Beyond green buildings: circular economy strategies and SDG alignment in India's urban housing sector

1 Introduction

The construction sector plays an influential role in shaping the built environments within which communities live, work, play, and recover from crises. As cities continue to urbanise at unprecedented rates, particularly across the Global South, the decisions made within the construction industry have implications for environmental, social, and economic aspects in development. However, despite the scale and environmental footprint of the sector, it has been slow to align its practices with the United Nations (UN) Sustainable Development Goals (SDGs), often defaulting to narrow performance metrics such as energy efficiency and GB ratings rather than embracing the systemic transformation the SDGs demand.

Circular economy (CE) is a concept that has been popularised in recent times, and within the construction and built environment sectors, has been identified as a relevant method for increasing the sustainability outcomes of the sector. As an economic system targeting zero waste and pollution across the full lifecycle of resources, CE offers construction a pathway beyond the linear take-make-dispose model that has long characterised the sector (Nobre and Tavares, 2021). However, a persistent misconception positions CE primarily as a waste management strategy, obscuring the higher-order priorities of reduction, reuse, and repair that are essential to a genuine circularity transition (Gajanayake and Iyer-Raniga, 2025). Although CE has gained popularity and falls within the broader sustainability paradigm, it receives no explicit reference within the SDG framework itself. CE could typically understood to directly address SDG12: Responsible Consumption and Production, and from a built environment angle, address SDG11: Sustainable Cities and Communities and SDG8: Decent Work and Economic Growth. The misconception that CE is predominantly a waste management strategy has limited its relevance to other SDGs, resulting in a conceptual disconnect that practitioners and policymakers must actively work to bridge.

Education for sustainability, institutional reform, and cross-sectoral collaboration have been identified as critical levers for closing this gap. Universities, as thought leaders and catalysts for systemic change, carry a particular responsibility in building the awareness, technical capacity, and mindset shifts required to align construction practice with sustainable development objectives (Serrano-Bedia and Perez-Perez, 2022). This is especially true in the Global South, where socio-economic dimensions of the SDGs, such as poverty, inequality, and access to adequate housing, are inseparable from environmental goals, yet remain underrepresented in how the sector frames its sustainability agenda. This is further exacerbated by the fact that CE objectives focus more on the environmental pillar of sustainability, than on the economic dimension and to a lesser extent, on the social aspects. As CE is an economic model that ultimately aims to achieve sustainable and regenerative outcomes, it is vital that practitioners in the construction sector understand how it can be utilised to achieve broader SDGs.

This study examines how CE practices within the built environment sector may influence the achievement of SDGs in the global south. We draw on practitioner insights from generated through a participatory workshop designed to support the application of CE in the Indian built environment sector. The workshop functioned both as a capacity-building platform and a structured setting for data collection, with focus group discussions (FGDs) embedded as the primary mechanism for eliciting practitioner insights. The overall FGD design enabled participants to collectively identify influential factors in CE adoption, develop CE-oriented strategies, and consider their broader sustainability implications, specifically in relation to SDG alignment.

2 Theory and policy context

The 2030 Agenda for Sustainable Development establishes 17 Sustainable Development Goals and 169 associated targets intended to guide national, sectoral, and project-level decision-making towards a more equitable and environmentally sustainable world (Allen et al., 2016). The SDGs operate as a value-oriented, top-down framework, articulating normative objectives at the global level that cascade downward through national policy and sectoral strategy (Biermann et al., 2017; Kanie and Biermann, 2017). While this structure provides a coherent set of reference points for aligning diverse actors, it can also create implementation gaps when sectors lack the conceptual tools, institutional capacity, or enabling policy environments to translate high-level goals into operational practice.

The construction sector plays a major role in achieving the SDGs as the sector is a driver of urbanisation, infrastructure development, and material consumption, which in turn affect the environmental and economic wellbeing of societies (Ogunmakinde et al., 2022). The sector could be related to virtually every dimension of the SDG framework, from SDG 11: Sustainable Cities and Communities and SDG 9: Industry, Innovation and Infrastructure to SDG 6: Clean Water and Sanitation, SDG 7: Affordable and Clean Energy, and SDG 13: Climate Action. Yet the sector's engagement with the SDGs has tended to be selective and fragmented, gravitating towards goals that align with established performance metrics such as energy efficiency, GB certification, and waste reduction, while neglecting the socio-economic and ecological dimensions of the goals. This selective engagement reflects a broader pattern in which the SDGs are treated as a reporting or legitimacy tool rather than a transformative framework demanding systemic change.

2.1 Defining CE and GB

Before examining CE–SDG linkages, it is necessary to distinguish between CE and GB, two concepts that are frequently conflated in practice but are conceptually distinct. GB refers to a performance-based approach to optimising the environmental efficiency of individual buildings through design, construction, and operational standards. GB systems such as LEED, BREEAM, and GRIHA measure performance across energy use, water consumption, indoor environmental quality, and materials, but primarily within the lifecycle boundary of a single building.

By contrast, CE is an economic system targeting zero waste and pollution across the full resource lifecycle, encompassing a hierarchy of strategies from reducing material demand and reusing components to repairing, remanufacturing, and at the lowest order recycling (Potting et al., 2017). CE extends beyond building-level efficiency to systemic value retention, material loop design, and the transformation of supply chains and industrial systems. Crucially, CE is not a goal in itself but an enabling framework, a means to achieve sustainable development, including the SDGs. The key distinction is that GB optimises performance within the existing system, while CE seeks to redesign the system itself.

This distinction is important because the misconception that CE is primarily a waste management strategy limits its relevance to a narrow range of SDG targets, primarily SDG 12. Recognising CE as a systemic transformation framework opens its potential contribution to health, employment, urban resilience, institutional reform, and ecological restoration, dimensions addressed across the full breadth of the SDG framework.

2.2 Conceptual alignment between CE and SDG

Although CE is not explicitly named within the SDG framework, prior work undertaken through the Sustainable Buildings and Construction (SBC) programme of the One Planet Network (OPN) provides a more sector-specific starting point for examining CE–SDG alignment in the built environment (Iyer-Raniga, 2024a, 2024b). This work positions the SDGs as an exploratory basis for understanding circularity in buildings and construction, rather than as a definitive causal framework. It also indicates that the principles underpinning circularity and sustainability overlap through their concern for social, economic, and environmental outcomes, including resource efficiency, material circulation, reduced reliance on virgin resources, long-term value retention, and regenerative outcomes (Iyer-Raniga, 2024a, 2024b). Building on this prior alignment work, Table 1 presents a starting analytical framework for examining CE–SDG linkages in the Indian urban housing context. The table is not intended to provide an exhaustive or definitive alignment of circularity to the SDGs. Rather, it identifies SDGs and targets that are especially relevant to circular built environment strategies.

