Editing Phosphorus (section)

==Production==
===Mining===
[[File:The site of secondary mining of Phosphate rock in Nauru, 2007. Photo- Lorrie Graham (10729889683).jpg|thumb|right|Mining of phosphate rock in [[Nauru]]]]
[[File:ONCF E 1350 with phosphate train near Tamdrost.jpg|thumb|right|A phosphate train on its way to the [[port of Casablanca]] in Morocco.]]

Means of commercial phosphorus production besides mining are few because the [[phosphorus cycle]] does not include significant gas-phase transport.{{r|Neset2011}} The predominant source of phosphorus in modern times is phosphate rock (as opposed to the guano that preceded it).

[[Phosphate mining in the United States|US production of phosphate rock]] peaked in 1980 at 54.4 million metric tons. The United States was the world's largest producer of phosphate rock from at least 1900, up until 2006, when US production was exceeded by that of [[China]]. In 2019, the US produced 10 percent of the world's phosphate rock.{{r|USGS2021}}

===Processing===
Most phosphorus-bearing material is for agriculture fertilisers. In this case where the standards of purity are modest, phosphorus is obtained from phosphate rock by what is called the "wet process." The minerals are treated with sulfuric acid to give [[phosphoric acid]]. Phosphoric acid is then neutralised to give various phosphate salts, which comprise fertilisers. In the wet process, phosphorus does not undergo redox.{{r|Geeson2020}} About five tons of [[phosphogypsum]] waste are generated per ton of phosphoric acid production. Annually, the estimated generation of phosphogypsum worldwide is 100 to 280 Mt.{{r|Tayibi2009}}

For the use of phosphorus in drugs, detergents, and foodstuff, the standards of purity are high, which led to the development of the thermal process. In this process, phosphate minerals are converted to white phosphorus, which can be purified by distillation. The white phosphorus is then oxidised to phosphoric acid and subsequently neutralised with a base to give phosphate salts. The thermal process is conducted in a [[Submerged-arc furnace for phosphorus production|submerged-arc furnace]] which is energy intensive.{{r|Geeson2020}} Presently, about {{convert|1000000|ST|lk=on}} of elemental phosphorus is produced annually. [[Calcium phosphate]] (as [[Phosphorite|phosphate rock]]), mostly mined in Florida and North Africa, can be heated to 1,200–1,500&nbsp;°C with sand, which is mostly {{chem2|SiO2}}, and [[Coke (fuel)|coke]] to produce {{chem2|P4}}. The {{chem2|P4}} product, being volatile, is readily isolated:{{r|Shriver2010}}

:{{chem2|4 Ca5(PO4)3F + 18 SiO2 + 30 C -> 3 P4 + 30 CO + 18 CaSiO3 + 2 CaF2}}
:{{chem2|2 Ca3(PO4)2 + 6 SiO2 + 10 C -> 6 CaSiO3 + 10 CO + P4}}

Side products from the thermal process include [[ferrophosphorus]], a crude form of {{chem2|Fe2P}}, resulting from iron impurities in the mineral precursors. The silicate [[slag]] is a useful construction material. The fluoride is sometimes recovered for use in [[water fluoridation]]. More problematic is a "mud" containing significant amounts of white phosphorus. Production of white phosphorus is conducted in large facilities in part because it is energy intensive. The white phosphorus is transported in molten form. Some major accidents have occurred during transportation.{{r|ERCO}}

===Reserves===
[[File:Global phosphate rock production USGS 1994-2022.png|thumb|Annual global phosphate rock production (megatonnes per yr), 1994–2022 (data from US Geological Survey){{r|USGS2023}}]]

