Expert assessment of the climate protection benefits of IBA

CO₂ ist permanently bound

A study by the Institute for Circular Resource Engineering and Management (CREM) at the Technical University of Hamburg shows that during storage, IBA reacts with CO₂ from the atmosphere – a natural process known as carbonation. The data shows that up to 23 kg of CO₂ are permanently bound per tonne of bottom ash. IBA aggregates are therefore not only a high-quality substitute construction material, but also make a measurable contribution to reducing emissions.

Additional climate benefits through metal recovery

The recovery of ferrous and non-ferrous metals during IBA processing further improves the carbon footprint. The metals separated from the ash replace primary metals, the production of which is extremely energy-intensive. This results in significant CO₂ credits. According to the new expert report, the total CO₂ footprint reches around -205 kg CO₂e per tonne of ash treated.

Compared to mineral raw materials, incinerator bottom ash causes lower emissions during production. While sand and gravel cause 3 to 7 kg CO₂e per tonne, the values for processed IBA range between 2.99 and 4.23 kg CO₂e, depending on the electricity mix – and that is before carbonation is taken into account.

In total, this results in a CO₂ footprint of up to -20 kg CO₂e per tonne, even when the energy required for processing is taken into account. These emission credits enable climate-neutral transport over longer distances without the slag losing its potential as a climate-friendly alternative to primary building materials.