Circular economy and blockchain-integrated road map to improve construction waste management Open Access

Waste generation has become a severe problem all over the world due to the intense growth in urbanisation and industrialisation (Amudjie et al., 2023). It is anticipated that the annual waste generation in 2025 will reach 2.2 billion tons and it depicts the gravity of this prevailing issue (Usmani et al., 2020). Among the largest industries that significantly contribute to the global economy, the construction industry is well known for its excessive resource consumption and the corresponding waste generation (Munaro and Tavares, 2023). A major reason behind the excessive waste generation in the construction industry is argued as the industry’s direct connection with the perpetual growth of population and urbanisation (Kabirifar et al., 2020). Approximately, half to three-quarters of construction materials are delivered as waste to the environment per year from the inputs that are used in construction projects (Benachio et al., 2020). As a solution, sustainable WM has been used in the construction industry over the years to mitigate excessive waste generation (Hasheminasab et al., 2022).

Among the available sustainable WM concepts, CE is considered an important, modern sustainable concept that can be used to optimise WM in the construction industry (Norouzi et al., 2021). In addition, the CE concept can be integrated with the waste hierarchy index that prioritises waste reduction, reuse and recycling to enhance the efficiency and effectiveness of the WM process (Ayçin and Kayapinar Kaya, 2021). However, several factors including supply chain issues, technological boundaries and poor cross-industrial collaborations have negatively impacted the successful adaptation of the CE principles in the construction industry (Springvloed, 2021). Besides, the different priorities in the construction industry have become a major complication in CE policy development (Eze et al., 2024). The stringent resistance to change, the complexity of the products and least digitalisation of the construction industry also act as major barriers to a successful transition to a circular built environment (Springvloed, 2021). Nonetheless, in overcoming the major environmental impact of construction waste, it is of utmost importance for the construction industry to transfer towards a circular production and consumption pattern by overcoming the challenges that hinder the successful transition to a circular built environment (Atapattu et al., 2024).

Meanwhile, BC technology has been adopted globally for WM systems since BC provides a unified and single platform where data can be shared in a verifiable, secure, effective and transparent manner (Ahmad et al., 2021). BC is a decentralised network where auditability, persistency and anonymity are the main characteristics and provide maximum cost savings and high efficiency without the involvement of a third party in monitoring the system (Khuc et al., 2024). All the activities that have been done in each step of the BC are stored in a block and linked with the updated block in the system, which provides opportunities to identify the responsible person for each activity and mitigate discrepancies (Upadhyay et al., 2021). In the construction industry, BC has been adopted to mitigate discrepancies that occur due to non-specified drawing editing, and drawing handling even with the use of building information modelling (Li et al., 2019).

Given these merits, BC technology has been identified as a modern economic drive in many industries all over the world (Chaudhary et al., 2021). According to Khuc et al. (2024), BC technology accelerates the effectiveness of sustainable decision-making. Importantly, BC-based approaches such as Swachhcoin, Recereum and Plastic Bank are being adopted in the modern world to increase the productivity of the WM process (Gopalakrishnan and Ramaguru, 2019). Specifically, BC has been identified as a social technology or a tool for collaboration in the context of CE because, it aids in the connection and coordination of several distributed databases, all of which can be updated at the same time and are visible to all stakeholders (Upadhyay et al., 2021). At the same time, BC allows the collaboration between waste suppliers, deconstruction contractors and material recovery facilities which helps to manage excessive waste generations (Rodrigo et al., 2020). There are certain important features of BC that are either lacking or have very limited functionality in a traditional information system (Perera et al., 2020). For instance, BC is transparent, secure and auditable due to its strong accountability and it also makes it possible to trace and track waste safely and securely (Rodrigo et al., 2020). In other words, compared to traditional information systems, BC simplifies observing how the various categories interact and complement one another in the transition to a circular economy (CE) focused on waste reduction (Li et al., 2019). Specifically, researchers and practitioners worldwide are investigating numerous possibilities for promoting sustainable waste management (WM) through BC technology since BC is considered an appealing technology in the WM sector (Jiang et al., 2023).

