Keywords

1 Introduction

The construction sector is one of the main contributors, worldwide and, specifically in Europe, to economic growth [1]. However, that growth is still heavily driven by a linear economy, with high consumption of virgin natural resources, where the construction sector is responsible for about 50% of all extracted materials, and about 35% of all waste sent to landfills [2], with materials such as cement and steel, central to the sector, responsible for 14% (about 7% each) of all man-made emissions [3]. Thus, applying circular economy (CE) to the sector, by recovering materials from end-of-life (EoL) buildings, and reapplying them to new construction, the two issues can be tackled: depletion of resources and waste production.

However, the construction sector is unique in the sense that buildings are prototypes; systems and solutions are shared, but the design and onsite construction varies greatly. Also, most buildings have been designed with preoccupations on their construction and maintenance phases disregarding the EoL. The lack of preparation for the EoL makes this stage one of the main hurdles for applying CE principles to the built environment: how to deconstruct unprepared buildings [4].

New methodologies such as Design for Disassembly (DfD) [5] and the proliferation of modular construction will, eventually, change this paradigm [6]. However, today, about 85% of all buildings in the European Union (EU) have been built before 2001 and it’s expected that, in 2050, between 85% to 95% of the buildings built today will still be in use [7]. As buildings are responsible for about 40% of energy consumption in the EU, one of the targets of the European Green Deal is that, by 2050, every building should be a Zero-Energy Building (ZEB) including already built buildings [8], thus, most buildings will need significant interventions in their lifecycle.

2 Methodology

This paper has the main target of exploring how pre-demolition audits, digital platforms and the upskilling of the labour force in the construction sector can, together, bring the circular economy to a widespread application. It is organised by presenting, in the results section, a description of the considered enablers, the main barriers, how those barriers can be surpassed and how each enabler contributes to the adoption of CE as a whole. The results section ends with a vision of how all enablers work together and how CE can be applied to EoL buildings and connected to the design phase.

The work was developed by documental research to identify CE, pre-demolition audits, digital platforms or marketplaces and skilled labour. The aim was to be able to properly define these subjects and link them to their potential role in enabling CE in the construction sector.

The data and information collection took place on ScienceDirect, Scopus, and Google Scholar using the following keywords (isolated, combined, synonyms and acronyms): “Circular Economy”, “deconstruction”, “demolition”, “construction sector”, “audit”, “pre-demolition”, “digital platform”, “marketplace”, “construction demolition waste”, “sustainable”, “barrier”, “opportunity”, “labour”, “upskilling”, “new professions”, “LIDAR”, “photogrammetry”, “radar detection”, “drone”, “automatization”, “BIM”, “scan-to-BIM”, “point cloud”, and “model”. Other sources, namely institutional were also consulted: European Commission Environment [9], EUR-Lex [10], and EEA Grants Portugal Environment [11].

3 Results and Discussion

3.1 Pre-demolition Audits

Deconstruction is not the status quo for several factors, from which, the lack of knowledge about the materials, systems and, as importantly, how to approach deconstruction, are the most relevant [12]. Thus, there is a need for a methodology that can help plan deconstruction: the pre-demolition audits (PreDA).

A PreDA is a systematic evaluation conducted before the demolition or deconstruction of a building or structure. Its methodology involves a comprehensive analysis of the existing building materials, components and systems to assess their condition, value, potential for recovery and environmental impacts [13, 14]. The primary purpose of a PreDA is to inform the stakeholders about the recoverable materials in the building, how to recover them, quantify waste and plan the intervention [15].

Given the importance of applying CE to the construction sector and how the PreDA can be an enabler, especially when applied to the built environment, the European Commission (EC) has developed guidelines for the structure and methodology to apply [16]. The proposed methodology [15] consists of: (i) preliminary research: relevant documentation is collected; (ii) site visit: visit to the site, measurements, and identification of recoverable materials; (iii) inventory: calculation of waste, type and ability to separate, and identification of recoverable materials; (iv) final report: all relevant information is compiled, including the quantities of waste, recoverable materials, plan of deconstruction and waste management recommendations; and (v) quality assurance: validation of the report with the actual data recovered from the deconstruction.