Table 1. Starting framework for CE–SDG alignment in the built environment [developed from Iyer-Raniga (2024a, 2024b)].

This initial framing reinforces the need to move beyond treating CE as a narrow waste-management agenda. SDG 12 remains the most direct point of connection because CE promotes sustainable consumption and production through resource efficiency, material footprint reduction, waste prevention, recycling, reuse, and, at the systemic level, the transformation of industrial production and consumption systems (Benachio et al., 2020; Finamore and Oltean-Dumbrava, 2024). In the built environment, CE also directly intersects with SDG 9 and SDG 11 by supporting sustainable infrastructure, innovation, resource-efficient construction systems, housing quality, and sustainable cities (Firoozi and Firoozi, 2022). It further connects with health, employment, water and energy systems, climate resilience, ecosystem protection, and implementation partnerships. Prior SBC/OPN mapping work similarly identifies SDGs 9, 11, 12, and 13 as core to circular built environments, while also highlighting the relevance of SDGs 6, 7, 8, 9, 11, 12, and 17 in Global South contexts (Iyer-Raniga, 2024a, 2024b). This broader framing is particularly important in urban housing contexts, where material circularity, affordability, liveability, local capacity, and climate vulnerability are closely linked.

When properly operationalised, CE can function not as a single-SDG solution but as a process that advances multiple goals simultaneously. Circular approaches to housing delivery can contribute to SDG 11 by improving housing adequacy and affordability, and by enhancing urban resilience, while employment generation within circular supply chains and recycling operations can advance SDG 8: Decent Work and Economic Growth. Health and wellbeing outcomes (SDG 3) are also relevant, particularly where circular and sustainable housing strategies reduce pollutant exposure and improve indoor environmental quality. However, current practice in the construction sector reveals that most interventions tend to cluster around environmental aspects, particularly those related to materials and pollution, while socio-economic goals such as health and decent work remain peripheral to how the industry frames its sustainability contributions (Le et al., 2025). This shows that aligning and positioning CE to cover a broad range of SDGs is vital for the construction sector to play its part in helping achieve the SDGs, which requires systemic awareness and education among practitioners.

Beyond material and technological interventions, the transition towards a CE in the built environment is fundamentally shaped by education and professional capacity strengthening through sustainability-oriented learning (Rao et al., 2025; Quashie et al., 2024; Calle Müller et al., 2024). SDG 4.7 explicitly recognises the role of education for sustainable development (ESD) in equipping individuals with the knowledge and skills needed to advance sustainable practices (UN General Assembly, 2016). In the Global South, structured opportunities for built environment professionals to engage with CE principles remain limited, particularly outside formal education pathways. Within this context, practitioner-oriented training and dialogue-based initiatives play a critical role by supporting shared understanding, reflective practice, and the translation of circular concepts into sector-specific strategies (Reed, 2008; Rieckmann, 2017; Rodríguez Aboytes and Barth, 2020; Senaratne et al., 2023).

Such capacity-building approaches can also be aligned with SDG 13.3, which emphasises improving education, awareness-raising, and institutional capacity related to climate change mitigation and adaptation (Dupuis et al., 2025). In the context of CE transitions in the built environment, this linkage is particularly salient, as circular strategies (such as material recirculation, resource efficiency, low-carbon or circular designs) are intrinsically connected to climate mitigation and adaptive capacity (Gallego-Schmid et al., 2020; Cantzler et al., 2020; Wang et al., 2022). In addition, SDG 17.9 and SDG 17.16, which respectively call for enhanced capacity-building support in developing countries and the promotion of multi-stakeholder partnerships for sustainable development (Cruz, 2023). Jointly, these SDG targets signal that CE transitions are not solely technical or material shifts, but institutional and collaborative processes requiring strengthened professional competencies and cross-sector knowledge exchange (Ritter et al., 2024; Köhler et al., 2022).

2.3 The Global South and its importance to CE–SDG alignment

The relationship between CE, SDGs, and the construction sector is particularly important in Global South contexts. Countries such as India face intersecting pressures of rapid urbanisation, acute housing deficits, material resource constraints, informal construction practices, fragmented supply chains, limited institutional capacity, and profound socio-economic inequality (Ogunmakinde et al., 2022). These conditions simultaneously intensify the need for CE-aligned construction practices and in turn further complicate their adoption.

CE strategies are typically developed within high-income economy contexts, and therefore are dependent on sophisticated waste sorting infrastructure, formal material markets, high regulatory capacity, and therefore cannot be simply transferred to Global South settings (Ghisellini et al., 2016), which is characterised by informality and varied governance and regulatory structures. This necessitates context-sensitive research that examines how CE principles can be adapted to the specific conditions of the Global South (Korhonen et al., 2018).

Furthermore, in Global South contexts, the social and economic dimensions of the SDGs carry particular weight, where SDGs related to poverty, inequality, health, and decent work are more important, in contrast to high-income countries (Gupta and Vegelin, 2016). This demands that CE application in the construction sector and relevant research move beyond a predominantly environmental framing to engage more with socio-economic co-benefits and trade-offs, including affordability, employment, informal sector integration, and equitable access to sustainable housing.

Although the SDGs provide a widely recognised framework for aligning sectoral action with sustainable development, their universal and top-down structure can also limit recognition of context-specific knowledge systems. As a result, SDG-based alignment can risk privileging globally standardised sustainability categories while underrepresenting local and place-based forms of circularity (Mignolo, 2020). From a built environment perspective, practices in the Global South exhibits indigenous and culturally embedded understandings of land, materials, stewardship, vernacular construction, and community-based resource governance. This limitation is important when interpreting CE–SDG alignment, as target-level alignment may not fully capture the cultural and relational dimensions of sustainability transitions.

This paper explores how education for CE among practitioners can be used to amplify the construction sector’s role in helping achieve SDGs. The following sections present the context of the training sessions and how they were used to understand practitioners' awareness on alignment between CE and SDG aims.