Past research studies have relied on the integration of BC and WM (Chaudhary et al., 2021; Neha and Punam, 2018), and the integration of CE and WM (Priyadarshini and Abhilash, 2020; Salmenperä et al., 2021; Tomić and Schneider, 2020) and the integration of CE and BC (Alexandris et al., 2018; Ferreira et al., 2023; Yildizbasi, 2021). However, there is a dearth of literature on the integration of BC and CE towards optimising WM in the construction sector. Yet, the effective implementation of CE principles is considered crucial in overcoming the prevailing WM issues in construction (Munaro and Tavares, 2023) and the intervention of novel technologies such as BC is considered essential in prevailing over the challenges that hinder the successful transition to a CE (Upadhyay et al., 2021). Therefore, examining the synergy of BC and CE to improve WM in construction is crucial to uncover creative solutions that can enhance productivity, optimise resource consumption and create a more resilient and sustainable construction industry (N. Rodrigo et al., 2024). Therefore, this study aims to investigate the potential of converging BC with CE to improve construction waste management (CWM). In attending to this aim, the below objectives are put forward to (i) identify the notable practices of CWM that can be improved by the convergence of blockchain (BC) with CE, (ii) investigate the methods to converge BC with CE to improve each notable practice of CWM, (iii) investigate the enablers of the convergence of BC with CE to improve notable practices of CWM and (iv) investigate the barriers to the convergence of BC with CE to improve notable practices of CWM.

This study consists of a comprehensive literature review in Section 2 and the research method is presented in Section 3. Followingly, Section 4 provides the analysis of the collected data and Section 5 discusses and matches the patterns of primary and secondary data. Section 6 summarises the conclusions, recommendations, implications and limitations of the study.

CWM is identified as a complex adaptive system where a complete comprehension of each component does not necessarily translate into a complete understanding of the behaviour of the entire system (Aksel and Cetiner, 2020). Currently, CWM has become a global concern, and many industrialised nations have acted to improve the sustainability of CWM (Kabirifar et al., 2020). Sustainable CWM practices mainly include reducing, reusing, recycling and recovering (Amudjie et al., 2023), however, disposal, landfill and treatment for hazardous waste are among the most common CWM practices (Aksel and Cetiner, 2020). Furthermore, incineration, waste transportation, burying, collection, composting, source reduction and avoidance can be identified as the other available CWM practices (Aksel and Cetiner, 2020). While composting has historically been related to the management of organic waste, it can also be used in the construction industry for soil stabilisation and erosion control, demonstrating its potential for fostering sustainable industry practices (Razak Al-Ani et al., 2016; van der Kamp et al., 2018). Nonetheless, Kabirifar et al. (2020) stated that the majority of the CWM practices are conventional methods. Therefore, a high tendency is perceived among researchers and professionals in finding novel CWM practices. In this sense, modern technologies have been used to improve the efficiency and effectiveness of the CWM process (Norouzi et al., 2021), majorly including the CE concept and BC technology.

With the understanding of the finite availability of resources, the creation of a circular and proactive approach is considered a key requirement in sustainable resource management (Hasheminasab et al., 2022). Consequently, CE has been introduced as a new sustainability principle that can successfully replace the linear economy model of the infinite resource concept (Eze et al., 2024). The CE concept places emphasis on creating items in a reusable form, recycling and zero waste implementations with the goal of minimising the consumption of natural resources and reaping financial gains from them (Ayçin and Kayapinar Kaya, 2021). Specifically, the developing paradigm of CE enforces a low-carbon and less-polluting economy while optimising the existing patterns of environmental management (Priyadarshini and Abhilash, 2020). Eventually, Salmenperä et al. (2021) argued that the transition to a CE will notably improve the efficiency and effectiveness of existing WM practices.

BC technology is one of the best techniques that can be adapted in WM in a persistent way as BC stores data in a connected series of blocks, making it simple to identify changes by computing the hash of one block and comparing it to the hash recorded in the next block (Taylor et al., 2020). Authors further stated that BC is currently applied in WM within payment facilitation, and waste tracking and monitoring. According to Gopalakrishnan and Ramaguru (2019), there are more BC-based applications that are being currently used such as Swachhcoin (BC-based strategy for efficient and environmentally friendly micromanagement of trash, primarily from homes and businesses and turning them into usable goods), Recereum (BC-based platform for recycling waste and generating actual value from it) and Plastic Bank (BC-based program that seeks to monetise users while halting the flow of garbage into the ocean). Moreover, BC can be used in a cloud-based environment to increase the security of the WM system which encourages people to actively participate in the WM process through their smartphones and personal computers (França et al., 2020). Furthermore, Joshi et al. (2022) revealed that BC provides solutions for problem areas named, fraud and manipulation, wrong/loss of information, manual processes and low knowledge and control that arise in WM practices.

