Study finds more aluminium recovered from incinerator bottom ashes

During 2011-2012, the European Aluminium Association (EAA) was actively involved in a significant study at two different Italian incinerators to better understand the behaviour of several aluminum packaging items as they move through the incinerator.

These tests were initiated by the Italian aluminium packaging recovery scheme Consorzio Imballaggi Alluminio (CiAl) and the Polytechnic University of Milan. The results from this Italian project, combined with those of prior experiments in three other West-European countries, have shed some new light on the basic understanding behind the transfer ratios of aluminium from metal packaging to the IBA.

The results of the five tests draw the following conclusions:

· Minimum metal transfer ratios for thin Al foils are at least 40 per cent and for Al cans well above 80 per cent

· Minimum metal transfer ratios for mixed Al packs (from flexible to semi-rigid and rigid) in a typical situation are between 50-75 per cent, depending on the foil share in the mixed aluminium packaging fraction

· The grain (particle) sizes of metallic Al in the IBA varies significantly. This appears to depend on the operational parameters of each plant. Metallic Al was found in all grain sizes, also in the fractions below 5mm and even below 1mm

It has been estimated that, taking 2006 as the reference year, there should still be an average of 2.3 per cent metallic Al in the European bottom ashes. This represents an impressive tonnage of ‘hidden’ aluminium waiting for recovery; equivalent in tonnage to the annual production of a modern smelter!

It is expected that the pressure from new EU waste legislation targeting the phasing out of landfilling, increased recycling and more efficient energy recovery of waste will result in an increase in the volume of waste being processed by WtE incinerators in the next decade. This should result into two to three times more aluminium recovered from bottom ashes by 2020, offering some important economic and environmental benefits to Europe in terms of raw materials saving – provided all Waste-to-energy (WtE) facilities make the relatively small investment to recover it.