To operationalise the evaluation of IS solutions within the MCDA framework, the SYMBA methodology adopts a readiness-based indicator system. The use of readiness levels allows the assessment of IS solutions not only in terms of their potential benefits, but also according to the conditions required for their effective implementation, continuity, and replication. This approach recognises that the success of IS initiatives depends on a combination of technical, environmental, organisational, regulatory, and societal factors.

As illustrated in Figure 1, the SYMBA framework is structured around five complementary readiness dimensions: Symbiosis Readiness (SymRL), Environmental Readiness (ERL), Organisational Readiness (ORL), Legal and Ethical Readiness (LRL), and Societal Readiness (SRL). Together, these dimensions provide a holistic representation of IS maturity, capturing both the core characteristics of symbiotic exchanges and the enabling conditions that support their deployment in real-world contexts.

Figure 1.

Readiness levels used in the MCDA

SymRL represents the core dimension of the framework and reflects the extent to which an IS solution achieves effective and stable integration of resource exchanges. This readiness level captures the maturity of the symbiotic relationships themselves, considering aspects such as the technical feasibility of exchanges, the integration of material, energy, or water flows, and the coherence of the overall system configuration [10].

Given its central role, SymRL is assessed using a more granular scale than the other readiness dimensions. The evaluation criteria and scoring levels used to assess SymRL are presented in Table 1, which outlines progressive stages of symbiotic maturity, from early conceptualisation to fully operational and replicable solutions. This differentiation allows the framework to distinguish between IS initiatives that are still exploratory and those that demonstrate consolidated, system-level integration.

While SymRL captures the core functionality of IS solutions, successful implementation also depends on a set of enabling conditions addressed through four complementary readiness dimensions.

ERL evaluates the extent to which an IS solution delivers environmental benefits and aligns with sustainability objectives [11]. This includes considerations related to resource efficiency, emissions reduction, and contribution to circular economy goals. The criteria and scoring levels for ERL are summarised in Table 2:

ORL reflects the capacity of the involved actors to manage, coordinate, and sustain IS activities over time. This dimension captures aspects such as governance structures, coordination mechanisms, and organisational capabilities required to support symbiotic exchanges [12]. The corresponding evaluation criteria are presented in Table 3.

LRL addresses the regulatory and normative context in which IS solutions operate. This includes compliance with existing legislation, legal feasibility of resource exchanges, and alignment with ethical and safety considerations [12]. The criteria used to assess LRL are detailed in Table 4, ensuring that regulatory constraints and ethical considerations are explicitly accounted for in the evaluation.

SRL focuses on social acceptance, stakeholder engagement, and broader societal implications of IS solutions [13]. This dimension captures factors related to public perception, stakeholder support, and social value creation. The assessment criteria for SRL are provided in Table 5:

Together, the five readiness dimensions form an integrated indicator system that supports consistent and transparent evaluation of IS solutions. Rather than assessing individual aspects in isolation, the readiness framework acknowledges that IS maturity emerges from the interaction between technical integration and contextual readiness. The use of differentiated scoring scales allows the framework to capture varying degrees of maturity while maintaining comparability across solutions.

The scoring of the readiness indicators was based on a structured qualitative–quantitative assessment combining available project data and expert judgement. Specifically, each IS solution was evaluated using information derived from the SYMBA mapping exercise and associated documentation, including technical descriptions, implementation status, and contextual conditions [14]. Where direct quantitative data were not available, scores were assigned through expert-based evaluation guided by predefined criteria to ensure consistency across cases. As such, the resulting scores should be interpreted as indicators of relative readiness and maturity rather than precise measurements of environmental or economic performance.

The SYMBA MCDA methodology follows a stepwise process that translates the evaluation of individual readiness dimensions into a single composite score for each IS solution (Figure 2). First, each solution is assessed independently against the defined readiness levels, resulting in a set of criterion-specific scores. These scores reflect the degree to which a solution meets the requirements associated with each readiness dimension, based on available information and expert judgement.