Simultaneously, BC technology can assist the CE concept through information management (Kouhizadeh et al., 2019). In another aspect, the upgraded combination of BC and CE will accelerate the establishment of the green BC which provides and secures circular sustainability (Hatzivasilis et al., 2021). In this sense, studies suggest that the challenges peculiar to the CE transition can be overcome by the successful incorporation of the distinct characteristics of BC technology (Ferreira et al., 2023).

BC technology serves WM by providing unified and single platforms for data management (Ahmad et al., 2021), and with the collaborative characteristics of BC technology, the implementation of the CE concept can also be accelerated (Kouhizadeh et al., 2019). Accordingly, the potential of integrating BC with CE in improving the CWM can be further comprehended by the available integration methods that are relevant to the construction context and also by understanding the enablers and barriers for integration in a common platform.

In enhancing the effectiveness of the WM processes, there are several methods followed for the integration of BC and WM including the Swachhcoin approach, Ethereum’s BC Public Network Architecture Platform and the Cloud computing environment (França et al., 2020). The Swachhcoin approach is a BC-based solution for micromanaging garbage, largely from families and companies and transforming them into valuable products in an efficient and environmentally responsible manner (Gopalakrishnan and Ramaguru, 2019). In Ethereum’s BC Public Network Architecture Platform, a peer-to-peer network is created for the secure execution of smart contracts that are highly required for an efficient WM process (França et al., 2020). On the other hand, a cloud computing environment provides the storage and access of computing services via the Internet rather than traditional hard drives which optimises the mechanisms of WM (Velazquez, 2022).

The other available methods for the integration of BC into WM processes include the Recereum platform, Plastic Bank concept, CE–Internet of Things (IoT) BC with DanKu protocol and SaaS (Software as a Service) platform (Kurtulmus and Daniel, 2022; Salesforce, 2022). The Recereum platform is a BC network that converts waste and recyclables into cash while allowing a direct connection between individual users and garbage collection organisations (Gopalakrishnan and Ramaguru, 2019). The authors further explain that the Plastic Bank concept is a BC-based service that monetises people to reduce the flow of plastic into the ocean. In addition, in CE–IoT BC with DanKu protocol, the DanKu protocol makes use of BC technology through smart contracts which enhances the efficiency of WM practices (Kurtulmus and Daniel, 2022). Moreover, the SaaS platform provides software that is relevant to WM as a service via the Internet (Salesforce, 2022).

Even if existing studies lack investigations on the possibilities of integrating BC with CE to improve CWM, plenty of studies have separately focused on the enablers and barriers for the integration of CE and WM (Ezeudu et al., 2021; Mahpour, 2018), BC and WM (Lenz and Tsangaratos, 2022; Sahoo et al., 2021) and CE and BC (Kouhizadeh et al., 2019; Şahin, 2023; Yildizbasi, 2021). Eventually, the enablers and barriers that are common for at least two integrations are depicted in Table 1 of the study.

As Table 1 explains, increased publicity for the organisation, new investors, increased job opportunities, cost-saving methods and improved sustainability are common enablers for all three integrations and the other enablers are common for only two of the integrations from CE and WM, BC and WM and CE and BC. On the other hand, low knowledge and experience, high complexity, insufficient accessibility to data, resistance to change and low regulatory support and practice are the barriers that are common for all three integrations of CE and WM, BC and WM and CE and BC. Specifically, Fedotkina et al. (2019) state that organisational activities and state support measures can be conducted to overcome such barriers. More importantly, it is crucial to immediately implement proper strategic measures of CWM to overcome the unsustainable waste generation patterns of the construction industry, which directly affects the ecological balance of nature (Gopalakrishnan and Ramaguru, 2019).

The construction industry is the backbone of a country’s economy (Eze et al., 2024), yet it accounts for more than 30% of natural resource extraction and 25% of global solid waste generation (Benachio et al., 2020). Due to the world’s ongoing expansion and urbanisation, construction and design activities generate a massive volume of construction waste (Kabirifar et al., 2020). Therefore, sustainable WM is adopted in the construction industry to reduce waste generation and the industry has focused on using CE principles to overcome the futile WM practices in the linear economy (Benachio et al., 2020). When the CE concept was adapted for WM, the effectiveness and productivity of WM processes and practices were increased (Salmenperä et al., 2021). Therefore, with the help of the waste hierarchy index, CE can be used to improve CWM (Norouzi et al., 2021).

