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119 procedure. To make full use of this strategy, innovative action is needed both in the remanufacturing sector and in city policies.

3. Enhancing reuse in C&D urban processes.

3.1 Reuse strategies in the building sector

3.1.1 The “reuse design project”: features and centre-stage players.

Expansion in urban areas will inevitably accelerate changes in the urban fabric, involving infrastructure, neighbourhoods and public areas, with the goal of providing sustainable city and housing solutions for growing populations. This will lead to different levels of contemporary built environment action, depending on the features of the buildings worked on. Although, in some cases, design strategies such as refurbishment or adaptive reuse will enable the structure and fundamental traits of buildings to be preserved, in many others the original building will require more significant alterations and may even be judged unfit for its new purpose. These latter circumstances will mainly lead to the demolition of existing buildings with new ones being built in their place. In such cases, adopting reuse principles in order to activate SDGs while fostering resource efficiency would appear to be fundamentally important. The effectiveness of such a strategy will have to be supported by urban policies implementing material loops confined to the city boundaries as far as possible and encouraging reuse while preserving city cultural resources.

As Fig. 4 shows, applying reuse processes to a design project requires several interlinked phases, each involving different stakeholders.

Fig. 4 – Phases and stakeholders in a reuse design project.

The first phase in any “reuse design project”– deconstruction - requires an initial survey to obtain adequate knowledge of the building concerned, its materials, products and components and their condition, in order to identify the most suitable strategies to apply. This pre-demolition building audit identifies the material parts workable, at best, for recycling as well as elements suitable

120 for reuse. It is then necessary to choose the most appropriate technologies from those available to

‘mine’ these from the building. While demolition is suitable for portions of the building destined for recycling, efficiently dividing up products and components for reuse requires opting for deconstruction techniques, since these allow elements to be extracted intact. The manual operations required for selective demolition are more expensive as they have to be done by skilled labourers and require longer timeframes, but the potential for selling reclaimed products and components can compensate for the higher stakeholder costs involved. After recyclable materials have been separated out, the elements to be reused are catalogued and stored prior to their use in other construction work.

The second reuse design project phase deals with the potential need to remanufacture the reclaimed elements to enable them to meet the requirements of their ‘second life’. This process originates with a designer’s choices, since products or components can be used for different purposes from their original function and involves the repair and remanufacturing supply chain as well as a performance assessment professional – who may even be the designer him/herself.

EC Directive 2008/98 differentiates between “reuse”, as ‘any operation by which products or components that are not waste are used again for the same purpose for which they were conceived’ and “preparing for re-use”, meaning ‘checking, cleaning or repairing recovery operations, by which products or components of products that have become waste are prepared so that they can be re-used without any other pre-processing’. Whilst, on one hand, this definition widens the spectrum of elements potentially involved in reuse processes, including those considered waste, on the other hand, the precise moment in the life of an object which determines its ‘End of Waste’ (EoW) status is unclear. This legal indecision adds an element of uncertainty to reuse and remanufacturing market performance, exacerbating the lack of demand fostered by mistrust of “second hand” product quality. It is important to point out that, according to the European Construction Product Regulation (European Parliament, 2011), only elements meeting certain performance standards are considered fit for basic construction requirements, whether they are new or otherwise.

The third phase is the use of reclaimed products and components in other buildings: following designer instructions and investor/owner advice, construction companies take care of employing reuse elements in a building.

3.1.2 The “reuse design project”: circumstances and implementation.

This overview of the reuse design project has clarified the role of the various urban stakeholders in the process. It highlights the fundamental importance of the designer’s role in coordinating all the various phases and players, but it also demonstrates that a single architect’s will is not itself sufficient for a successful urban outcome.

For a better understanding of the circular economy’s improvement potential for urban renovation, regeneration and growth, analysing the implementation of the three phases in a building site may be useful. As Fig. 5 shows, this process takes place when a contractor is interested in demolishing a building and promptly reusing its products or components in a new building to be built on the same site. The main difference from a traditional design project is that the reuse purpose entails potentially remanufacturing the elements of the demolished building and storing them on-site: a precise previous plan concerning building site phases and storage management is thus needed.

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Fig. 5 – Comparison between a traditional design project and a reuse design project workflow.

Maximising the resources found in the building itself, this strategy is the simplest application of a reuse process as well as a rare situation. Clearly as it depends on the characteristics of the building to be demolished - the source of the reclaimed elements - this process is moreover defined by designers and contractors. These are, in turn, influenced by their socio-cultural sensitivity and by the market reaction to the reuse design project – understood as both potentially raised costs and the liking and acceptance of buyers. Alongside these planning and decision making elements, the main obstacles in this context are, therefore, those related to legal uncertainties, as described in the previous paragraph.

3.1.3 Closing the loop on a urban level

Improving the outcomes of this process requires broadening its boundaries to encompass a larger area: a neighbourhood, a district, even the whole city. This would allow CE strategies to operate on a different scale, fostering a more self-aware management of CDW as resources in urban governance policies. Urban Mining strategies are based on an in-depth knowledge of the buildings making up a city and aim to close the loop with an awareness of their specific features, materials and textures, thereby contributing to the city’s sustainable development.

As Fig. 6 shows, when enlarged to the urban scale, reuse design projects involve more buildings being demolished which are potentially “material banks”. This represents a further advantage:

the potential for drawing building components from different sources, generating more options and greater flexibility during the design phase of the new building as well as in managing the building site. Moreover, in Urban Mining projects, reuse is not a matter of constructing a new building in the place of a demolished building but can, on the contrary, be replaced with other functions, such as public space roles. Although the larger scale process phases are the same as those of a single building, Urban Mining is a more complex strategy and its advantages are balanced by the obstacles to it: in addition to the legal and stakeholder constraints, the difficulty of this city level process lies in “scouting” reclaimed materials and components. In fact, generally no list of components that can be “mined” in a town exists and hence scouting has to take place at the same time as project conception and design, slowing down the construction process as a whole.

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Fig. 6 – The reuse design project at urban scale.

‘The lengthening of project times’ and the consequent increasing of costs ‘due to the preliminary research phase and to the current uncertainty in the interpretation of waste regulations’

(Altamura & Baiani, 2019) are hence the most significant barriers to the implementation and dissemination of Urban Mining reuse practices in building construction.