Phosphorus comprises about 0.1% by mass of the [[Earth's crust]].{{r|AGU2007}} However, only concentrated forms collectively referred to as [[phosphate rock]] or phosphorite are exploitable, and are not evenly distributed across the Earth.{{r|Greenwood1997}} Unprocessed phosphate rock has a concentration of 1.7–8.7% phosphorus by mass (4–20% phosphorus pentoxide). The world's total commercial phosphate reserves and resources are estimated in amounts of phosphate rock, which in practice includes over 300 ores of different origin, composition, and phosphate content. "Reserves" refers to the amount assumed recoverable at current market prices and "resources" refers to estimated amounts of such a grade or quality that they have reasonable prospects for economic extraction.{{r|Sutton2013|CIM2010}} Mining is currently the only cost-effective method for the production of phosphorus. Hence, a shortage in rock phosphate or significant price increases might negatively affect the world's [[food security]].{{r|Amundson2015}}

[[File:Global distribution of commercial reserves of rock phosphate USGS 2016; GTK 2015.jpg|thumb|upright 1.3|Global distribution of commercial reserves of rock phosphate in 2016]]
The countries estimated to have the biggest phosphate rock commercial reserves (in billion metric tons) are [[Morocco]] (50), [[China]] (3.2), [[Egypt]] (2.8), [[Algeria]] (2.2), [[Syria]] (1.8), [[Brazil]] (1.6), [[Saudi Arabia]] (1.4), [[South Africa]] (1.4), [[Australia]] (1.1), [[United States]] (1.0), and [[Finland]] (1.0).{{r|Ahokas2015|USGS2023|USGS2025}} Estimates for future production vary significantly depending on modelling and assumptions on extractable volumes, but it is inescapable that future production of phosphate rock will be heavily influenced by Morocco in the foreseeable future.{{r|Walan2014}} According to some researchers, Earth's commercial and affordable phosphorus reserves are expected to be depleted in 50–100 years.{{r|Cordell2009}}

In 2023, the [[United States Geological Survey]] (USGS) estimated that economically extractable phosphate rock reserves worldwide are 72 billion tons, while world mining production in 2022 was 220 million tons.{{r|USGS2023}} Assuming zero growth, the reserves would thus last for around 300 years. This broadly confirms a 2010 [[International Fertilizer Development Center]] (IFDC) report that global reserves would last for several hundred years.{{r|IDFC2010|VanKauwenbergh2010}} Phosphorus reserve figures are intensely debated.{{r|Sutton2013|Cordell2009|VanVuuren2010}} Gilbert suggest that there has been little external verification of the estimate.{{r|Gilbert2009}} A 2014 review concluded that the IFDC report "presents an inflated picture of global reserves, in particular those of Morocco, where largely hypothetical and inferred resources have simply been relabeled “reserves".{{r|Edixhoven2014}}

===Conservation and recycling===
[[File:Yorkshire Water Sewage Treatment Works (Phosphate Removal) - geograph.org.uk - 5979420.jpg|thumb|A phosphate removal sewage treatment station in [[Yorkshire]], England]]

Reducing agricultural runoff and soil erosion can slow the frequency with which farmers have to reapply phosphorus to their fields. Agricultural methods such as [[no-till farming]], [[Terrace (agriculture)|terracing]], [[contour plowing|contour tilling]], and the use of [[windbreak]]s have been shown to reduce the rate of phosphorus depletion from farmland, though do not completely remove the need for periodic fertiliser application. Strips of grassland or forest between arable land and rivers can also greatly reduce losses of phosphate and other nutrients.{{r|Udawatta2011}}

[[Sewage treatment]] plants that have a [[Enhanced biological phosphorus removal|dedicated phosphorus removal step]] produce phosphate-rich [[sewage sludge]] that can then be [[Sewage sludge treatment|treated]] to extract phosphorus from it. This is done by [[incinerating]] the sludge and recovering the resulting ash.{{r|Tweed2009}} Another approach lies into the recovery of phosphorus-rich materials such as [[struvite]] from waste processing plants, which is done by adding magnesium to the waste.{{r|Gilbert2009}} However, the technologies currently in use are not yet cost-effective, given the current price of phosphorus on the world market.{{r|Sartorius2011}}