In the chorus, the effectiveness of the CE concept also can be improved with the help of other technologies and BC technology is the one of best technologies that can be adapted to enhance the effectiveness of CE activities (Kouhizadeh et al., 2019). Notably, there are many barriers to the effective implementation of CE principles in the construction industry including poor cross-industrial collaborations and the least digitalisation (Springvloed, 2021), which can be overcome by the effective integration of BC technology (Ferreira et al., 2023). Simultaneously, many studies have focused on the effective implementation of BC in the construction sector (Li et al., 2019; Qian and Papadonikolaki, 2021), incorporation of BC for WM (França et al., 2020; Gopalakrishnan and Ramaguru, 2019; Lenz and Tsangaratos, 2022; Sahoo et al., 2021) and the effective integration of BC with CE (Alexandris et al., 2018; Hatzivasilis et al., 2021; Kouhizadeh et al., 2019; Upadhyay et al., 2021; Yildizbasi, 2021). Furthermore, to comprehend the current research status of the fields of BC, CE and CWM, a gap analysis has been conducted by selecting the research articles in the field. The articles were searched in the Web of Science (WoS) database using the keyword string, blockchain AND “circular economy” AND (“waste management” OR waste) AND (construction OR “built environment” OR “building industry”) and 20 results were received. After screening the abstracts, 12 papers were selected considering their relevance to the research field and the selected papers are listed in Table 2 of the study.

As denoted by Table 2, there are several studies that have been conducted related to the fields of BC, CE and CWM. The potential of using BC technology to enhance CE principles in managing construction waste has been mentioned by many of these selected studies (Elghaish et al., 2022; Eze et al., 2024; Liu et al., 2022; N. Rodrigo et al., 2024; L. Wu et al., 2023; Z. Wu et al., 2024; Yuan et al., 2024). However, none of these studies have investigated the consensus opinions of industry experts on how to converge BC and CE to improve CWM. Therefore, it is vital to address the literature gap on the integration of these three concepts as it will assist industry practitioners in comprehending BC-enabled CE applications that will enhance CWM. Eventually, it is significant to accelerate the transition to a circular built environment, since it will cease the disastrous construction mechanisms and contribute to a development where resources are used in a more responsible and sustainable manner (Sharma et al., 2022).

Based on the exploratory nature of this study, a qualitative approach has been used since the qualitative approach derives in-depth conclusions to the research questions based on people’s views and experiences (Crossman, 2020). Besides, this study addresses the question of “how BC can be integrated with CE to improve CWM”, thus, needs expert views and opinions to fill this unaddressed gap in the literature. Accordingly, a qualitative approach has been followed since it allows comprehension of detailed and in-depth knowledge related to unaddressed gaps in existing studies (Rosenthal, 2016).

Qualitative Delphi surveys allow reaching consensus through regulated feedback iterations and it is a highly reliable method to draw conclusions with more credibility (Belton et al., 2021). A Delphi survey consists of more than one round where the consensus feedback for the previous rounds will be shared with the same expert panel prior to the subsequent rounds and the number of rounds will be decided when the Delphi expert panel reach a mutual agreement on the research question (Barrios et al., 2021). It is difficult to guarantee unbiased feedback in traditional interviews, which usually involve only one round of expert input, since participants are not given the opportunity to review and refine their answers (Ahmadi et al., 2023; Winkler and Moser, 2016). Delphi studies, on the other hand, use iterative rounds with progressing questions, which reduces individual biases and improves the reliability of the responses with inbuilt validation of the survey instrument (Ahmadi et al., 2023; Boesl et al., 2017; Winkler and Moser, 2016). Similarly, it is rather difficult to ensure unbiased feedback in focus groups since anonymity cannot be maintained and participants may be influenced by the presence of others (Boesl et al., 2017; Winkler and Moser, 2016). Therefore, this study consisted of three Delphi rounds and data were collected through semi-structured expert interviews to gather more descriptive and reliable data with unbiased and collective opinions (George, 2022). Semi-structured interviews were selected as the data collection technique for the Delphi survey since it allows open-ended discussions related to the research area while also maintaining the focus on the study (Adeoye-Olatunde and Olenik, 2021). Each Delphi round consisted of several phases which allowed systematic collection of data related to the research question and are listed in Table 3 of the study.

Accordingly, semi-structured interviews were conducted in three rounds and feedback from each round was shared among the Delphi expert panel during the subsequent round, where the experts were allowed to review their opinions against the consensus and provide regulated feedback. Besides, as indicated in Table 3, 18 experts were selected as the Delphi expert panel since previous studies suggested that Delphi panels of 19 participants or fewer have no evidence of data overloading and provide accurate and informative conclusions on the research question (Belton et al., 2021). On the other hand, achieving data saturation towards the completion of 16–18 interviews resulted in deciding the number of experts for this study.

