Material Insights · Understanding the Material World

Phosphate rock and Phosphoric acid

Phosphoric acid is the step through which almost all mined phosphate reaches fertiliser: rock is dissolved in sulphuric acid, and roughly three tonnes of rock go into each tonne of P2O5. Integrated producers turn most of their rock into acid before it leaves the country, as with over 95% of US-mined rock in 2025, while India imports rock, acid and DAP.

Phosphate rock (commodity) and Phosphoric acid (chemical): 4 relationships.

How they are linked

1. Feedstock

Physical flow · Strong · Phosphate rock to phosphoric acid

In the wet process, the calcium phosphate in rock reacts with sulphuric acid to give phosphoric acid and gypsum, and this is how nearly all phosphoric acid is made.

  • about 2.6 to 3.5 t phosphate rock per tonne of P2O5
  • over 95% of US-mined rock used to make wet-process acid, 2025

The rock needed per tonne depends on its grade: sampled commercial rocks carry about 33 to 39% P2O5, and leaner or more impure rock needs more tonnes and more acid. US producers face lower P2O5 content as reserves deplete. The wet process needs fairly pure rock, so impurities limit which deposits can feed it.

Sources: USGS; EFMA, now Fertilizers Europe (copy hosted by Universidad Politécnica de Madrid); Chemical Engineering

2. Integrated mine-to-acid complexes

Joint production · Strong · Acid made next to the mine or the port

Rock is bulky and acid is the higher-value product, so large producers build acid and fertiliser plants beside their mines or export ports and ship acid or DAP instead of rock.

  • about 25% of US wet-process acid exported, 2025

Integrated producers capture the margin between rock and acid, and US producers export about a quarter of their acid. Importers without rock either buy rock and run their own acid plants, or buy acid and only granulate it into DAP and MAP. The choice decides where the conversion margin and the gypsum waste sit.

Sources: USGS

3. Where rock and acid are made

Geography and ownership · Strong · Rock holders dominate acid supply

Acid plants tend to be built near rock supply, so the largest rock producers are central to acid and fertiliser supply, and Morocco's reserves give it the long-run position.

  • 110 of 250 Mt China's share of world rock output, 2025
  • 36 Mt Morocco rock output, 2025
  • 50 billion t Morocco reserves, the world's largest

China mined about 44% of world rock in 2025. Morocco holds by far the largest reserves, which gives it the long-run position as a supplier of rock, acid and fertiliser. The US, Russia and Jordan are the other large rock producers. India mined only about 1.5 Mt in 2025.

Sources: USGS

4. Price link: product made

Cost and price · Medium · Both ways, with a lag

Rock is the main raw material of acid, but it is often sold on quarterly or annual contracts, so its price follows acid and fertiliser prices with a delay.

  • 0.07 monthly change correlation
  • 0.54 12-month change correlation
  • 1.20 fitted elasticity

Month to month the two barely move together, while over a year they do, with a lag of about five months between the series on the site. Acid prices also respond to sulphur costs, which can move acid without any change in rock.

Sources: Material Insights (World Bank, FRED, IMF data)

For investors

Key learnings

  1. Value in phosphates sits with whoever owns both rock and acid capacity, because integrated producers keep the conversion margin that rock-only or acid-buying firms pay away.
  2. Rock grade matters: falling P2O5 content raises tonnes of rock and acid per tonne of product, squeezing margins of mines with depleting reserves.
  3. Rock is often priced on quarterly or annual contracts, so its price adjusts to acid and fertiliser markets with a delay, which helps acid makers buying rock in a rising market and hurts them when it turns.

What to track

  • Phosphoric acid contract price for India: Sets the benchmark for acid importers and for integrated producers' export margins (Quarterly · industry contract reports, company filings)
  • Phosphate rock price (Morocco): Slow-moving cost floor for non-integrated acid makers (Monthly · World Bank Pink Sheet)
  • China phosphate export quotas: Tighter quotas raise prices for acid and DAP elsewhere (As announced · China customs, industry reports)

For policymakers

Key learnings

  1. India has little rock of its own, so its phosphate security rests on imports and long-term supply deals for rock, acid and finished fertiliser.
  2. Importing rock and making acid at home keeps more value and jobs in India but brings sulphur needs and gypsum waste; importing acid avoids both but leaves less margin.
  3. Stakes in mines and acid plants abroad, and long-term offtake deals, secure supply better than relying on spot purchases when exporters restrict sales.

What to track

  • India imports of rock, phosphoric acid and DAP: Shows the mix between domestic conversion and finished imports (Monthly · Department of Fertilizers, port data)
  • Nutrient-based subsidy rates for P: Changes alter the margin for Indian acid users and DAP makers (Each season · Department of Fertilizers)

India

India mined about 1.5 Mt of rock in 2025 and relies on imports, including about 5.2 Mt of rock from Jordan alone in 2024-25, along with imported phosphoric acid and DAP. Domestic DAP plants run on a mix of imported rock and imported acid.

Sources

  1. Price correlation, Material Insights, Material Insights (World Bank, FRED, IMF data)
  2. Mineral Commodity Summaries 2026: Phosphate rock, USGS (2026)
  3. Best Available Techniques booklet: production of phosphoric acid, EFMA, now Fertilizers Europe (copy hosted by Universidad Politécnica de Madrid) (2000)
  4. New phosphoric acid process expands available resources, Chemical Engineering
  5. Fertilizers: India import report, April 2025, J M Baxi Marine Services (2025)