Incinerator Bottom Ash Aggregate (IBAA)
The ash resulting from the controlled combustion of waste, Incinerator Bottom Ash (IBA) is frequently only considered in relation to the residue from Residual Waste Incinerators. In this context it represents around 20% of input tonnage and can be produced into a secondary aggregated called Incinerator Bottom Ash Aggregate (IBBA).
Context
The total tonnage of Residual Waste EfW IBA was 6.3 million tonnes in 2024. The total IBA from all other incinerators listed in WikIWaste and referred to in the table was just under 200,000 tonnes in 2024.
Only IBA from Municipal Incinerators[1] (those generally listed as Residual Waste Incinerators in WikIWaste) can be used to produce IBAA if it is non-hazardous in nature.
Guidance on Use of Unbound Incinerator Bottom Ash Aggregate
The original guidance published in 2021 and updated in 2025 (RPS 247) was withdrawn and replaced in May 2026 (RPS 325)[1].
The guidance is designed to limit the risk associated with the leaching of potential pollutants from the IBAA into water courses and underlying groundwater when used in applications such as sub-bases for roads and structural platforms.
