What is waste incineration bottom ash?
Waste incineration bottom ash (IBA) is the residual material that remains after burning municipal and commercial waste in a waste-to-energy plant. After processing and quality checks, this bottom ash is used as a secondary building material, primarily in road construction, earthworks, and civil engineering applications.
Application
Waste-to-energy plants across Europe and beyond process millions of tonnes of waste annually. The bottom ash produced accounts for roughly 20 to 25 percent of the original waste weight, making it the largest by-product of waste incineration.
Processing: After incineration, the raw bottom ash is stored to cool and undergo initial weathering. Ferrous and non-ferrous metals are then recovered for recycling. The remaining material is screened and crushed into an aggregate suitable for use as a building material.
Construction applications:
- Sub-base and base course material in road construction
- Fill material in earthworks and land raising
- Core material in noise barriers and embankments
- Aggregate in concrete (to a limited extent)
Environmental considerations: The use of bottom ash as a building material is regulated by environmental legislation in most countries. The material must meet strict leaching requirements for heavy metals and other contaminants. In the Netherlands, the Soil Quality Decree governs its use; in Germany, the Substitute Building Materials Ordinance (EBV) applies.
By reusing bottom ash as a construction material, primary raw materials such as sand and gravel are conserved, contributing to the circular economy and reducing the volume of waste sent to landfill.
Related terms
- Secondary building material
- Recycled aggregate
- Sub-base
- Circular construction
- Leaching test
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