# Citric acid: Production route

How a mould replaced Italian lemons a century ago

Source page: https://www.materialinsights.org/chemicals/citric_acid/routes/

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.

Almost all citric acid is made by submerged fermentation with Aspergillus niger, a process scaled up by Pfizer in the 1920s and 1930s to replace extraction from Italian lemons (indicative). The routes differ mainly in the sugar source and in how the acid is recovered from the broth. Chinese plants use maize glucose and lime-sulphuric acid recovery at large scale; European and American plants use molasses, glucose or sucrose and increasingly cleaner recovery. Chemical synthesis is possible but uneconomic. Yeast fermentation (Yarrowia) on oils exists at small scale.

#### Routes compared

| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| **Submerged fermentation on maize glucose, lime-sulphuric acid recovery** | most Chinese capacity (indicative) | about 1.1-1.3 t glucose (about 1.8-2 t maize), 0.6-0.8 t lime and 0.7-0.9 t sulphuric acid per t acid (indicative) | 50-300 kt/yr per site in China (indicative) | about 0.8-0.9 t per t sugar against a theoretical 1.07 (indicative) | gypsum about 1 t per t; mycelium and maize co-products sold as feed (indicative) | sugar is roughly half of cash cost; Chinese export prices of about $700-900/t in 2024-2025 suggest cash costs below that (indicative) |
| **Fermentation on molasses or sucrose** | minor share, mainly outside China (indicative) | about 2-2.5 t molasses per t acid (indicative) | 30-150 kt/yr (indicative) | lower and more variable than glucose (indicative) | gypsum, spent mycelium | tracks sugar and molasses prices |
| **Solvent extraction or chromatographic recovery** | growing share in new plants (indicative) | avoids most of the lime and sulphuric acid | retrofit to existing plants | similar | little or no gypsum | higher capex, lower reagent cost (indicative) |
| **Citrates (sodium, potassium, calcium)** | a large share of sales (not published) | about 0.4-0.6 t NaOH per t trisodium citrate (indicative) | integrated with acid plants | near stoichiometric | none material | acid price plus a conversion margin |

#### How each route works
**Submerged fermentation on maize glucose, lime-sulphuric acid recovery**

Starch is liquefied and saccharified to glucose, fermented by A. niger, then the broth is filtered, citrate precipitated with lime, and split with sulphuric acid. The acid is decolourised with carbon, ion-exchanged and crystallised.

Cheapest at scale; gypsum waste and high steam use.
 indicative (basis: textbook process descriptions) **Fermentation on molasses or sucrose**

Beet or cane molasses is treated to remove metals that upset the mould, then fermented. Used by European and Latin American producers such as Jungbunzlauer and Citribel (indicative).

Uses a by-product sugar; more variable broth.
 indicative **Solvent extraction or chromatographic recovery**

Replaces lime and sulphuric acid with an amine solvent or simulated moving-bed chromatography to pull citric acid out of the broth.

Cleaner; costlier to build.
 indicative **Citrates (sodium, potassium, calcium)**

The acid is neutralised with caustic soda, potash or lime to make salts for detergents, food and pharma.

Main detergent form.
 indicative Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.

## Other sections

- [Summary](https://www.materialinsights.org/chemicals/citric_acid/index.md)
- [Overview](https://www.materialinsights.org/chemicals/citric_acid/overview/index.md)
- [Correlation](https://www.materialinsights.org/chemicals/citric_acid/correlation/index.md)
- [Production](https://www.materialinsights.org/chemicals/citric_acid/production/index.md)
- [Feedstocks](https://www.materialinsights.org/chemicals/citric_acid/feedstocks/index.md)
- [Cycles](https://www.materialinsights.org/chemicals/citric_acid/cycles/index.md)
- [Trading](https://www.materialinsights.org/chemicals/citric_acid/trading/index.md)
- [Movement](https://www.materialinsights.org/chemicals/citric_acid/movement/index.md)
- [Regulation](https://www.materialinsights.org/chemicals/citric_acid/regulation/index.md)
- [Characteristics](https://www.materialinsights.org/chemicals/citric_acid/characteristics/index.md)
- [Emissions](https://www.materialinsights.org/chemicals/citric_acid/emissions/index.md)
- [Relationships](https://www.materialinsights.org/chemicals/citric_acid/links/index.md)