## 5 Potential Drivers, Barriers, and Prospects for IBA Use
Raw waste and products thereof may not have the same environmental impact. Thus, testing and requirements to prevent environmental impacts in this context should be considered despite this classification. Moreover, the consequences of this classification in other legislation pieces should be revised, possibly defending the circular economy if proper environmental protection measures can be adopted. In fact, environmental contamination is one of the main concerns when using new materials. Despite the technical feasibility of using IBA in different applications, its environmental performance is still being discussed and is not broadly known. However, some studies in the literature have previously focused on the environmental impacts of some alternatives for IBA management. Using a life cycle assessment (LCA) methodology, [PERSON] et al. [118] evaluated the environmental impacts of different treatment alternatives targeting IBA, namely IBA solidification, IBA recycling in Portland cement production as a substitute for clinker, and for gypsum. A WtE plant from the north of Spain was the site of the case study. The results showed that ash solidification is the least favorable scenario due to the higher consumption of natural resources and emissions, leading to higher impacts on air and water. Among the recycling alternatives, a clinker substitution of 25% was indicated as the best scenario due to the lower consumption of natural resources and environmental burdens, regardless of the distance between the WtE plant and the cement facilities. Nonetheless, the distance had an important influence on the impact on water when decreasing the clinker substitution to 2.5% or substituting the ash for gypsum. [PERSON] et al. [119] also used an LCA to assess the environmental performance of the valorization of IBA to produce steel and aluminum from the recycling of metals and to produce cement. The study showed that the valorization of steel and aluminum recovered from IBA enables great energy savings in the steel and aluminum industries, which are energy-intensive sectors. Moreover, the utilization of IBA to produce cement reduced the consumption of natural resources [90; 119; 120]. [PERSON] et al. [11] provided a literature review regarding the environmental performance of the utilization of IBA in construction-related products. The authors concluded that most of the revised studies favored the analysis of the leachability of the products containing IBA, focusing on the potential heavy metal contamination. Additionally, it was noticed that IBA utilization in the base and subbase layers for road pavement construction is the only IBA application in many countries and for that reason, it is most studied regarding its leaching behavior. It should be mentioned that IBA can be applied in granular form or hydraulically bound. Cement-bound IBA layers will probably have improved environmental behavior since heavy metal mobility during the road lifespan is likely to be limited considering their encapsulation inside the cementitious microstructure. The authors concluded that IBA utilization in road construction is more beneficial than landfilling, but the benefits may not be verified for high amounts of elements released if the leaching behavior of IBA is not properly controlled. With this in mind, the authors suggest that leaching trials must be required and drainage/rainwater collection systems should be considered to deviate water from the IBA-based layers. Moreover, natural weathering/aging prior to IBA utilization is referred to as a form of enhancing the environmental performance of those layers since that process creates a more stable material. Finally, the significant differences in legal frameworks for IBA utilization within Europe contribute to the rather different management frameworks, since each country has its own criteria. A uniform regulatory framework at the EU level may enable IBA utilization as a secondary raw material in compliance with the same high standards of environmental protection in all EU member states.