3 Training workshop context and focus group activity design

3.1 Workshop context and stakeholder participation

The training programme was developed as part of an international initiative, Transforming the Built Environment through Sustainable Materials, in selected Global South contexts (Jayawardana et al., 2026). The programme encompasses the design and delivery of training materials and workshops aimed at strengthening CE capacity among built environment practitioners in these countries. The pilot workshop was implemented as a two-day, in-person programme in India, facilitated by two academic researchers from the lead university, with support from the coordinating organisation. Participants were purposively selected to ensure representation across key stakeholder groups in the Indian built environment sector.

A total of 20 practitioners representing 15 organisations participated in the workshop. Figure 1 presents the distribution of the stakeholder groups and their relevance to the built environment ecosystem, illustrating the multi-actor nature of the participatory setting. Stakeholders represented architecture and design consultancies, building material producers and suppliers, policy and technical advisory bodies, real estate developers, research and development organisations, incubators or impact investors, and industry associations. These groups collectively reflect the range of actors influencing decision-making, material flows, design practices, and regulatory frameworks within the Indian built environment sector. As a practitioner-oriented capacity-building initiative, the training programme alignedwith the broader intent of SDG 4.7 on ESD by enabling dialogue, transformative learning, and applied understanding of CE principles in the built environment. It also aligned with the sustainable consumption and production agenda reflected in SDG 12.1 and SDG 8.4, as it sat within the One Planet Network/10-Year Framework of Programmes and its emphasis on resource efficiency, circular material use, and decoupling environmental impacts from built environment development. Additionally, it advanced SDG 13.3 by strengthening awareness and professional capacity related to climate mitigation and adaptation, and contributed to SDG 17.9 and 17.16 by functioning as a collaborative, multi-stakeholder platform that supported institutional capacity-building and partnership-based knowledge exchange in sustainable development.

3.2 Focus group activity design and progression

FGDs were embedded within a sequence of three facilitated group activities, each designed to build progressively on the previous one. Although the workshop included additional thematic sessions for knowledge sharing, this study focuses specifically on the group activities, as they constituted the primary source of empirical data. Each activity functioned as a structured FGD, guided by prompts and case materials, but was deliberately non-prescriptive regarding expected outcomes. A combination of expert input and contextual considerations informed the overall design of these activities. Insights from prior international engagements with built environment practitioners and academics (through the GlobalABC Assembly and Dresden Nexus Conference, April 2025) were complemented by targeted national consultations with the actors in the Indian built environment sector (GlobalABC and UNEP, 2025).

To support contextualisation and applied discussion, an Indian state urban housing ecosystem (Odisha) was selected as a reference case for the FGDs. Odisha was used as a practical contextual anchor rather than as a representative case for all Indian states. Its selection was informed by consultation inputs prior to the workshop and an Odisha-focused roadmap guidance provided by the lead organisation’s country team, which helped anchor the activities in a real-world policy- and practice-relevant housing context. Odisha represents a setting characterised by high housing demand, material-intensive construction practices, and emerging opportunities for CE innovation, including the use of bio-based materials, industrial by-products, and recycled construction and demolition waste (CDW). The reference case, therefore, enabled participants to examine CE strategies in relation to context-specific urban housing pressures, while recognising that findings may differ in other Indian states due to variations in housing markets, governance arrangements, material supply chains, construction practices, and waste-management infrastructure. Situating the FGDs within this context enabled participants to engage with real-world challenges, while generating exploratory and transferable insights with relevance beyond the immediate case. The participatory structure consisted of three sequential group activities, each approximately 1.5 h in duration, designed to build progressively from exploration to synthesis. The workshop was intentionally structured to promote diverse dialogue, with participants from the same organisation assigned to different discussion groups (a total of four groups: A–D) to encourage interaction across professional backgrounds and minimise institutional dominance within individual FGDs. This grouping strategy facilitated the generation of diverse perspectives and enabled collective sensemaking around CE strategies and SDG challenges in urban housing contexts.

The first activity (FGD1) focused on system exploration, during which participants collectively examined the urban housing context to identify key stakeholders, drivers, and constraints influencing the adoption of CE principles. The second activity (FGD2) shifted towards strategy formulation, inviting participants to discuss feasible design and material strategies to operationalise CE approaches within urban housing, with a particular focus on low-income groups (LIGs). The third activity (FGD3) centred on intervention synthesis, requiring participants to integrate insights from the earlier discussions into consolidated CE interventions. At this stage, SDG considerations were explicitly foregrounded, and participants were asked to reflect on how proposed interventions relate to broader SDGs. SDG engagement during the workshop was exploratory and time-bounded, and no predefined set of goals was imposed on participants. During the third activity, facilitators provided each group with a specific SDG to prompt them to identify how the selected intervention will impact the selected SDG. Each group was provided with an SDG, which had little commonality with the intervention they had selected (see Table 2). This approach was intended to encourage participants to consider less familiar or less obvious sustainability connections beyond the SDGs most commonly associated with CE and the built environment. Participants were informed that CE and built environment interventions typically address SDGs 11 and 12, and the objective was to determine how the proposed interventions could be modified to address other SDGs as well. This prompting supported exploratory reflection, but it may also have influenced the salience of particular CE–SDG linkages during the group discussions. As a result, the SDG associations that emerged during the discussions reflect participant reasoning within the constraints of the workshop setting, rather than a comprehensive or systematic assessment of SDG alignment. Accordingly, participant-articulated SDG associations were treated as workshop-generated reflections, while the subsequent target-level alignment analysis was conducted separately using intervention-specific mechanisms and classified as direct, enabling, or contextual.

Table 2. Specific SDG targets provided to each group.

4 Data analysis

4.1 Focus group discussion outcomes analysis

This study adopted a qualitative research design, using FGDs conducted within the participatory workshop setting. The FGDs generated multiple forms of qualitative material, including visual artefacts (e.g., annotated posters and strategy maps) and collective reflections during feedback sessions. Although SDG and sustainability considerations were most explicitly discussed during the FGD3, the empirical materials were generated sequentially across all three FGDs. Accordingly, the dataset was treated as a single, sequential body of qualitative evidence capturing practitioner reasoning and sustainability-oriented sensemaking. To examine how practitioner-identified CE interventions relate to the SDGs, the study employed a two-layered qualitative analytical approach as illustrated in Figure 2. The first layer captured participant-explicit SDG associations, reflecting the SDGs that practitioners articulated during the time-bounded FGD3. These associations indicate the sustainability goals that were more salient relative to collective sensemaking and readily expressed in the participatory setting. The second layer involved a qualitative content analysis (QCA) of the same intervention data to identify SDG alignment. Rather than inferring participant intent, this step examined how intervention components align with the SDGs through their underlying mechanisms.

