Dear all,

I am a first year PhD student at the Hong Kong University of Sci & Tech, in Civil & Env Eng. I am trying to model phosphorus in domestic greywater and industry for regions of the world. Briefly, to do that, I use the IFA production statistics of phosphate rocks and fertilizers and subtract the later from the former. Could someone be kind to explain to me what the difference between "phosphate rock" (expressed as P2O5) and "phosphoric acid" (also expressed as P2O5)mean? if the difference represents processing wastes, then what would a negative difference mean? and what would 50% processing wastes mean economically?
The IFA data I am referring to can be found at www.fertilizer.org/ifa/HomePage/STATISTICS/Production-and-trade

Thank you
Best regards

Andre Mbaya

Hi Andre,

phosphate rock is a mineral deposit that is mined. It can be further processed to manufacture fertiliser products, i.e. super phosphate.

phosphoric acid is manufactured.

The phosphorus content of fertilisers is traditionally expressed as P2O5. You can convert from P2O5 equivalents to P equivalents by dividing by 2.3.

Mw[P] = 31 g/mol
Mw[O] = 16 g/mol
Mw[P2O5] = 142 g/mol

1 mol of P2O5 contains 2 mol of P.

1 mol of P2O5 weighs 142g, of which 62g is P. Therefore P2O5 contains 43.71% (w/w) P.

Or in other words

1gram of P is equivalent to 2.3g of P2O5.

But Im not sure if this is the answer you're looking for?

Dear Markh79

Thank you for your reply. In that case, is the difference between phosphate rock and fertiliser (both expressed as metric tonnes of P2O5) equal to processing (manufacturing) waste?

Thank you
kind regards

Hi Andre,

The difference is because they are different products with different phosphorus content.

There is no reference to waste in the link? Can you clarify what you mean by waste?

Mark

Dear Mark,

Thank you for answering my questions thus giving me more insight. A country produces "X" amount of Phosphate Rock (as P2O5) and "Y" amount of fertilizers (as P2O5). Then, what represents the difference between the quantities X and Y i.e. X - Y ? Phosphate which goes to manufacture detergents? or mining losses (e.g. phosphogypsum)? mining wastes?
2. Is it possible to quantify phosphate mining losses? phosphate mining wastes?

Kind regards

Andre