Peak phosphorus - what are the sinks? The minable phosphorus reserves are limited. Where is the mined phosphoprus landing, what are the global phosphorus sinks?

I would assume that most phosphorus is used for fertilizer and ultimately ends up in the water (via consumption by plants, than animals or humans and then wastewater or faeces). The most likely candidate in water would be phosphate ($PO_4^{-3}$). I would assume that phosphate is fixed in microorganisms and that those ultimatly form sediment and get mineralized. But this is a wild guess.

How does the phosphorus cycle actually work after phosphorus is used by humans and emitted into the environment? What are major processes, and in what forms is phosphorus mineralized?
The phosphorous sinks are the ocean and ocean sediments.  

The ocean holds $3 \times 10^{15}$ moles of phosphorous.  

The annual amount of phosphorous input into the ocean, as well as the amount of burial of phosphorous as sediment is on the order of $10^{10}$ moles. 

The sediment is of three categories:


Phosphorous associated with calcium carbonate
Organic phosphorous (associated with organic carbon)
Apatite


See Phosphorous Accumulation in Marine Sediments and the Oceanic Phosphorous Cycle for a detailed analysis.