what is IBA?Incinerator bottom ash (IBA) is the non-combustible solid residue left behind after municipal solid waste is burned in waste-to-energy plants, making up about 20-30% of the input waste's weight. Primarily consisting of ash, glass, ceramics, and metal fragments, it is processed to recover metals and often recycled as a secondary aggregate for construction.
A central element of metal recovery is multi-stage sorting. First, non-ferrous metals are separated from the mineral carrier material using a total of 8 powerful STEINERT Eddy current separators. This creates a ZORBA fraction with high metal yield, forming the foundation for downstream fine sorting.
For precise separation within this mixed non-ferrous metal fraction, Greensort XRT sorter – a highly advanced sorting system with X-ray transmission technology (XRT) is employed. Unlike optical systems, XRT recognises the material's interior: light metals such as aluminium or magnesium can be reliably separated from heavier fractions like copper, brass, or zinc based on their atomic density.
In the third sorting step, the recovered non-ferrous heavy metal concentrate is separated by grade using a GREENSORT CHUTEC – a chute sorting system based on a different X-ray technology: X-ray fluorescence (XRF). With XRF, the focus is not on analyzing material density, but rather the elemental composition of individual particles. It is particularly suitable for finest grain sizes down to just 10 mm, as typically occur at this sorting stage. This transforms a complex heavy metal mix into cleanly separated metal fractions such as copper, brass, zinc, or stainless steel – so concentrated and pure that they can be directly returned to industrial material cycles. The recycling loop is complete.
Bottom ash processing poses demanding challenges for sorting systems — residual moisture and corrosive materials require robust solutions. GREENSORT has developed specific adaptations: for example, we uses a fully Zink coating or stainless-steel casing on Eddy separators, effectively protecting them against chemically induced wear from moist materials.