---
title: "Grate-fired boiler / mass-burn incinerator"
description: "A grate-fired boiler (also moving-grate incinerator or mass-burn incinerator) burns mixed municipal solid waste on a slowly moving grate without significant fuel pre-processing. As waste advances along the grate, it dries, ignites, burns out, and finally discharges as bottom ash. Mass-burn is the dominant design for municipal WtE plants worldwide."
canonical_url: "https://sylio.co/glossary/grate-fired-boiler-mass-burn-incinerator"
last_updated: "2026-06-28T02:29:41.525Z"
---

A **grate-fired boiler** (also *moving-grate incinerator* or *mass-burn incinerator*) burns mixed [municipal solid waste](/glossary/municipal-solid-waste) on a slowly moving grate without significant fuel pre-processing. As waste advances along the grate, it dries, ignites, burns out, and finally discharges as [bottom ash](/glossary/incinerator-bottom-ash). Mass-burn is the dominant design for municipal WtE plants worldwide.

## Why mass-burn dominates municipal duty

- Tolerates unprocessed mixed waste
- Simple fuel handling — no shredding or pelletising needed
- Mature, robust, well-supported supply chain
- Established regulatory acceptance under [IED](/glossary/industrial-emissions-directive) and equivalent
- Scales from 50 t/day local plants to 3,000+ t/day urban facilities

## Where fluidised-bed designs compete

[CFB](/glossary/cfb-boiler) and [BFB](/glossary/bfb-boiler) designs compete with mass-burn for specific duties — pre-sorted [RDF/SRF](/glossary/rdf-srf-tdf), sewage sludge co-firing, biomass-only plants. Fluidised beds need more fuel preparation but offer lower NOx and better fuel flexibility.

## Cleaning

Grate-fired WtE boilers benefit from [sonic horns](/glossary/sonic-horn) on the convective pass, ESP/baghouse hoppers and SCR. The fluidised-bed alternatives add cyclone-cleaning duty to the same list.

## Related terms

- [Waste-to-energy](/glossary/waste-to-energy)
- [Municipal solid waste (MSW)](/glossary/municipal-solid-waste)
- [BFB boiler](/glossary/bfb-boiler)
- [CFB boiler](/glossary/cfb-boiler)