This approach aims to have a standardised report structure, facilitating its reading and interpretation by all interested stakeholders, assuring that all the main points of a PreDA are fulfilled and that the report adds value to the decision-making process and helps the recovery of materials and waste management, enabling the implementation of a CE in the built environment.

However, the development and implementation of PreDAs in the context of a CE, particularly in the construction sector, face several challenges [14], such as lack of building documentation, assuring the correct identification of recoverable materials, time and cost, lack of material marketplaces, lack of skilled labour, among others.

Despite the challenges to the development of PreDAs, several solutions have been proposed to aid, particularly in the data acquisition stage, such as scan-to-BIM, which is a process that involves capturing digital 3D representations of physical spaces or structures using laser scanning technology and then converting the data into a BIM model [17]. It can be used to aid in the development of the PreDA through the creation of a 3D BIM model to assess the building in the study. Scan-to-BIM uses several processes, starting with data acquisition (LIDAR) to capture a point cloud, that is brought into BIM software where it is analysed and converted into a 3D BIM model [18].

Also, it is possible to add another layer of imaging, specifically, photogrammetry, where photographs of the building, are applied to the point cloud gathered, adding visual information to the dimensions gathered from the LIDAR. This step can be used to, more easily, identify materials and, eventually, with the help of machine learning and artificial intelligence [19], automatically identify the building systems, types of connections, types of materials and many other characteristics relevant to PreDAs [20].

For example, Gordon et al. [21] used the Scan-to-BIM methodology with consumer-grade devices, where the auditor used a LIDAR device and took photographs of the relevant areas. Using photogrammetry and point cloud data analysis, was then possible to build a 3D BIM model. At this stage, the level of detail was not ideal, despite being established that the methodology had a reasonable level of success, making possible the construction of a 3D BIM model that was used for the identification of beams.

The challenges identified in the development of PreDAs can be mitigated with the adoption of digital methodologies that create a digital model of the building to be assessed, facilitating measurements and material identification and, with further development, with machine learning and artificial intelligence [19], get to a point where most of the generated wastes are automatically determined, and the recoverable materials, automatically identified. Eventually, in the future, it might be possible to automatically upload the recovered materials into a platform, during the PreDA.

Today, even with little digitalisation, the PreDAs are already central to the transition from demolition to deconstruction. In the future, considering the digitalisation and regulatory efforts, it is to be expected that PreDAs become the status quo when buildings reach the EoL. However, the lack of skilled labour and digital platforms, which are referred to in the following sections, are still important hurdles.

3.2 Digital Platforms

CE not only implicates that the materials are recovered but, most importantly, that they get reused in other buildings. There are already some good examples of this reutilization, such as the projects Upcycle Rows and The Resource Rows, developed in Copenhagen, Denmark [22]. These were designed using materials from EoL buildings, such as an old Carlsberg brewery from which the bricks from the façades were deconstructed in blocks and turned into the façades of the Resource Rows projects.

However, in the named cases, the deconstruction of the buildings used as source took place already knowing that those materials would be used in the projects mentioned, and the deconstruction took place with the needs of the new buildings in mind and according to a pre-determined plan and design.

In situations where this synergy, between deconstruction and new building design, is not possible, digital platforms can be an enabler for CE, especially in the form of online material marketplaces, linking the materials recovered from one site to the design team of a new building or renovation project [23].

One example of these platforms is the C+D platform, developed through EEA Grants. This platform was developed with the target of creating an online platform to facilitate the exchange of CDWs between the producers and the companies that can receive, treat and either set it to landfill or reuse it, being up- or downcycling [24].

The existence of marketplaces is very important; however, there is the issue of what information should be disclosed in the marketplace to characterize the materials.