The expertise and the heterogeneity of the participants have a direct impact on the credibility and accuracy of the data collected from Delphi surveys, thus, the non-probability purposive sampling method with pre-defined expert selection criteria is highly recommended for qualitative survey studies (Campbell et al., 2020). Accordingly, this study adopted criteria as relevant to the research question and a heterogeneous sample was selected within different countries, levels of experience and professional backgrounds. The study’s expert selection criteria with the profile of the experts and their participation in the Delphi rounds are also presented in Table 3 of the study. As Table 3 suggests, with the 18 experts who fulfilled the selection criteria, 51 semi-structured interviews were conducted in total, respectively 18, 17 and 16 interviews for the three Delphi rounds. Each interview was directed for approximately 60–75 min and conducted face-to-face with the experts. The interviews were audio recorded and transcribed to text before the analysis of data.

Content analysis sharpens attention on the data set and lessens distraction from the method rather than the data’s context (Williams, 2022). Content analysis with manual coding was used to analyse the collected data from the empirical study since content analysis is one of the most popular approaches for analysing qualitative data (Kyngäs, 2020). Following Williams and Moser (2019), the coding process in this study was carried out in three steps, i.e. open coding (developing conceptual categories), axial coding (identifying relationships between open codes) and selective coding (selecting the focal core codes). By selecting and classifying important data from the interview transcripts, open coding made it possible to create a preliminary framework to achieve the aim of the study. The links between these data were further emphasised via axial coding, which provided insight into the ways in which BC technology and the concepts of the CE cooperate with regard to CWM. To ensure that the final framework reflects the noteworthy CWM practices, enablers and barriers, selective coding was used to refine and prioritise the essential themes that are consistent with the aim of the study. Furthermore, during the analysis, ≥75% was used as the acceptable cut-off to identify the expert consensus on findings since a similar method has been followed in past studies to identify the expert consensus on the outcomes (Barrios et al., 2021).

Following the content analysis, data validation is conducted in qualitative research to increase the accuracy, transparency and integrity of the findings (Ningi, 2022). Generally, data validation is performed with a key informant sample of a smaller number of experts who are actively involved in the particular research area (Kapanen et al., 2021). Accordingly, four semi-structured interviews were conducted with experts who are actively engaged in BC and CWM with direct exposure to CE in construction and the four experts include; (i) a Lecturer in built environment with 8 years of experience and a strong research background in CE, BC and CWM, (ii) a Lecturer in quantity surveying with 5 years of experience and a strong background in CE and BC, (iii) a Contract Manager with 18 years of experience in the construction sector and a strong background in CE and BC and (iv) a Director in a construction firm which provides services in quantity surveying related software with 31 years of experience in the construction sector and a strong background in CE, BC and CWM. Eventually, the findings of the Delphi expert survey were refined and validated to arrive at a definitive conclusion on the integration of BC with CE to enhance WM in the construction industry.

Accordingly, the overall research process is illustrated in Figure 1 of the study.

As Figure 1 indicates and as explained in this section of the study, a sequential research process with a qualitative approach was followed to address the research question of this study.

According to the literature findings, 14 WM practices were identified which were consensually accepted as CWM practices by all the experts during Delphi Round 1, Phase 1. In addition, three CWM practices were suggested by the Delphi experts which are indicated in bold text in Table 4. Followingly, all these 17 practices were brought forward to Delphi Round 2 where expert opinion on the notable CWM practices that can be improved by the convergence of BC with CE was assessed. Accordingly, only eight CWM practices received ≥75% positive consensus from the Delphi experts as significant CWM practices which can be improved by the integration of BC with CE which are presented in Table 4 of the study.

As Table 4 explains, nine CWM practices were rejected since they did not achieve ≥75% positive consensus for the notability related to the convergence of BC with CE in improving CWM. Experts suggested that practices such as landfilling (23.53%), disposal (17.65%), incineration (47.06%) and burying (0%) are ineffective linear WM strategies that will eventually cause numerous issues in the upcoming future. Similarly, waste transportation (70.59%) and treatment of hazardous waste (58.82%) were also considered by the experts as ineffective WM practices since they involve the utilisation of other resources including fossil fuel. Furthermore, reducing (64.71%), source reduction (64.71%) and avoiding (47.06%) were rejected by the experts since the involvement of BC characteristics does not have a considerable impact on material-reducing practices.

