---
title: "Incinerator bottom ash (IBA)"
description: "Incinerator bottom ash (IBA) is the non-combustible residue discharged from the bottom of a grate-fired WtE boiler. IBA accounts for ~20–25% of the original waste mass and consists of glass, ceramics, metals, fused inorganics and small quantities of unburned organics."
canonical_url: "https://sylio.co/glossary/incinerator-bottom-ash"
last_updated: "2026-06-28T02:29:41.435Z"
---

**Incinerator bottom ash (IBA)** is the non-combustible residue discharged from the bottom of a [grate-fired WtE boiler](/glossary/grate-fired-boiler-mass-burn-incinerator). IBA accounts for ~20–25% of the original waste mass and consists of glass, ceramics, metals, fused inorganics and small quantities of unburned organics.

## Recovery and reuse

IBA is increasingly processed rather than landfilled:

- **Metal recovery** — magnetic and eddy-current separation extracts ferrous and non-ferrous metals (typically 8–12% of IBA mass)
- **Aggregate use** — the processed mineral fraction is used as secondary aggregate in road sub-base, concrete blocks and other applications
- **Landfill** — residual material that fails leaching tests goes to landfill

Distinguish IBA from **APC residue** (air-pollution-control residue), which is the much smaller but more hazardous fraction captured from the flue gas downstream of the boiler.

## Sonic-horn relevance

IBA itself is not a sonic-horn target — it is wet, coarse, and gravity-discharged. The associated bottom-ash conveyors and downstream metal-recovery processing hoppers occasionally benefit from acoustic flow aids.

## Related terms

- [Waste-to-energy](/glossary/waste-to-energy)
- [Grate-fired boiler / mass-burn incinerator](/glossary/grate-fired-boiler-mass-burn-incinerator)
- [APC residue](/glossary/apc-residue)