Phosphoric acid: Production route
Wet acid for fields, purer acid for food and batteries
What this tab covers How it is made: the main production routes or, for product families, the main product types and technologies, compared on share of supply, inputs per tonne, plant scale, yield, co-products and unit cost.Wet-process acid dominates. Rock is attacked with sulphuric acid and the calcium leaves as gypsum, either as dihydrate (simple, most common) or hemihydrate (stronger acid, less energy). For food, technical and battery uses, wet acid is purified by solvent extraction, or acid is made by burning elemental phosphorus from an electric furnace, which is cleaner but uses far more power. Nitric acid digestion (the nitrophosphate route) avoids gypsum but makes fertiliser directly rather than merchant acid.
Routes compared
| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| Dihydrate wet process | most of world wet-process capacity (indicative, about 80%) | about 3.3 t rock (30-32% P2O5), 2.6-2.8 t H2SO4, steam for evaporation, per t P2O5 (indicative) | trains of 500-1,500 t/day P2O5; Coromandel added a 650 t/day plant at Kakinada | P2O5 recovery about 93-96% (indicative) | phosphogypsum about 4.5-5 t; fluorosilicic acid | at $100/t rock and $400/t acid (2026 levels) feed costs are about $330 + $1,100 per t P2O5 (indicative) |
| Hemihydrate and hemi-dihydrate processes | a minority of capacity, growing in new plants (indicative) | similar rock and acid; less steam (indicative) | 500-1,500 t/day P2O5 (indicative) | about 96-98% (indicative) | cleaner gypsum suitable for building materials | lower energy cost; higher capital (indicative) |
| Purified wet acid (solvent extraction) | a few Mt P2O5 a year (indicative) | about 1.2-1.4 t merchant acid P2O5 per t purified (indicative) | 50-300 kt/yr (indicative) | raffinate goes back to fertiliser | raffinate acid for fertiliser | a premium of several hundred $ per t over merchant acid (indicative) |
| Thermal (furnace) acid | small, mostly China (indicative) | about 13-15 MWh per t of phosphorus (indicative) | small to medium | high purity | slag, ferrophosphorus | power intensive; competitive only with cheap power (indicative) |
How each route works
Dihydrate wet processRock is digested at about 70-80 C, forming gypsum (CaSO4.2H2O) crystals that are filtered on tilting-pan or belt filters. Filter acid of about 26-30% P2O5 is evaporated to 52-54%. It tolerates many rock types and is used by most plants in Morocco, the US, India and China.
Robust and cheap to build; weaker acid needs more evaporation, and the gypsum carries radium and cadmium.
USGS MCS 2026; Coromandel FY26 via phosphate tile; indicative Hemihydrate and hemi-dihydrate processesDigestion at about 90-100 C forms hemihydrate gypsum, giving 40-50% P2O5 acid directly and saving evaporation steam. Recrystallising to dihydrate (HDH) raises recovery to about 98% and gives cleaner gypsum that can be used in plaster or cement.
Better energy and gypsum quality; more demanding operation.
Indicative Purified wet acid (solvent extraction)Merchant-grade acid is cleaned with organic solvents and further steps to remove iron, aluminium, magnesium, fluorine and heavy metals. Output goes to food, technical, electronics and LFP precursor uses. Prayon, Budenheim, ICL and Chinese producers lead.
Much less energy than thermal acid; needs a fertiliser outlet for raffinate.
Indicative Thermal (furnace) acidRock, coke and silica are smelted in an electric furnace to elemental phosphorus, which is burnt and hydrated to very pure acid. China's Yunnan and Guizhou hydropower supports most remaining capacity.
Purest acid; very high energy and emissions on coal power.
Sulfur tile; indicative Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.