Waste-to-energy and biomass
Municipal solid waste
Also known as MSW, household waste, residual waste.
Municipal solid waste (MSW) is mixed household and commercial waste — the primary fuel for mass-burn waste-to-energy plants. Composition varies daily and seasonally with the source catchment area, weather, recycling rates and economic activity, and that variability translates directly into variable fouling behaviour in the boiler.
Typical composition (mass %)
| Fraction | Approximate share |
|---|---|
| Paper and card | 20–30% |
| Food waste | 15–25% |
| Plastics | 10–15% |
| Wood and garden waste | 5–15% |
| Textiles | 3–7% |
| Glass | 3–8% |
| Metals | 2–5% |
| Inerts / fines | 5–15% |
The plastics fraction is the dominant source of chlorine, the food fraction contributes alkali and moisture, and the inerts pass through as bottom ash.
Composition variability and operations
WtE operators see daily swings of 10–20% in calorific value and 30%+ in chlorine loading. This variability defeats steady-state combustion control and produces episodic low-melt sticky ash events. Active sonic-horn cleaning that can ride through these events without operator intervention is one of the underlying reasons acoustic horns are increasingly the default cleaning specification on new WtE plants.
Related terms
Related terms
- Waste-to-energyWtE plants burn municipal solid waste, RDF, SRF and biomass to generate steam and electricity. Sticky chloride-rich ash defeats conventional cleaning; sonic horns are the dominant fit.
- 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.
- Grate-fired boiler and mass-burn incineratorGrate-fired (mass-burn) WtE boilers burn MSW on a moving grate without fuel pre-processing. The dominant design for municipal waste incineration.
- Low-melt sticky ashLow-melt sticky ash forms when alkali-rich ash particles soften at typical convective-pass temperatures and bond to tube surfaces. Defeats steam sootblowers; primary target for sonic horns.