Conversely, recycling and recovering were accepted by all the experts since it was claimed that the involvement of BC-enabled CE principles would remarkably improve the efficiency of these CWM practices. Furthermore, collecting, redistributing, purchasing sustainable materials, returning/reselling excess/surplus materials, reusing and composting were also consensually accepted by the experts as CWM practices that have a higher potential to be improved with the integration of BC technology and CE principles.

The literature findings indicated seven methods that can be adapted to improve WM using BC and CE and in Delphi Round 1, experts consensually acknowledged that these seven methods are suitable for improving CWM. In addition, two methods were introduced by the experts i.e. BC for waste trading and CircularChain which are indicated in bold text in Table 4. Experts suggested that BC for waste trading is a collaborative platform that connects providers who can supply waste and receivers who can buy waste and CircularChain is a combination of CE and BC which helps to produce secondary raw material in a sustainable way. Eventually, all these nine integration methods received ≥75% positive consensus from the Delphi experts. Accordingly, they were brought forward to the Delphi Round 3 to identify their applicability to each notable CWM practice and these results are also presented in Table 4 of the study. As Table 4 suggests, recycling practices can be significantly improved by integrating BC for waste trading and experts suggest that integration of this method will complete the complex middle stages of the recycling process more efficiently. Furthermore, the plastic bank concept can be used to optimise CWM practices such as recycling, collecting, redistributing and reusing, yet experts suggest that this concept cannot be used with CWM practices such as composting, which involves organic waste and surplus materials.

Experts explained that Ethereum’s BC platform can be used to identify the excess material, which cannot be used for its original purpose and that eventually paves the way to more effective recovery practices in construction. Furthermore, when CE–IoT BC with DanKu protocol is used in waste collection practices, sensors can be used in waste collection bins to improve the collection process so that waste collectors can easily be aware when bins are filled. Besides, according to the experts, redistribution of construction waste can be optimised using Ethereum’s BC platforms since it will improve the identification of excess material and usage of materials. Moreover, Delphi findings suggest that CircularChain will enhance the connectivity of sustainable material purchasing processes which is highly essential for the productivity of its procurement.

In Delphi Round 2, experts were presented with the 25 enablers that were discovered from existing literature (presented inTable 1in sub-section 2.2.2) and questioned on their relevancy in the integration of BC with CE to improve CWM. Accordingly, eight enablers received less than 75% consensus from the experts (i.e. revealing new revenue streams, publicity for the organisation, new investors, reverse logistic improvement, cost saving method, way to new trading networks, increased use of new technologies and pre-existing policies). Concurrently, 17 enablers received ≥75% positive consensus from the Delphi experts. In addition, three enablers were suggested by the experts which include (i) introducing certification methods, (ii) removal of third parties and (iii) digital literacy. These additional enablers also received ≥75% positive consensus from the Delphi experts, thus, 20 enablers were brought forward to Delphi Round 3 of the study. In Delphi Round 3, experts were asked to identify the applicability of each enabler to each of the notable CWM practices and the enablers that received ≥75% positive consensus for each notable CWM are indicated in Table 5 of the study.

According to Table 5, it is evident that enablers such as immutable auditing facility, transparency, trackability and traceability are common for most of the notable CWM practices and experts reasoned that the integration of BC with CE reduces the errors of the process which will eventually earn the trust of the users. Furthermore, the removal of third-party involvement and high efficiency are also considered enablers for most of the CWM practices since the incorporation of BC-enabled CE benefits the stakeholders by reducing the time consumed for the CWM processes with minimal involvement of external parties. Specifically, in experts’ opinion creating job opportunities and increasing sustainability is also applicable for most of the CWM practices since there are numerous procurement systems that revolve around these notable CWM practices and integrating BC with CE to improve these practices will create new revenue streams and will significantly serve to the establishment of a sustainable construction industry.

Literature findings revealed 27 barriers to the integration of BC, CE and WM (presented inTable 1in sub-section 2.2.2) and these barriers were presented to the experts during Delphi Round 2 to gather their views of the applicability of these barriers to the integration of BC with CE to improve CWM. Accordingly, eight barriers received less than 75% consensus from the experts (i.e. Cultural differences, difficulties in selecting the correct person for incentivisation, high cost of data storing and processing, complications in fixing incorrect data, interoperability issues, lack of goals, low number of literature, inability to identify the ownership of the person who is responsible for waste in the chain). At the same time, 19 barriers received ≥75% positive consensus from the Delphi experts and additionally, one barrier, i.e. lack of acceptance of technology was suggested by the experts which also received ≥75% positive expert consensus. Subsequently, 20 barriers were brought forward from the Delphi Round 2. Accordingly, the applicability of these 20 barriers was separately identified under each of the notable CWM practices in Delphi Round 3 of the study, and the barriers that only received ≥75% positive expert consensus were considered applicable, thus, presented in Table 5 of the study.