Figure 2 presents the overall analytical workflow, while Table 3 summarises the coding framework used to move from workshop-generated intervention data to the prioritised CE–SDG alignment analysis. The coding process combined deductive structuring, based on the FGD prompts and intervention template, with inductive interpretation of intervention-specific mechanisms and implementation conditions. This coding framework supported traceability between the original FGD outputs, intervention components, SDG target assignments, and prioritised alignment categories.

Table 3. Coding framework for CE–SDG alignment analysis.

QCA was conducted using a hybrid inductive-deductive strategy (Fereday and Muir-Cochrane, 2006). In qualitative research, QCA is a flexible but systematic text-analysis method that uses coding rules and category systems to reduce, describe, and interpret textual data (Mayring, 2014). Deductive analysis uses established theories or frameworks to inform coding and categorisation, while inductive analysis is employed when prior knowledge is limited, allowing themes and categories to emerge from the data (Elo and Kyngäs, 2008). Many research studies employ a hybrid approach, starting with deductive coding and subsequently allowing inductive categories to emerge as the analysis progresses (Graneheim et al., 2017; Kleinheksel et al., 2020). In this study, deductive coding was guided by the structured prompts embedded within the group activities, while inductive coding allowed themes to emerge from the empirical material (i.e., implementation drivers; see Figure 2). Analysis progressed iteratively through familiarisation, coding, categorisation, and synthesis. To support the SDG alignment analysis, intervention data were examined through four analytical elements: (i) sustainability benefits (SB), (ii) implementation drivers (ID), (iii) material strategies (MS), and (iv) design strategies (DS). These elements enabled systematic interpretation of how CE interventions operate across technical, organisational, and strategic dimensions relevant to sustainability transitions in the built environment sector.

SDG alignment was examined at the level of the 17 SDGs (goal level) and their associated targets rather than at the level of SDG indicators. This reflects both the qualitative, exploratory nature of the study and the analytical scale of the data, which focused on intervention logic, strategy design, implementation pathways, and practitioner reasoning. These domains operate primarily at policy, design, and system levels, aligning more naturally with SDG goals and targets that articulate intent, scope, and transformation mechanisms, rather than with indicators intended for monitoring and quantitative evaluation. Moreover, while SDG targets remain broad and multi-dimensional, they provide a more appropriate interpretive bridge between high-level sustainability goals and the operational logic of CE interventions, particularly when examining complex socio-technical systems such as the built environment.

Importantly, SDG target alignment was conducted through an intervention-specific analytical lens rather than assuming that all circular strategies uniformly contribute to the same SDG targets. Each intervention was treated as a distinct mechanism of change, and alignment was derived from its specific material, design, implementation, and sustainability characteristics. To prioritise SDG associations, each target-level linkage was further classified as direct, enabling, or contextual. This simplified classification was informed by SDG interaction frameworks that distinguish stronger reinforcing linkages, enabling relationships, and more conditional or context-dependent associations (Nilsson et al., 2016; Griggs et al., 2017; Nilsson et al., 2018). In this study, direct alignment refers to intervention components with a clear and immediate mechanism connected to the SDG target; enabling alignment refers to linkages mediated through policy, technical, financial, behavioural, institutional, or collaborative conditions; and contextual alignment refers to broader co-benefits that depend more strongly on implementation context.

This intervention-lens-based approach ensured that targets were mapped based on demonstrated causal pathways within each intervention (see Supplementary material for each alignment, including the causal connections and prioritised alignments). This analytical approach builds on prior SDG-circular built environment research, which used large-scale international surveys and regional expert validation across multiple Global South contexts (e.g., over 180 survey responses spanning Asia, Africa, and Latin America) to identify priority SDGs, targets, and indicators (Iyer-Raniga, 2024a, 2024b; Huovila and Iyer-Raniga, 2022). The alignment process in this study was conducted collaboratively by three researchers with prior experience in SDG-based research and established expertise in sustainable development and the sustainable built environment. Formal inter-coder reliability statistics were not calculated, given the exploratory and interpretive nature of the analysis and the structured format of the workshop-derived intervention data. Target assignments were iteratively discussed and refined to ensure conceptual coherence and consistency with both SDG intent and intervention-specific mechanisms. The researchers reviewed the consistency between intervention components, causal linkages, and the direct, enabling, or contextual alignment categories. Where ambiguities arose, particularly in distinguishing CE-specific mechanisms from GB-oriented strategies or in assigning alignment strength, the intervention data and SDG target descriptions were revisited, and classifications were resolved through discussion and consensus. Full sub-factor-level classifications were retained in Supplementary material to support analytical traceability.

4.2 Follow-up interviews

Follow-up interviews were conducted approximately three months after the workshop to provide complementary interpretive evidence on post-workshop reflection and application. Five workshop participants and one observer from the organising team were interviewed. The participant group included representation from NGO/civil society, academia/research, and three built environment practitioners, while the observer represented a multilateral organisation.

Interview recordings were transcribed verbatim, anonymised, and imported into NVivo. A deductive QCA approach was used, with coding structured around the interview guide and used as predefined thematic nodes. These nodes covered salient workshop takeaways, learning process and experience, post-workshop influence and application, interaction and peer learning, barriers and constraints to application, and CE-sustainability conceptual integration. The interview findings were not used to generate or directly validate SDG target assignments because the interview guide did not include SDG-specific questions. Instead, they were used to contextualise the prioritised SDG alignment results, particularly in relation to higher-order circular thinking, CE–GB boundary interpretation, implementation barriers, and conditionality of SDG contribution pathways.

5 Results

This section presents four practitioner-derived interventions (Groups A–D) to illustrate pathways for advancing CE principles in urban housing systems in India. These interventions reflect complementary design, material, governance, and system-level strategies, with SDG linkages examined through participant articulation, prioritised analytical interpretation, and follow-up interview insights on higher-order CE understanding, CE–GB boundaries, and implementation barriers. It should be noted that participant’s SDG associations reported below emerged within a prompted workshop setting in which facilitators assigned specific SDGs to each group. These associations therefore reflect practitioner reasoning within that structured context, which were influenced by researcher prompts.