Figure 2.

MCDA methodology with steps for its development

Second, weighting factors are applied to each readiness level to represent their relative importance in the overall evaluation. The weighted scores are then aggregated to compute a single composite score for each IS solution. This aggregation enables direct comparison across solutions while preserving the contribution of each individual criterion.

Finally, composite scores are interpreted using predefined maturity ranges that classify IS solutions into three categories: beginner, intermediate, and advanced. This classification supports a shift from purely comparative ranking towards a more actionable assessment, as it links evaluation results to targeted recommendations for improvement, scaling, or replication.

The MCDA framework was implemented consistently across all evaluated IS solutions, ensuring methodological coherence and comparability.

The weighting process began with an internal expert consultation exercise aimed at capturing informed perspectives on the relative importance of the readiness dimensions used in the MCDA framework. This internal step was designed to reflect expert knowledge on IS evaluation and to contribute one of the two complementary inputs to the overall weighting process.

Internal stakeholders involved in this exercise represented expertise in industrial symbiosis implementation, circular economy strategies, sustainability assessment, and decision-support methodologies. Their input was collected through a combination of collaborative discussions and a structured survey-style consultation. First, a joint meeting was held to introduce the readiness framework, clarify the interpretation of each dimension, and ensure a shared understanding of the evaluation scope. This was followed by an individual consultation in which participants assessed the relative importance of the readiness dimensions by assigning weights according to their expert judgement.

The resulting internal weighting factors express a consolidated expert perspective on the key dimensions influencing the maturity and feasibility of IS solutions. The outcomes of the internal weighting exercise were subsequently considered alongside input from external stakeholders. The following subsection describes the external stakeholder consultation process used to complement and broaden the weighting of the readiness dimensions.

External stakeholder engagement was conducted through a structured, two-step process combining an online questionnaire with a subsequent interactive workshop (Figure 3). First, an online questionnaire was distributed to external stakeholders representing academia, industry, public authorities, and civil society reflecting a quadruple-helix perspective, [15]. The questionnaire was designed to capture expert judgement on the relative importance of the defined readiness levels using two complementary approaches: a ranking exercise, in which participants ordered the readiness dimensions according to perceived importance, and a weighting exercise, in which participants assigned relative weights to each dimension.

Figure 3.

Steps for round 2 of stakeholder consultation

The responses to the questionnaire were aggregated and analysed to derive preliminary external weighting factors. These preliminary results were then used as input for an online co-creation workshop, where stakeholders collectively reviewed, discussed, and interpreted the outcomes of the questionnaire. The workshop provided an opportunity to clarify differing perspectives, validate the consistency of the results, and refine the weighting scheme through discussion and consensus-building. The final external weighting factors were defined based on this combined quantitative and qualitative process, ensuring alignment between individual expert judgement and shared stakeholder understanding.

Following the completion of both weighting rounds, the internal and external weighting outcomes were jointly analysed to identify convergences and differences in the relative importance assigned to the readiness dimensions. On this basis, a consolidated set of weighting factors was defined, integrating expert knowledge and external stakeholder perspectives into a single weighting scheme used in the MCDA application.

Taken together, the internal and external stakeholder consultations described above provided two complementary perspectives on the relative importance of the readiness dimensions used in the MCDA framework. Rather than treating one input as a validation of the other, the SYMBA methodology integrates expert knowledge and broader stakeholder perspectives to derive a balanced and transparent weighting scheme. This combined approach enhances the legitimacy and robustness of the weighting process while ensuring that the resulting priorities reflect both technical considerations and contextual values. The final set of weighting factors derived from this process constitutes a core input to the subsequent application of the MCDA framework, where they are used to evaluate, prioritise, and interpret the maturity of IS solutions.