As Table 5 explains, low regulatory support and practice, and low knowledge and experience were common for most of the CWM practices. Experts ascertained the reason as the comparative novelty of the two concepts of BC and CE and the governments are also generally thrusting with conventional methods without implementing newly introduced concepts. Lack of acceptance of the technology was also identified by the experts as a common barrier since the incorporation of BC-enabled CE processes into the existing CWM practices will be hindered by the resistance of the stakeholders in adapting novel technologies due to the risk-averse nature of the construction industry. Furthermore, the lack of efficient communication and collaboration is also applicable to most of the CWM practices since the integration of BC-enabled CE principles will require increased collaboration, which is comparatively lesser in the construction industry. As experts suggested, priority should be given to the common barriers since they will have the highest influence on the integration of BC with CE to improve existing patterns of WM in the construction industry.

With the advancement of the construction sector, the corresponding environmental impacts are increasing leading to excessive waste generation (Munaro and Tavares, 2023). Therefore, in reducing the environmental impact, concepts such as BC and CE can be used (França et al., 2020; Norouzi et al., 2021). When considering the practical applicability of BC and CE in the construction sector, literature findings revealed that these concepts are used mostly in developed countries and in other countries, the applications are in the infancy stages (Kouhizadeh et al., 2019). Empirical findings also confirmed that BC and CE are in a development stage related to the construction industry. Furthermore, it was revealed that the CE concept is being more practised in the construction industry than the BC concept. Nevertheless, according to the experts’ opinion, it is possible to integrate BC and CE to improve WM in the construction industry.

WM entails the collection, transportation, recycling and disposal of waste including the supervision of these processes and the maintenance of disposal facilities (Kuhl and Schnitz-Felten, 2020). According to the literature findings, 14 WM practices were identified and during Delphi Round 2, experts confirmed that “landfilling”, “incineration”, “disposal” and “burying” follow a linear economy and these practices were claimed to be disregarded as notable CWM practices that can be improved from the integration of BC and CE.

Moreover, waste transportation, reducing practices and hazardous waste treatment were also disregarded considering their less effectiveness towards a sustainable CWM process. On the other hand, redistribution, purchasing sustainable materials and returning/reselling excess/surplus materials were suggested by the experts during Delphi Round 1 as additional CWM practices that were not identified during the literature survey. According to experts, in practice, redistribution could involve reallocating excess materials from one construction site to another within the organisation, purchasing sustainable materials could involve buying recycled materials such as aggregates or certified green building products, and returning or reselling excess materials could involve collaborating with suppliers to return unused items or selling them to secondary markets.

Improving CWM practices is essential to improve the efficiency of the WM process and methods are being used by several organisations to improve WM by adapting BC technology (França et al., 2020). Literature findings revealed that there are seven main methods available for the integration of BC and CE to improve WM. Meanwhile, “Swachhcoin”, “Recereum” and “Plastic Bank” were identified by the experts as organisations that are trying to improve WM using BC (Gopalakrishnan and Ramaguru, 2019). Empirical findings suggested that these organisations aim to make opportunities to link waste sellers and buyers and convert waste into valuable materials. Furthermore, both literature findings and expert interviews confirmed that “cloud computing” (Velazquez, 2022) and “SaaS” (Salesforce, 2022) can be adapted as efficient support for integration. According to the experts’ opinion in Delphi Round 1, all the methods were accepted, and two new methods were suggested i.e. BC for waste trading and CircularChain. Experts proposed these methods as pragmatic ways to combine BC and CE since CircularChain is practically used to monitor and manage the lifecycle of materials, ensuring that they are efficiently reused, recycled or redistributed within the supply chain, and BC-based waste trading platforms are practically used to create secure digital platforms where construction organisations can list, track and trade surplus materials with verified stakeholders. However, Delphi Round 3 findings revealed that the integration methods are different for each CWM practice due to the variety of characteristics of those practices.

