Kaolin & clays: Emissions
Why calcining multiplies kaolin's footprint
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 brickPer 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.