5.1 Practitioner-derived CE interventions

Group A identified an intervention around the adoption of smart, circular design principles and low-carbon and alternative material choices in housing projects for LIGs in India, intending to reduce life cycle resource consumption while making housing more affordable. Participants initially associated this intervention with SDG 12, while the facilitator-prompted SDG led the group to incorporate integrated water harvesting, treatment, and reuse systems. These participant-articulated associations suggest that practitioners primarily framed this intervention through resource efficiency, reduced material demand, and localised water security. Intervention B centred on integrating a GB certification framework as a channel for diffusing CE practices in urban housing in India. Participants primarily aligned Intervention B with SDG 11 and SDG 12, with additional emphasis on SDG 14 and SDG 17. These associations indicate that participants viewed certification as a possible governance and coordination mechanism for improving environmental performance, material and waste management, and multi-stakeholder collaboration.

Intervention C focused on improving thermal comfort and mitigating urban heat island (UHI) effects through passive design, material-based cooling strategies, urban greening, and energy-efficient systems. Participants primarily aligned this intervention with SDG 11 and SDG 7. However, the intervention was more strongly framed through GB performance logic than CE logic, as most proposed strategies addressed operational efficiency, liveability, and heat resilience rather than material loops or whole-life value retention. This makes Intervention C important for interpreting the conceptual boundary between CE and GB in practitioner reasoning.

Intervention D proposed piloting a CDW recycling facility to recover and reintegrate construction materials into urban housing projects. Participants framed the facility as both a technical and institutional solution, supported by policy mandates, partnerships, and the integration of renewable energy. Participants primarily associated this intervention with SDG 7 and SDG 12. These associations reflected concerns related to energy efficiency, material recovery, and reducing landfill dependence.

5.2 Prioritised SDG alignment by intervention

The following sub-sections present the prioritised SDG alignment for the four interventions, distinguishing core pathways from broader conditional linkages while retaining the full causal alignment in Supplementary material.

5.2.1 Intervention A: adoption of smart design and circular materials

As shown in Table 4 intervention A shows the clearest direct alignment with targets related to resource efficiency, water circularity, material optimisation, and adaptable design. The adoption of smart design principles and circular materials directly associated with Target 12.2 by reducing reliance on virgin raw materials and lowering life cycle resource use intensity. Strategies such as blended cement, lightweight walling systems, and optimisation of steel and water use minimise material throughput, while design for adaptability is linked to Target 12.5 by preventing demolition waste and extending building lifespans (Shanks et al., 2019; Habert et al., 2020; Pokorný et al., 2021; Munaro and Tavares, 2025). These material and structural efficiencies also support Target 9.4 by promoting cleaner production pathways and encouraging the diffusion of low-carbon construction technologies within the housing sector.

Table 4. SDG alignment of intervention A across key components.

Climate mitigation appears as a secondary/enabling alignment through Target 13.2. Low-carbon material selection, passive design strategies, and engineering optimisation reduce embodied and operational emissions at the point of decision-making rather than through later-stage revisions (Fang et al., 2023; Elaouzy and El Fadar, 2022). Passive design principles further connect with Target 7.3 by lowering operational energy demand through strategies such as climate-responsive building orientation, envelope performance, and daylight optimisation (Konis et al., 2016; Pajek and Košir, 2021). Water-focused strategies such as rainwater harvesting, treatment, and decentralised wastewater reuse systems show direct alignment with Targets 6.3 and 6.4 by improving water quality and increasing water-use efficiency at building and precinct scales (Zang et al., 2021; Das et al., 2025). Reduced freshwater extraction and controlled discharge pathways may also indirectly support Target 14.1, although this linkage remains more contextual because it depends on the effectiveness of wastewater treatment and runoff control.

The intervention also operated through institutional and enabling mechanisms. Regulatory guidelines and incentives for circular design are associated with Target 12.1 by operationalising sustainable consumption and production principles within housing policy frameworks, while incentives for developers and end-users may support Target 12.6 by encouraging uptake of sustainable practices. Digital platforms and design-support tools provide enabling links to Targets 9.c and 17.8 through enhanced access to enabling technologies. On-site training, workshops, and demonstration projects support practitioner competence and sustainability literacy under Targets 4.7 and 13.3, indicating the socio-institutional learning function of the intervention (Kioupi and Voulvoulis, 2019). Broader links to health, quality of life, and awareness are retained as secondary or contextual alignments because they depend on material toxicity, user exposure, communication mechanisms, and implementation quality.

5.2.2 Intervention B: integration of a green building certification framework

As shown in Table 5, Intervention B combines direct CE-relevant linkages with several GB-oriented performance linkages. Integrating a GB certification framework is most directly associated with Target 7.3, where certification criteria reduce operational energy demand, and with Target 13.2, where climate mitigation requirements are embedded within formal design and operational criteria. Certification systems translate climate-responsive principles into measurable standards, as a result, institutionalising decarbonization within routine housing delivery (Kochhar et al., 2022). Operational cost reductions achieved through water and energy efficiency may support Targets 6.4 and 8.4 by highlighting the economic savings arising from improved resource productivity. Comfort, indoor environmental quality, and reduced pollutant exposure are contextual or enabling links to Target 3.9, while strengthened housing quality and safety may support Target 11.1. At the urban scale, enhanced building performance can contributes to Target 11.6 by reducing pollution burdens and ensuring proper waste management associated with inefficient housing systems.

Table 5. SDG alignment of intervention B across key components.

*Target also appears at a lower alignment level for other sub-factors within the same component.

In terms of governance and coordination mechanisms, technical standards, and performance guidelines show direct alignment with Target 12.1, transforming voluntary sustainable efforts into codified requirements. Policy support for certification enables alignment with Targets 11.b and 13.2 by integrating resource efficiency and climate resilience within formal urban sustainability frameworks. Financial instruments such as carbon-linked credits and rating mechanisms may support Targets 8.4 and 13.2 by rewarding mitigation-oriented design and operational decisions. However, structural incentives in carbon offset markets favour volume over environmental integrity, requiring reforms, insurance mechanisms, and stronger oversight to avoid greenwashing and ensure real mitigation (Cabiyo and Field, 2025; Delacote et al., 2024; Sasaki, 2025). Certification frameworks also provide an enabling platform for Targets 17.16 and 17.17through cross-sector collaboration.