Ezeudu et al. (2021) stated that adaptation of CE and WM assists in achieving more sustainable benefits and at the same time, Şahin (2023) argued that in controlling the sectors of the CE perspective, BC technology also has several enablers in ensuring sustainability. Similarly, characteristics of the BC technology can be identified as more beneficial for the improvement of WM (França et al., 2020). Empirical findings also acknowledged the beneficial nature of adapting BC-enabled CE practices in improving CWM, however, barriers to the integration must be identified to perceive the enablers of the integration (Mahpour, 2018). Sahoo et al. (2021) stated that when adapting BC technology there will be more barriers as well as enablers. In this sense, it was suggested by the literature and empirical findings that to enhance the effectiveness of the integration, proper strategic measures must be followed to overcome the said barriers to integration (Şahin, 2023).

During the literature survey, 25 enablers were identified for the integrations of BC, CE and WM and among these enablers, 17 enablers were identified as applicable by the experts for the integration of BC with CE to improve CWM. Furthermore, empirical findings suggested three additional enablers, i.e. introducing certification methods (green/LEED), removal of third party and digital literacy. During the validation of data, it was instructed not to specify particular certification methods since they are context-specific findings, thus, removing the specific certification methods that were given as examples. Simultaneously, literature findings revealed 27 barriers to the integration of BC, CE and WM and experts found 19 of these barriers as applicable to the integration of BC with CE to improve CWM. Furthermore, a lack of acceptance of technology was introduced as an additional barrier during the Delphi survey.

The findings of the study that were presented in Table 4 and Table 5 include methods, enablers and barriers applicable to each CWM practice which can be improved by the integration of BC with CE and as suggested by the experts, a graphical representation was created to provide the maximum benefits of the outcome to the existing body of knowledge. Accordingly, a mind map framework was created indicating the final research outcome, which is presented in Figure 2 of the study.

Figure 2 illustrates the study’s mind map framework which portrays integration methods, enablers and barriers for the convergence of BC with CE to improve CWM. As the framework depicts, there are many common barriers including lack of efficient communication/collaboration, low regulatory support and practice and low knowledge/experience which will have a considerable impact on most of the identified CWM practices towards the integration of BC and CE. Accordingly, priority should be given to overcoming these common barriers since they will accelerate the integration of BC-enabled CE principles into current CWM practices. Specifically, the mind map framework has been validated by experts in the research area and is believed to fill the knowledge gap on the use of BC and CE to enhance WM in the construction industry. Besides, research suggests that there are proven benefits in the integrations of BC, CE and WM (Ezeudu et al., 2021; França et al., 2020; Şahin, 2023; Sahoo et al., 2021), thus, the convergence of BC with CE to improve CWM will certainly reduce the excessive construction waste generation while catalysing the transition to a more sustainable construction industry.

The aim of this study was to investigate the potential of converging BC with CE to improve CWM. The study revealed that the excessive waste generation of the construction sector can be positively addressed using BC-integrated CE applications and the integration methods were revealed as BC for waste trading, CircularChain, the adaptation of the Swachhcoin approach, Plastic Bank concept, Ethereum’s BC Public Network Architecture platform, cloud computing environment, Saas platform, CE–IoT BC with DanKu protocol and Recereum platform. Moreover, it was revealed that it is highly beneficial to integrate BC with CE towards enhancing CWM and the integration will significantly improve the immutable auditing facility, trackability and traceability and sustainability of the WM patterns in construction. Furthermore, lack of efficient communication/collaboration, low regulatory support and practice and low knowledge/experience commonly affect the effective integration of BC with CE in improving CWM. Ultimately, overcoming these barriers will assist in sustaining proper CWM practices with modern insights which will eventually contribute to the transition to a BC-enabled circular-built environment. It is highly recommended to encourage construction organisations to adapt the mind map framework developed in this study since it simplifies the integration of BC and CE for CWM. More specifically, state organisations and the government should be convinced of the benefits of integrating BC and CE into WM to obtain the regulatory support that is mandatory for policy development for effective integration.

This study fulfils the existing knowledge gap on how BC can be integrated with CE to improve CWM practices and serves the theory with a comprehensive mind map framework that provides integration methods, enablers and barriers for the BC and CE integration for each notable CWM practice. Furthermore, as industry implications, industry practitioners are given insights through this study to adapt the distinct characteristics of BC to accelerate the transition to a circular built environment. However, this study was limited to the construction industry and related methods of integration, enablers and barriers. Besides, BC-enabled CE applications were not discussed in the study which shows a further research direction. In addition, further studies are directed at the solutions and strategies that can be followed to leverage BC-enabled CE principles in improving the efficiency of existing CWM patterns. Furthermore, it is significant to research on the BC-enabled CE applications, which can be used in each stage of a construction project to address how the integration of BC and CE can be used to improve WM in the construction industry.