# Kaolin & clays: Emissions

Why calcining multiplies kaolin's footprint

Source page: https://www.materialinsights.org/commodities/clays/emissions/

Why calcining multiplies kaolin's footprint What this tab covers The greenhouse-gas footprint of the commodity at a global level, split by lifecycle phase: extraction (or farming), refining and processing, movement, usage, and recycling or end of life. Intensities are per unit of product; the global total combines intensity with world output. Also covers other environmental impacts and the main levers to cut emissions. Emission intensity 0.10 t CO2e per t range 0.01 (crude common clay) to 0.4 (calcined kaolin) · cradle-to-gate; hydrous wet-processed kaolin with spray drying about 0.05-0.2 (derived); calcined clay about 0.2-0.4 (fuel for calcination at 700-850 C plus dehydroxylation water, no process CO2) Global emissions per year 6.00 Mt CO2e per year 2025 · about 0.1 t CO2e/t x 50 Mt kaolin plus about 0.05 x 20 Mt bentonite; excludes common clay for brick

Per 1 t of processed kaolin at plant gate (cradle-to-gate); calcined clay and bentonite noted. Intensity: Indicative, derived; calcination range consistent with LC3 literature (Scrivener et al. 2018). Global total: Derived from USGS MCS 2026.

#### Share of footprint by lifecycle phase
 Extraction 10% Refining / processing 80% Movement 10%

#### Footprint by lifecycle phase

| Phase | Intensity | Share | Main sources of emissions | Notes | Source |
|---|---|---|---|---|---|
| **Extraction** | about 0.005-0.01 t CO2e/t (indicative) | 10% | diesel excavators and trucks in open pits; hydraulic mining in some kaolin pits | Soft deposits need little blasting | Indicative |
| **Refining / processing** | about 0.05-0.15 t CO2e/t for hydrous kaolin; 0.2-0.4 for calcined (indicative) | 80% | degritting, centrifuging, bleaching, filtering, spray or rotary drying; calcining kilns | Drying water out of slurry is the main energy use. Bentonite needs drying from about 30% moisture plus grinding | Indicative; derived |
| **Movement** | about 0.01-0.03 t CO2e/t for ocean shipping (indicative) | 10% | rail and ship for processed kaolin; truck for common clay | Slurry shipping avoids drying but moves water | IMO Fourth GHG Study 2020 (indicative) |
| **Usage** | enabling: LC3 cement with calcined clay cuts cement CO2 by up to about 40% | – | clays are fired in brick and tile kilns, whose fuel use dwarfs clay processing | Fired clay products are about 0.24 t CO2e per t (ICE v2.0, indicative) | Scrivener et al. 2018 (indicative); Hammond and Jones 2011 |
| **Recycling / end of life** | not published | – | kaolin returns via paper recycling; ceramic waste milled into new bodies | USGS: recycling insignificant; EU end-of-life recycling input rate for kaolin 31% | USGS MCS 2026; EU CRM 2023 |

#### Other environmental impacts

Kaolin refining uses large volumes of water and creates sand and mica tailings (Cornwall's white tips). Land use for pits. Silica dust.

#### Levers to cut emissions

- Calcined clay in LC3 cement to replace clinker, cutting cement CO2 by up to about 40% (Scrivener et al. 2018, indicative)
- Mechanical dewatering and waste heat before thermal drying
- Ship slurry rather than drying where buyers can accept it
- Electric or biomass calcining kilns for metakaolin

#### India

India is the largest kaolin producer (8.4 Mt) and second in bentonite (3.7 Mt) in 2025 (USGS), and IIT Delhi and IIT Madras co-developed LC3 cement, which uses calcined clay to cut clinker; Morbi's tile kilns moved from coal gasifiers to natural gas after a 2019 National Green Tribunal order (indicative).
 Emission figures are indicative global averages from the life-cycle studies named; actual footprints vary widely by site, energy mix and method.

## Other sections

- [Summary](https://www.materialinsights.org/commodities/clays/index.md)
- [Overview](https://www.materialinsights.org/commodities/clays/overview/index.md)
- [Correlation](https://www.materialinsights.org/commodities/clays/correlation/index.md)
- [Extraction](https://www.materialinsights.org/commodities/clays/extraction/index.md)
- [Production](https://www.materialinsights.org/commodities/clays/production/index.md)
- [Stocks](https://www.materialinsights.org/commodities/clays/stocks/index.md)
- [Cycles](https://www.materialinsights.org/commodities/clays/cycles/index.md)
- [Trading](https://www.materialinsights.org/commodities/clays/trading/index.md)
- [Movement](https://www.materialinsights.org/commodities/clays/movement/index.md)
- [Criticality](https://www.materialinsights.org/commodities/clays/criticality/index.md)
- [Characteristics](https://www.materialinsights.org/commodities/clays/characteristics/index.md)
- [Relationships](https://www.materialinsights.org/commodities/clays/links/index.md)