To the “what information” problem, the answer sits with the material passports (MP). There have been several efforts in creating a standardised document, namely, among others, the proposal made by the BAMB European project [25, 26], the Madaster Material Passport, developed by a private company, Madaster, to inform their material platform [27]; and the Circularity Passport, developed by an EEA grants project between academia and the private sector in Portugal [28].

An MP, despite being useful for new materials, is even more important when trying to implement CE and develop an online material marketplace. The recovered materials need to be characterized in such a way, that the risk of a designer using these recovered materials in a new building is mitigated by the quality of the available information.

Nonetheless, with the recovery of materials and the existence of a platform that allows for their exchange, and with a proper MP with optimized characterisation, there is still the issue of how the designers can use those materials.

The design of a building has almost no limits, i.e. a window can have any dimensions in any material the designers want. The same applies to every other system or material, as almost anything can be made from scratch to fulfil a project’s needs. However, if CE is to be adopted, the design of a new building will need to take into consideration the available materials, limiting the design options. But how can a designer know what is available, or even what will be available when the project passes from the design phase to the construction phase?

These are non-trivial challenges that designers and stakeholders face when wanting to use these materials. A potential solution is the integration of PreDAs with the marketplaces. The general idea is that the auditor identifies the recoverable materials, potentially with help from the scan-to-BIM methodologies [29], and those identified materials can be pre-characterised and immediately uploaded in the marketplace according to the report, naming a date when the materials are made available.

However, there is a need for an intermediary to do refurbishment work and then store the materials until they are needed by the project.

3.3 Skilled Labour

Typically, construction projects have several types of labour, starting at the lowest level of formation, such as bricklayers, to some of the highest, such as engineers and architects [30]. To apply CE to the sector, all of them need upskilling of some sort [31, 32]. Adding to that, creating this new economy will bring the need for new professions in the market, from people with high expertise in deconstructing to experts in data acquisition methods such as LIDAR imaging or drone operators.

Upskilling is fundamental, especially considering the shift from demolition to deconstruction practices. This shift needs a workforce specialized in not just tearing down structures but also in discerning and salvaging valuable materials [33].

Training programs are crucial in equipping workers with these skills and should focus on practical skills for deconstruction, as well as theoretical knowledge about the principles of CE. Additionally, these training initiatives must be accessible and adaptable, catering to the diverse backgrounds of construction workers [33].

The emergence of new professions is a natural progression in this evolving landscape. Roles like deconstruction specialists, material recovery analysts, scanning experts, drone operators, and CE strategists will become increasingly relevant [34]. These professions not only demand a deep understanding of construction materials and processes but also require a mindset shift towards sustainability and resource efficiency. Upskilling for these roles opens new career paths and opportunities for advancement within the industry, contributing to a more sustainable and economically viable future in construction, making it more appealing and inclusive.

For architects and engineers, upskilling involves developing a deepened understanding of sustainable materials, their lifecycle impacts and the consideration of all stages when designing. They’ll need to develop skills in designing buildings that are easier to deconstruct and in selecting materials that can be reused or recycled effectively and are sustainable. This requires a shift in design philosophy, prioritizing modular and flexible constructions that facilitate deconstruction and material recovery at the EoL.

Construction workers, on the other hand, need training in specialized deconstruction techniques. Unlike demolition, deconstruction is a meticulous process that involves carefully dismantling buildings to preserve the integrity of materials for reuse. Skills in material assessment, safe dismantling practices, refurbishment and efficient sorting and storing of recovered materials will become essential.

The upskilling process also involves familiarizing the workforce with new tools and technologies that aid in material recovery and waste tracking. This includes training in the use of digital tools for inventory management and the implementation of BIM systems that can track material usage and facilitate future deconstruction planning.

Overall, upskilling current professions in the construction industry is a critical step toward achieving the goals of CE. By equipping the existing workforce with new skills and knowledge, the industry can make significant strides in reducing waste, conserving resources and, in the end, building a more sustainable future.

