Is demolition always selective?
Selective demolition is defined as the combination of operations carried out gradually and in a coordinated way in order to promote the maximum use of the materials that constitute the demolition waste, thus minimizing the fraction destined to landfill.
So, according to the previous definition, it is easy to see that demolition is not always selective. In many demolitions, the prior objective is just to demolish, not to achieve the maximum use of the waste. And, in these cases, waste is generally seen just as a problem to manage.
However, it is obvious that to achieve a circular economy, all the demolitions should be selective.
There is a broad range of materials of different nature that constitute the buildings and construction to demolish. Thus, a construction to be demolished becomes a source of material resources, many of which can be re-joined to the productive cycle, either directly through the reuse of certain construction elements, either indirectly through the corresponding treatment processes.
Having said that, the products coming from the treatment of demolition waste must conform to technical and environmental specifications as a previous step to be used again in construction or industrial applications.
The higher the degree of mixing of the waste, the more compromised will be the technical and environmental viability of the recycled product.
Technically, because the mixture of a material with another of different nature compromises some of the required properties for a certain application.
Environmentally, because the mixture of hazardous waste with non-hazardous waste confers the category of hazardous to the whole with the consequent risk towards the environment and human health.
Therefore, it seems necessary to achieve a greater separation on site of the various material fractions that compound the demolition waste. The traditional demolition process, generator of a single residue without any classification, must evolve towards processes that contemplate a greater separation of materials on-site, which is known as selective demolition.
However, it must be noted that selective demolition entails higher costs. So, a compromise between circular economy criteria and economic aspects has to be reached.
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