A Study on the Classification of a Mirror Entry in the European List of Waste: Incineration Bottom Ash from Municipal Solid Waste

In the European Union (EU), waste is classified according to the List of Waste (LoW) and relying on the assessment of 15 hazardous properties (HPs). Incineration bottom ash (IBA) from municipal solid waste is a mirror entry in the LoW, which leads to extremely different management options within the EU. IBA has shown potential for different applications under a circular economy perspective, contributing both to avoiding waste landfilling and the consumption of natural resources, such as sand and gravel. In this context, IBA evaluation and classification play a significant role in understanding which protection measures should be taken. This work aims to present an assessment of the 15 HPs and the consequent classification of IBA using data from the industry. Each HP is assessed based on knowledge of waste, chemical composition considering concentration limits for hazardous substances, and/or through tests (chemical, physical, or biological). According to the criteria followed, 5 out of 6 samples from a Portuguese Waste-to-Energy plant were considered non-hazardous. Only one sample was classified as hazardous due to the assignment of HP 10, which resulted from Pb content (0.36%) above the concentration limit established for this property (0.3%). Nonetheless, although most hazardous entries in the LoW have this classification based on HP 14, the results obtained for the samples of this work seem to indicate IBA from this study is non-ecotoxic. Moreover, it has been suggested that IBA could possibly achieve the End-of-Waste status according to the Waste Framework Directive. For such purpose, clear criteria should be laid down to safely use the material, and testing is a crucial step.