Editing Fertilizer (section)

===Phosphate fertilizers===
[[File:Siilinjärvi Särkijärvi pit.jpg|thumb|left|An apatite mine for phosphates in [[Siilinjärvi carbonatite|Siilinjärvi]], Finland]]
Phosphate fertilizers are obtained by extraction from [[phosphate rock]], which contains two principal phosphorus-containing minerals, [[fluorapatite]] Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>F (CFA) and [[hydroxyapatite]] Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>OH. Billions of kg of phosphate rock are mined annually, but the size and quality of the remaining ore is decreasing. These minerals are converted into water-soluble phosphate salts by treatment with [[acid]]s.<ref>{{cite journal |doi=10.1016/j.gloenvcha.2008.10.009 |title=The story of phosphorus: Global food security and food for thought |date=2009 |last1=Cordell |first1=Dana |last2=Drangert |first2=Jan-Olof |last3=White |first3=Stuart |journal=Global Environmental Change |volume=19 |issue=2 |pages=292–305 |bibcode=2009GEC....19..292C |s2cid=1450932 }}</ref> The large production of [[sulfuric acid]] is primarily motivated by this application.<ref>{{Greenwood&Earnshaw2nd}}</ref> In the [[nitrophosphate process]] or Odda process (invented in 1927), phosphate rock with up to a 20% phosphorus (P) content is dissolved with [[nitric acid]] (HNO<sub>3</sub>) to produce a mixture of phosphoric acid (H<sub>3</sub>PO<sub>4</sub>) and [[calcium nitrate]] (Ca(NO<sub>3</sub>)<sub>2</sub>). This mixture can be combined with a potassium fertilizer to produce a ''compound fertilizer'' with the three macronutrients N, P and K in easily dissolved form.<ref name=EFMA2000>{{cite web|last1=EFMA|title=Best available techniques for pollution prevention and control in the European fertilizer industry. Booklet No. 7 of 8: Production of NPK fertilizers by the nitrophosphate route.|url=http://www.fertilizerseurope.com/fileadmin/user_upload/publications/tecnical_publications/guidence_techn_documentation/EFMABATNPKN.pdf|website=fertilizerseurope.com|publisher=European Fertilizer Manufacturers' Association|access-date=28 June 2014|date=2000|archive-url=https://web.archive.org/web/20140729004328/http://www.fertilizerseurope.com/fileadmin/user_upload/publications/tecnical_publications/guidence_techn_documentation/EFMABATNPKN.pdf|archive-date=29 July 2014|url-status=dead}}</ref>