## 4 Current Management of IBA
This results in the neoformation and hydration of the mineral phases involving carbonation and oxidation reactions, which leads to a pH reduction to the range of 8-10 [55; 57]. The reactions of hydration originate mineral species that can encapsulate some potentially toxic metals, leading to an enhanced leaching behavior [11; 78; 79; 80; 81; 82; 83; 84]. There are several potential applications of IBA. The replacement of aggregates has been an appealing use for IBA due to its geotechnical properties [13]. Many European countries apply IBA as a secondary raw material to replace natural materials (e.g., gravel and sand). Belgium, Denmark, France, Germany, the Netherlands, the United Kingdom, and, in particular, Portugal and Spain use IBA in road construction. IBA has also been applied in acoustic barriers for roads in Germany and the Netherlands [14]. Other common functions involve cement production [40; 85], as aggregate for concrete [14; 40; 86; 87], embarkments [88], and as landfill cover [13; 14]. Furthermore, novel applications have been explored for this material. For example, its use as a precursor for alkali-activated binders, as adsorbent material to remove contaminants from wastewater and landfill gases, and as raw material for the production of ceramic-based products [40; 59; 89; 90]. EU countries have established individual rules with different requirements for the utilization of the mineral fraction of IBA. In this context, appropriate classification of this material can play a key role in future utilization. In the EU, waste incineration is regulated by Directive 2010/75/EU on industrial emissions. This directive sets out that the incineration residues must be recycled as appropriate, and their amount and harmfulness must be minimized. Somewhat conversely, a fraction of IBA is still being landfilled (after a stabilization treatment) in the Iberian countries (Figure 8). However, Portuguese and Spanish IBA has also been used in landfills as a substitute for soil for the intermediate and final cover, construction of paths, accesses, and platforms at the landfill level. The metal recovery for recycling has been continuously carried out in WtE plants from Portugal, amounting to 14,602 kt (mostly ferrous metals) in 2019 (Table 2). Ferrous metals are nearly recovered in total (100%), while only one plant recovers non-ferrous metals (Valorsul) contained in the IBA (around 70%) [44; 91; 92; 93]. In Spain, all the WtE plants are equipped with devices for the recovery of ferrous metals from fresh IBA, amounting to 40.2 kt in 2019 (Table 2), all of it recycled into the steel industry. Furthermore, in Spain, those WtE plants that obtain a conditioned IBA for use as secondary material (TIRME, SIRUSA, UTEEM, TERSA), in addition to continuing to recover ferrous metals through magnetic separators,also recover non-ferrous metals through Eddy current devices, this fraction being around 1-3% of the conditioned IBA [33; 48; 54]. According to [PERSON] et al. (2020) [15], 16 out of 22 EU countries (plus Norway and Switzerland) allow the utilization of mineral IBA outside landfills. However, only 11 of them use it, at a rate varying from 20 to 100 wt.%. These include the Iberian countries under specific requirements (Table 4). In Portugal, mineral IBA utilization outside landfills is permitted and practiced under an individual permit issued by LNEC (_Laboratorio Nacional de Engenharia Civil_--National Civil Engineering Laboratory) to one processing plant (Valorsul). There are no specific parameters defined for Portuguese IBA and total elemental content is not considered. Instead, the requirement is compliance with leaching limit values for Portuguese non-hazardous waste landfill defined in the Portuguese Decree-Law No. 183/2009. Additionally, NP EN 13242:2002 + A1:2010 regulates the use as aggregates for unbound and hydraulically bound materials in road construction and civil engineering work. Currently, Valorsul produces aggregates from IBA in a dedicated plant with a capacity of 200 thousand tons per year.