no phosphorus recycling with a defrayal of costs is possible. The future importance of phosphorus recycling will depend on the market price for raw phosphate, the recycling costs and, furthermore, on the general political framework

So, it appears that it is cheaper to mine it than to recycle it. This may change in the future of course.

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  • $\begingroup$ Phosphate recovery from sewage sludge ash is already past pilot scale. If i recall correctly, a full size plant is currently under construction in northern europe - it was quite a massive EU funded research collaboration. In comparison to franzs method you mentioned, this is a thermochemical process recovering elementary phosphorous (recophos.org). $\endgroup$ – LoschmidtsSchnitzel Jun 22 at 11:47

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