The SYMBA MCDA framework was applied to a dataset of over 150 IS solutions identified across Europe as part of the project’s systematic mapping activities [14]. The solutions encompass a wide range of sectors (agri-food, plastic and packaging, textile, waste and wastewater valorisation) and bio-based industrial ecosystems which were classified into three main categories according to their operational nature: approaches, methodologies, and platforms. This classification captures systematic differences in governance structures, coordination mechanisms, and typical levels of technological maturity, thereby enabling comparative analysis across heterogeneous IS initiatives.

The mapped solutions address diverse forms of resource exchange, including material by-products, energy, water, infrastructure, and shared services. The mapping exercise thus provided the empirical basis for applying the MCDA and testing its capacity to differentiate solutions according to their readiness and maturity. Each solution was evaluated using a structured set of readiness indicators, based on available project data and expert-informed assessment following the criteria defined in the methodological framework section.

The application of the MCDA framework resulted in composite scores for each IS solution, derived using a stakeholder-informed weighting scheme and used for prioritisation and maturity classification. The final weighting factors assigned to the five readiness dimensions are summarised in Table 6, reflecting the integration of internal expert input and external stakeholder perspectives.

SymRL emerged as the most influential criterion in the composite evaluation, reflecting its central role in determining the technical and systemic feasibility of IS solutions. ERL was assigned the second-highest weight, underscoring the importance attributed to environmental performance and circularity outcomes. ORL and LRL occupied intermediate positions in the final weighting scheme, indicating their relevance as enabling conditions for implementation. SRL, while consistently weighted lower, remained an integral component of the evaluation framework.

These results highlight both convergence and nuance in stakeholder priorities. While the overall hierarchy of readiness dimensions was broadly consistent across stakeholder groups, differences in emphasis were observed, particularly with respect to environmental and organisational considerations. Such variations underline the value of incorporating multiple stakeholder perspectives within the MCDA framework.

Using the final weighting factors, composite scores were calculated for each IS solution using Equation (1), where individual readiness scores were aggregated into a single indicator of overall maturity.

where X is the score of each readiness level, Y is the weight given by the MCDA method, and α is the final value for each readiness.

These scores enabled the ranking and prioritisation of solutions within and across the three solution categories. Rather than relying solely on ordinal rankings, the results were further interpreted through a maturity-based classification that groups solutions into three levels: beginner, intermediate, and advanced (Figure 4).

Figure 4.

Recommendations based on maturity

Beginner solutions are characterised by low composite scores (lower than two) and typically exhibit significant gaps in one or more readiness dimensions. These solutions often correspond to early-stage initiatives or concepts that require foundational development before scaling can be considered. Intermediate solutions (scores between two and four) demonstrate more balanced readiness profiles, with functioning symbiotic exchanges but identifiable weaknesses that may constrain broader deployment. Advanced solutions (scores higher than four) achieve high scores across most readiness dimensions and are generally suitable for replication, scaling, or transfer to new contexts.

A cross-case analysis of the evaluated solutions reveals several consistent patterns. Solutions classified as platforms tend to achieve higher scores in symbiosis and organisational readiness, reflecting more advanced coordination mechanisms and established stakeholder networks. In contrast, approaches and methodologies generally exhibit lower levels of implementation maturity, often remaining at conceptual or pilot stages. Environmental readiness scores are relatively high across most cases, indicating strong potential for resource efficiency improvements, while legal and societal readiness dimensions show greater variability, suggesting that regulatory conditions and stakeholder acceptance remain context-dependent factors. These patterns highlight the uneven development of IS solutions across different dimensions and reinforce the need for multidimensional evaluation frameworks.

Beyond prioritisation, the SYMBA MCDA framework was designed to inform action. For each maturity category, a set of indicative implementation guidelines was derived based on the readiness dimensions contributing most strongly to the composite score. These guidelines aim to support stakeholders in identifying targeted actions to improve readiness and advance solutions along the maturity spectrum.