Preference for local, low-carbon, and recyclable materials is directly relevant to Target 12.2 when it reduces virgin resource demand and supports circular material management. However, scaling infrastructure and technology for circular flows, procurement and market systems, and enabling policy mix are needed to make these preferences the default (Chiappinelli et al., 2021; Zhang et al., 2025; Govindan and Hasanagic, 2018). Design for deconstruction shows clearer CE alignment with Targets 12.2 and 12.5 by facilitating material recovery and reducing demolition waste. Passive design and green operational optimisation remain stronger GB linkages to Targets 7.3 and 13.2 unless they are explicitly connected to whole-life resource efficiency and circular value retention.

5.2.3 Intervention C: design for thermal comfort (building and urban scale)

As shown inTable 6, Intervention C has its strongest primary/direct alignment with targets related to energy efficiency, urban heat reduction, public-space greening, and climate adaptation, particularly SDGs 7.3, 11.6, 11.7, 13.1, and 13.2. Reduced heat stress and pollutant exposure may support Target 3.9 by lowering risks associated with hazardous air conditions and extreme temperatures. Enhanced indoor thermal stability has a contextual link to Target 8.8 by contributing to safer and more secure working and living environments, particularly in mixed-use or home-based economic settings common in low-income urban contexts (Handayani et al., 2024; Liaw et al., 2023). Further, reduced ambient heat and improved air quality are associated with Target 11.6, while vegetation-based cooling and shading strategies may support Target 15.1, where urban greening is designed and maintained to enhance ecosystem resilience. Reductions in cooling demand show direct alignment with Target 7.3 by accelerating improvements in energy efficiency, as passive design, daylight optimisation, cool roofs, and high-performance envelopes lower reliance on mechanical cooling (Hu et al., 2023; Sarihi et al., 2021; Chen et al., 2023). These measures also support Target 13.2 by integrating climate-responsive design into building form and material selection. Moreover, mitigation of UHI is directly linked to Target 13.1 by strengthening adaptive capacity to climate-related hazards, particularly extreme heat events that disproportionately affect dense low-income housing areas (Heaviside et al., 2017; Leal Filho et al., 2018). Thermal comfort interventions that prioritise vulnerable and low-income populations may support Target 10.2 by improving equitable access to safer indoor environments, while improved thermal performance can contribute Target 11.1, where it enhances habitability and housing adequacy.

Table 6. SDG alignment of intervention C across key components.

*Target also appears at a lower alignment level for other sub-factors within the same component.

Urban greening policies show direct alignment with Targets 11.7 and 13.1 where they expand access to inclusive green spaces and increasing resilience to heat-related hazards. For instance, large comparative modelling has shown that urban greening strategies such as urban vegetation can cool European cities by 1.07 °C on average, and up to 2.9 °C; however, at least 16% tree cover is needed for a 1 °C reduction in urban temperatures (Marando et al., 2022). Cool roofs and reflective materials are directly linked to Target 7.3 and may support 13.2 by lowering operational energy intensity. Bio-based or recyclable insulation materials provide the clearest CE-related linkage within this intervention through Target 12.2, but only where material choices reduce resource intensity, improve durability, or enable end-of-life recovery. Building codes and performance standards enable alignment with Targets 11.b and 13.2 by formalising climate-responsive design requirements within regulatory frameworks. Acceptance and adoption of GB measures may support Targets 4.7, 12.6, and 12.8 by strengthening sustainability literacy and awareness of thermal design benefits.

5.2.4 Intervention D: pilot CDW recycling facility

As shown in Table 7, intervention D has a direct CE alignment through its core mechanism of CDW recovery, recycled aggregate production, landfill diversion, and reduced virgin material extraction. The recovery and processing of CDW into secondary aggregates is directly associated with Target 12.2 by reducing dependence on virgin sand, gravel, and mineral extraction, and Target 12.5 by substantially reducing waste generation through recycling and reuse. By diverting materials from landfill and reintroducing them into new housing projects, the intervention supports circular material flows across the construction life cycle. Jain et al. (2020) showed that integrated wet recycling is an environmentally sound alternative to landfilling for CDW in urban India, recovering over 95% of the incoming flow. Reduced extraction pressure may also support Target 15.1 by limiting land disturbance and ecosystem degradation associated with quarrying activities (Alsheyab, 2022).

Table 7. SDG alignment of intervention D across key components.

Resource recovery pathways further show direct alignment with Target 9.4 by upgrading infrastructure and promoting more resource-efficient industrial systems within the construction sector. The energy savings associated with secondary material production provide an enabling link to Target 7.3, as recycled aggregates typically require lower processing energy than primary materials (Gruhler and Schiller, 2023; Hossain et al., 2016). Reductions in landfill-related emissions and embodied carbon from virgin production may support Target 13.2, although the strength of this linkage depends on transport distance, facility energy source, processing efficiency, and actual displacement of virgin materials. Lower landfill dependency and improved waste containment may also support Target 11.6 by reducing urban pollution burdens and environmental degradation (Purchase et al., 2021). Cost savings derived from reduced landfill disposal, material substitution, and energy conservation show an enabling alignment with Target 8.4 by demonstrating that efficiency gains can decouple economic activity from environmental degradation. Employment generation within recycling form a contextual linkage to Targets 8.5 and 9.2 because job creation depends on facility scale, labour formalisation, safety standards, and stable markets for recycled products. Improved sanitation and controlled handling of CDW may support Targets 3.9 and 6.3 where exposure to waste-related pollutants and leachate risks are reduced.

Looking into the institutional dimension, recycled-content mandates in new construction projects show direct alignment with Targets 12.2, 12.5, and 12.7 by embedding circular material requirements within procurement and planning frameworks (Shooshtarian et al., 2025; Ghaffar et al., 2020). Engagement with redevelopment projects may support Target 11.3 by enabling coordinated and sustainable urbanisation processes that integrate material recovery at source. Partnerships with renewable energy providers form enabling links to Targets 7.2 and 13.2 by reducing operational emissions of recycling facilities. Collaboration with research and development institutions supports Targets 9.4 and 9.5 by enhancing technological capabilities and recovery efficiency, while multi-sector partnerships may support Target 17.17through coordinated public–-private innovation.

