Cement
Thermal substitution rate
Also known as TSR, alternative-fuel substitution rate.
Thermal substitution rate (TSR) is the percentage of total kiln energy input supplied by alternative fuels rather than fossil fuel (coal, petcoke, gas, oil). TSR is the headline AFR-adoption metric tracked by the cement industry and is central to every cement-major decarbonisation roadmap.
Typical TSR ranges by region (2025)
| Region | Average TSR |
|---|---|
| Northern Europe (DE, NL, AT) | 60–80% |
| Western Europe (FR, UK, IT, ES) | 40–60% |
| Southern Europe (GR, PT) | 25–40% |
| North America | 15–25% |
| China | 5–10% |
| India | 10–20% |
| Brazil / LATAM | 20–35% |
Several European plants now exceed 90% TSR; the technical and procurement frontier sits beyond 95%.
Why higher TSR drives sonic-horn demand
Each step up in TSR raises the chlorine, sulphur and alkali loading reaching the preheater tower — see sulphur and chloride cycles. This intensifies coating, build-up and pluggage in the preheater, calciner and kiln-inlet, increasing the frequency and severity of cleaning interventions. Sonic horns become more valuable — and often more numerous — as TSR rises.
Related terms
Related terms
- Alternative fuelAlternative fuels (AFR) replace fossil fuel in cement kilns. They cut CO2 emissions and waste-disposal cost but increase chlorine, sulphur and alkali loading in the kiln gas.
- RDF, SRF and TDFRDF (refuse-derived fuel), SRF (solid recovered fuel, higher spec) and TDF (tyre-derived fuel) are the three dominant waste-derived alternative fuels for cement kilns and WtE boilers.
- Sulphur, chloride and alkali cyclesSulphur, chloride and alkali cycles describe how volatile species evaporate from the kiln burning zone, condense in the cooler preheater, and recirculate. Their build-up drives kiln-stop fouling.
- Chloride bypassA chloride bypass extracts a slipstream of kiln gas before the preheater to remove chlorine from the recirculating Cl cycle. Essential at high TSR; the bypass duct itself fouls heavily.