In this context, the prioritisation outcomes highlight the central role of symbiosis-related and environmental considerations in shaping stakeholder perceptions of the feasibility of IS solutions. At the same time, the intermediate weighting assigned to organisational and legal dimensions underscores their function as enabling conditions rather than primary drivers of implementation. Taken together, these patterns reinforce the view that successful IS deployment depends on a combination of robust technical integration and supportive institutional contexts.

For beginner solutions, recommendations focus on building foundational capacities, such as strengthening organisational structures, clarifying regulatory conditions, and engaging key stakeholders. Intermediate solutions are encouraged to address specific readiness gaps, improve coordination mechanisms, and seek targeted support to enhance robustness and scalability. For advanced solutions, guidance emphasises replication, formalisation of partnerships, and integration into regional or sectoral strategies.

These findings are consistent with previous studies highlighting governance, economic, and regulatory barriers as key constraints to the implementation of industrial symbiosis. Henriques et al. [16] discuss sector-specific barriers, whereas Södergren and Palm [5] underline the importance of local governance and institutional conditions.

By linking evaluation results to practical guidance, the framework reinforces its role as a decision-support tool rather than a purely analytical exercise. This feature is particularly relevant for policymakers, cluster managers, and funding bodies seeking to allocate resources effectively and support the strategic development of industrial symbiosis initiatives.

The SYMBA framework contributes to the growing body of decision-support tools for industrial symbiosis by operationalising a stakeholder-driven MCDA approach that integrates multiple readiness dimensions into a coherent evaluation model. A key methodological strength lies in the use of readiness levels as structured indicators that support both comparison and diagnosis. By translating qualitative and quantitative information into comparable scores, the framework enables systematic prioritisation while preserving transparency regarding the factors driving overall performance. Furthermore, the maturity-based interpretation of results moves beyond simple ranking, allowing stakeholders to understand not only which solutions perform better, but also why they do so and what actions may be required to improve readiness.

Compared to existing MCDA applications in sustainability, Bystrzanowska [8] notes the reliance on predefined indicator structures and analyst-driven evaluation processes. More recent studies, such as Caruso [9], incorporate multiple sustainability dimensions but continue to depend primarily on expert-defined weighting schemes. In contrast, the SYMBA framework introduces a combined readiness-based indicator system and a participatory weighting process integrating both internal and external stakeholder perspectives, thereby enhancing both the diagnostic capacity of the framework and the legitimacy of the prioritisation outcomes. The observed weighting patterns reflect shared priorities while also capturing nuanced differences linked to organisational, legal, and societal contexts. This approach addresses well-recognised challenges in sustainability-oriented MCDA applications, particularly regarding the transparency and justification of weighting choices and the integration of stakeholder preferences [17].

From a governance and decision-making perspective, the results highlight the potential of the SYMBA framework to support strategic planning across different stages of IS development. By linking prioritisation outcomes to maturity-based interpretation, the framework enables stakeholders to move beyond static rankings and focus instead on identifying development pathways tailored to the readiness profile of each solution. This feature is particularly relevant for policymakers, regional authorities, and funding bodies seeking to allocate resources effectively and design support measures aligned with the maturity and needs of IS initiatives.

At the same time, the application of the framework reveals inherent limitations associated with readiness-based evaluations. While the approach provides valuable insights into implementation conditions and maturity, it does not replace detailed quantitative assessments of environmental or economic performance. Rather, the results underscore the complementary role of the SYMBA framework alongside tools such as life cycle assessment or cost–benefit analysis.

Importantly, addressing this limitation constitutes a core next step of the SYMBA project. Building on the prioritisation results presented in this study, subsequent project activities aim to integrate the MCDA framework with environmental, economic, and circularity assessment tools. This integration is intended to enable a more comprehensive evaluation of selected IS solutions, combining readiness-based prioritisation with quantified sustainability performance and thereby strengthening the robustness and applicability of decision-support for implementation, scaling, and replication.