5.3 Cross-intervention SDG patterns

Table 8 synthesises the cross-intervention patterns emerging from the prioritised alignment analysis. The clearest CE-related alignments are concentrated around resource efficiency, circular material flows, sustainable infrastructure, and waste reduction, particularly targets 12.2, 12.5, 12.7, 9.4, and 9.5. These targets are most strongly represented in Interventions A and D, where the underlying mechanisms relate directly to material optimisation, adaptability, water reuse, CDW recovery, recycled-content procurement, and reduced virgin resource demand. Energy efficiency and climate-response targets, especially 7.3, 13.1, and 13.2, are also prominent, but their meaning differs across interventions. In Interventions B and C, these linkages primarily reflect GB, certification, thermal comfort, and decarbonization pathways rather than CE-specific value-retention mechanisms. By contrast, in Intervention A, they are connected to passive design and resource-efficient planning, while in Intervention D, they operate mainly as enabling conditions through renewable-powered recycling operations.

Table 8. Cross-intervention patterns in prioritised SDG alignment.

Broader social, health, employment, ecosystem, and partnership-related targets appear across the intervention set, but mostly as secondary or contextual alignments. Their contribution depends on implementation conditions such as affordability, material performance, labour safeguards, pollution control, infrastructure readiness, user access, and governance support. This pattern suggests that CE–SDG alignment in Indian urban housing should be interpreted as a differentiated set of direct, enabling, and conditional pathways rather than a uniform set of positive associations.

5.4 Follow-up interview insights

5.4.1 Movement towards higher-order circular thinking

The interviews indicated that some participants moved beyond recycling-oriented interpretations towards higher-order circular thinking. Participants referred to the importance of “rethink” and “reduce” strategies, long-term solutions, dismantling, reuse, and life-cycle evaluation. For example, one participant explained that, in developing prefabricated panels from bio-based materials, the workshop encouraged consideration of how panels could be dismantled and reused rather than demolished and recycled. This supports the interpretation that CE learning was strongest where participants connected circularity with design-stage decisions, adaptability, material recovery, and whole-life value retention.

5.4.2 CE–GB boundary interpretation

The interviews reinforced the CE–GB boundary issue identified in the intervention analysis. Some participants distinguished CE from GB by framing circularity as a deeper requirement for reuse and resource retention, with one participant suggesting that green buildings need to become more circular to achieve stronger sustainability outcomes. In contrast, another participant positioned circularity as one of the pillars of a GB. These contrasting views indicate that CE–GB overlap is not only an analytical classification issue (identified through QCA) but also a practitioner sensemaking issue. This finding is particularly relevant to Interventions B and C, where certification, operational performance, passive design, and thermal comfort generated strong sustainability linkages but weaker or more conditional CE-specific pathways.

5.4.3 Implementation barriers and conditional CE–SDG pathways

Participants identified several barriers that may shape the practical realisation of CE–SDG pathways (Table 9). These included cost disadvantages of emerging materials, low stakeholder awareness, policy-infrastructure misalignment, limited CDW processing capacity, weak academia-industry linkages, misconceptions about material performance, and market preference for conventional low-cost solutions. These barriers suggest that the SDG linkages identified in Tables 3–6 should be interpreted as potential contribution pathways rather than automatic outcomes. Implementation depends on enabling conditions such as material standards, procurement demand, infrastructure readiness, capacity building, environmental safeguards, and stakeholder coordination.

Table 9. Practitioner identified barriers for CE integration in built environment projects.

*N_P refers to the number of participants who referenced the factor at least once, not the total frequency of mentions.

These follow-up insights together contextualise the prioritised SDG alignment analysis by showing that CE implementation is shaped not only by technical intervention design, but also by practitioner interpretation, market acceptance, institutional readiness, and the unresolved boundary between CE and GB.

6 Discussion

The results of the analysis show that all groups identified that the most appropriate interventions from a circularity standpoint centre around reducing virgin resource consumption and keeping materials in productive use, whether through circular design (A), certification standards (B), passive cooling materials (C), or CDW recycling (D). This reinforces the fact that CE is typically seen from a sustainable production and consumption lens (Geissdoerfer et al., 2017; Pomponi and Moncaster, 2017). However, most CE interventions were framed as a systemic goal rather than an isolated technical fix, illustrating the need for cross-sectoral collaboration. A common theme among the participants was the inclusion of clean and renewable energy aspects in the interventions. The identified interventions show that practitioners believe that climate action is most effective when integrated early in design through material selection, building orientation, and planning decisions, rather than retrofitted at later stages in the life cycles. Such early-stage interventions have been found to deliver the greatest long-term emissions reductions (Röck et al., 2020), while, from a climate perspective, embodied carbon locked in at the design and material selection stages is a critical and under-addressed issue in the construction sector (Elaouzy and El Fadar, 2022).

The alignment of interventions across the SDG targets shows that each intervention typically touches 8–12 SDG targets simultaneously. This suggests that housing-focused CE interventions are inherently cross-sectoral, linking health, water, energy, employment, and ecosystems. As the case analysed by the practitioners was a social housing project, most interventions have wider benefits on the socio-equity aspects especially to low-income groups through improved thermal comfort, reduced pollutant exposure, safer housing, and job creation, illustrating that CE could be framed not purely as environmental but through a social justice agenda. However, such synergies are not always natural, as it has been found that sustainability and greening interventions can reproduce inequality (Anguelovski et al., 2018), raising important equity questions for CE-housing transitions. The lack of community voices in policy level decision making as well as research, which influences such decisions is a major barrier for advancing social justice issues as raised by the participants (Kunjan et al., 2026). Within research this signifies elite stakeholder bias, where insights from experts are made prominent, while community and beneficiary voices are marginalised and needs to be addressed in future research. It should also be noted that the interconnections identified were more through the reflective alignment exercise, rather than through direct practitioner insights. Therefore, it is vital to analyse the deeper connections between these SDGs as they typically illustrate not only synergies but trade-offs as well (Kroll et al., 2019; Nilsson et al., 2016).