3.4 Discussion

The application of CE to the built environment is, as shown, a challenge for everyone involved. Thus, new solutions and paradigm changes are needed. However, the development of new solutions is not enough in itself, as these solutions need to work symbiotically to help the construction sector shift the paradigm from linear to circular.

Figure 1 shows how CE can be applied to the construction sector while showing the main information and material flows and attributing the main enablers of CE to specific stages or tasks within the processes [34, 35].

This system presents a CE approximation to the construction sector, demonstrating the level of complexity in applying it to this sector. It also demonstrates how the identified enablers can help this paradigm shift, from the initial upskilling of the labour force, using technology in the development of the PreDAs to, finally, using a marketplace to exchange the materials.

Fig. 1.
figure 1

(adapted from [34, 35]).

Enabling factors and their application to information and material flows in CE

Full size image

The main idea behind Fig. 1 is that, for the application of CE in the construction sector, two different flows should be considered: an information flow, and a material flow.

The information flow is as follows:

  1. 1.

    During the inventory phase of the PreDA (step 01), the auditor identifies the recoverable materials which can (if chosen) immediately be placed into a marketplace with general information such as materials, characteristics and expected time to be made available, before full characterization.

  2. 2.

    After the deconstruction and the materials are recovered (step 04), the materials are refurbished and fully characterised, creating the MP (step 05) to input into the marketplace (the materials might have been reserved or not).

  3. 3.

    Designers use the marketplace to find suitable materials for the building they’re working on, this process is iterative, and the designers might change the design, so they can use a material, reserve it, and then change the design and revoke the reservation (exchange between steps 06 and 08).

  4. 4.

    In the meantime, the materials are stored either by some intermediary or by any of the stakeholders (step 07).

  5. 5.

    The construction takes place under the final project and uses the materials already defined and, possibly, stored, waiting for use.

The material flow is similar to, and follows the information flow already described:

  1. 1.

    At the deconstruction (step 02), the materials identified on the PreDA are recovered from the building (step 03) with the help of skilled labour.

  2. 2.

    The materials are refurbished and characterised (step 04) by skilled labour.

  3. 3.

    After the refurbishment and full characterization, the materials are stored until use (step 07).

  4. 4.

    Finally, the materials are used as defined by the design, in the project (step 09).

Here, and as already mentioned, PreDA are an enabler through their function of identifying materials, quantifying waste and preparing and planning the deconstruction task. The digital platforms, in the form of marketplaces, are enablers due to the ability to exchange information (and then materials) between stakeholders. And, finally, the need for a specialized workforce, makes upskilling of labour an enabler.

4 Conclusion

This paper has explored the transformative potential of incorporating Circular Economy (CE) principles into the construction industry, with a focus on the End-of-Life (EoL) phase of buildings. The model discussed encompasses pre-demolition audits (PreDA), digital platforms, and the upskilling of labour, presenting a paradigm shift in how we might approach construction and demolition in the future.

PreDAs emerge as central in this model, as they allow for an informed, strategic approach to material recovery, by identifying reusable materials before demolition, making deconstruction possible and attractive.

Digital platforms bridge the gap between recovered materials and new construction projects. These platforms can serve as marketplaces, fostering the flow of recovered materials, essential for the CE in the construction sector.

Furthermore, the importance of skilled labour cannot be overstated. Helping workers to adapt to new construction practices is crucial for the successful implementation of CE principles in the sector. Skilling the workforce will enhance the quality and quantity of material recovered, while also providing a much-needed pathway for sustainable and inclusive employment in the sector.

In conclusion, the integration of CE into the construction industry is not just a theoretical concept but a necessary step towards sustainable development. This approach does not only address environmental concerns but also offers economic and social benefits, setting a blueprint for a sustainable, resilient, and circular construction sector.

The future of the construction industry is one where sustainability is not an afterthought but a foundational principle. The journey towards circular economy to improve sustainability in construction is complex and challenging, but with collaborative efforts, technological innovation, innovative thinking, and full commitment, it is undoubtedly achievable.