The results also revealed a significant overlap between CE and GB among practitioners, where there is a tendency to conflate GB performance improvements with CE, when in fact CE requires systemic value retention and material loops beyond efficiency gains alone. This conceptual misalignment is reflected in the limited emphasis on interventions targeting higher-order CE practices like refuse, repair and reduce (Potting et al., 2017). This is also reflected in the limited attention given to more strategic CE pathways, including circular procurement, business models, supply chain coordination, governance arrangements, and cross-project material value retention. However, this should be interpreted as a contextually grounded pattern within the workshop-generated interventions rather than as evidence that such strategic CE activities are absent from the construction sector. Given India’s position as a rapidly urbanising emerging economy, the findings may reflect important practitioner tendencies in comparable contexts. However, they may not represent a comprehensive account of strategic CE thinking across the Indian construction sector. Although this conceptual knowledge gap was identified at the early stages of the project and care was taken by facilitators to explain the distinction between CE and GB, the distinction was only partially reflected in the identified interventions. This suggests that the operationalisation of CE in practice may remain shaped by dominant GB-oriented sustainability paradigms, particularly where short, time-bounded learning activities are insufficient to fully transform established practitioner mental models. This indicates the need for sustained learning and capacity-strengthening processes that move beyond one-off or time-bounded capacity-building activities, allowing practitioners to revisit, reflect on, and translate CE concepts into project and organisational decision-making over time.

It is important to note that the SDG linkages identified in this study represent potential pathways rather than actual outcomes, and that CE interventions may also generate trade-offs between SDGs. For example, CDW recycling operations may generate localised pollution and noise, creating tensions between SDG 12 and SDG 3 (health) and SDG 11 (sustainable cities) for proximate communities. GB certification frameworks may improve environmental performance while simultaneously creating affordability pressures for LIG projects, if compliance costs are not offset by incentives, potentially conflicting with SDG 11.1. Economic benefits from circular supply chains (SDG 8) may not be equitably distributed, reproducing inequalities that conflict with SDG 10. These tensions are inherent features of SDG interaction that require explicit navigation through policy design (Kroll et al., 2019; Nilsson et al., 2016).

Practitioner insights also reveal that collaboration between government, industry, research institutions, and communities is positioned as an essential element to circular transition. Collaboration is identified as an essential ingredient in practically all CE and SDG literature (Bocken et al., 2016), sometimes being framed as co-governance or network governance (Iyer-Raniga and Cramer, 2025). The insights also show the need for enabling regulatory frameworks such as certification systems, building codes and procurement guidelines, and the institutional buy-in at the policy level. Again, such findings are not new within the CE literature, where it has long been argued that institutional frameworks and regulatory conditions shape the adoption of circular practices (Golev et al., 2015), while policy coherence is an important element (Chiappinelli et al., 2021). The consistent lack of collaboration and policy and regulatory coherence may mean that transitioning to CE and achieving SDGs is not (at least not yet) considered an overarching policy goal across the construction sector.

7 Conclusions, limitations, and future research

The current study investigated how CE interventions identified by built environment practitioners in India align with the SDGs, using focus group data generated through a practitioner-oriented training workshop on urban housing. The findings show that practitioners mainly framed CE around resource efficiency, low-carbon materials, GB performance, clean energy, and construction and demolition waste recycling, reflecting a strong environmental orientation. Target-level analytical alignment revealed broader SDG linkages than those explicitly articulated by participants, connecting CE interventions with health, employment, housing quality, urban resilience, institutional capacity, and partnerships. However, the findings also highlight a persistent overlap between CE and GB thinking, with limited emphasis on higher-order circular strategies such as reuse, repair, adaptability, design for deconstruction, and systemic value retention. This reinforces the need to move beyond performance-efficiency approaches towards more holistic circularity transitions in the built environment.

The study acknowledges the following limitations. First, the study is based on a single workshop conducted in India, with a relatively small group of practitioners. Although the participants represented diverse stakeholder groups across the built environment sector, the study is exploratory and practitioner-informed, and the findings should not be generalised to all Indian construction contexts or to the wider Global South. Instead, the findings should be interpreted as transferable insights that may inform comparable urban housing contexts, subject to further empirical testing. In addition, residents and end-users of social housing were not directly represented. Therefore, socio-economic, equity, and social justice-related linkages should be interpreted as practitioner-derived potential benefits rather than validated resident experiences. Second, the SDG analysis was conducted at the goal and target levels rather than at the indicator level. This was appropriate given the qualitative and exploratory nature of the data, but it does not enable measurement of actual progress against SDG indicators. Third, the SDG alignments were derived from workshop-generated intervention ideas rather than from implemented projects. As such, the findings reflect potential contribution pathways rather than empirically verified sustainability outcomes. Fourth, the time-bounded nature of the workshop may have influenced the depth of participant reasoning, particularly in relation to less familiar SDGs and socio-economic dimensions. Finally, although follow-up interviews provided complementary reflective evidence on CE learning, application, CE-green building interpretation, and implementation barriers, they were not designed to directly validate the SDG associations.

Future research could extend this work by applying the analytical framework to implemented housing projects, enabling comparison between proposed CE strategies and realised sustainability outcomes. Further studies could also examine how different stakeholder groups, such as policymakers, developers, designers, and material suppliers interpret CE–SDG relationships differently. Future research also needs to consider community voices, especially in the case of developing social housing outcomes and how such input influences practitioner views and final project decision making processes. Comparative research across Global South contexts would be valuable for identifying context-specific and transferable pathways for aligning CE with sustainable development priorities. The relationship between CE and GB frameworks can be assessed from a deeper theoretical and conceptual framing in future research. While this study identifies a persistent overlap in practitioner understanding, the conditions under which these frameworks work in complimentary and contractionary fashion, remain insufficiently addressed and is a vital area for built environment sustainability scholarship. Finally, future work could develop indicator-level assessment methods to evaluate how CE interventions in the built environment contribute to measurable SDG progress over time.

Generative AI statement

The author(s) declared that Generative AI was used in the creation of this manuscript. During the preparation of this manuscript, the authors used RMIT University’s Val for the purposes of refining writing and sentence flow. The authors have reviewed and edited the output and takes full responsibility for the content of this publication.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/frsc.2026.1869079/full#supplementary-material

Supplementary material Supplementary material at the source

Footnotes

Edited by: Ka Leung Lok, University of South Wales, United Kingdom

Reviewed by: Andrea Jia, University of Hong Kong School of Professional and Continuing Education, China

Nabil M. Nagy, Military Technical College, Egypt

Mohammadamin Havaei, Iran University of Science and Technology, Iran