Developing a Nature-Inspired Sustainability Assessment Tool: The Role of Materials Efficiency ^†

Abstract

The global push for sustainable development has intensified the need for innovative tools to assess and enhance sustainability in the built environment. This study explores the role of materials efficiency (ME) within a nature-inspired sustainability assessment framework, focusing on green building projects in South Africa. Using a nature-based (biomimicry) approach, this study identifies and prioritises key ME criteria such as eco-friendly materials, local sourcing, and responsible processing. The methodology employed the Analytic Hierarchy Process (AHP), with input from 38 carefully sampled construction experts, to rank ME criteria through pairwise comparisons. The findings revealed that eco-friendly materials (29.5%) and locally sourced materials (25.1%) were the highest-weighted factors, with strong expert consensus (CR = 0.01). The study highlights how nature-inspired principles like closed-loop systems and minimal waste can guide sustainable construction aligned with global goals such as the UN Sustainable Development Goals. The conclusion advocates for integrating ME criteria into green certification systems, industry collaboration, and further research to scale the framework globally. This study bridges biomimicry theory with practical sustainability assessment, offering actionable insights for the built environment.

1. Introduction

The heightened global focus on sustainable development has pervaded diverse sectors, prompting a critical re-evaluation of conventional practices and an urgent need for innovative solutions. Sustainability assessment tools (SATs) have emerged as vital instruments in this endeavour [1], providing frameworks to evaluate the environmental, social, and economic impacts of human activities [2,3]. These tools enable stakeholders to make informed decisions, set targets, track progress towards sustainability objectives, and identify areas for improvement. In the quest for more effective and holistic approaches to sustainability, nature-inspired design has garnered increasing attention as a rich source of time-tested strategies and principles [4]. By observing and emulating the intricate processes and designs found in the natural world, researchers and practitioners are developing innovative solutions to address complex sustainability challenges [5]. Materials efficiency (ME) stands out as a critical element among these nature-inspired concepts. How natural organisms and entities utilise resources with outstanding effectiveness, maximising functionality and minimising waste, offers a profound path to creating a more sustainable human environment and systems. By examining how nature achieves efficiency in its use of materials and how nature principles can be translated into measurable indicators, this research study illuminates the vast potential of nature-inspired ME to enhance the efficacy and scope of the sustainability assessment framework.

When viewed through the lens of sustainability, ME encompasses a multifaceted understanding that extends beyond mere economic and environmental considerations. Several perspectives gleaned from available research highlight the critical dimensions of this concept. ME fundamentally connotes doing more with less, translating directly into cost savings, waste reduction, and maximal resource utilisation [6]. This process involves either manufacturing a product or service using fewer input materials or generating a greater product or service output from the same quantity of material [7]. From an environmental standpoint, ME is pivotal in environmental stewardship. For example, producing new materials is an energy-intensive process and a significant contributor to greenhouse gas (GHG) emissions, accounting for approximately 25% of all anthropogenic CO₂ emissions [8]. Furthermore, materials production generates substantial volumes of waste during a product’s lifecycle [9].

A broader perspective on ME in sustainability involves producing competitive products and services using fewer material inputs and simultaneously minimising harmful environmental impacts throughout the life of a product [10,11]. This perspective further acknowledges the crucial role of consumers in driving demand for material-efficient products and services through their waste-reduction initiatives and purchasing decisions. In industries such as construction, ME can be described as a state of finding ways to minimise waste generation and optimise material usage from a building’s design to demolition. Within the manufacturing sector, ME is understood as the practices and strategies aimed at enhancing the usability of raw materials without compromising a product’s original functions and purpose [12]. In response, nature-inspired solutions have emerged as a transformative approach, leveraging ecological and biological principles to enhance sustainability in building design, materials selection, and resource efficiency. However, despite growing interest in biomimicry and other bio-inspired concepts, there remains a critical gap in standardised assessment tools that quantify the sustainability benefits of nature-inspired ME strategies.

Nature-inspired sustainability assessment tools represent a paradigm shift in evaluating and promoting environmental responsibility. These tools draw inspiration from natural systems’ efficiency, resilience, and interconnectedness to provide a more comprehensive and effective means of assessing human impacts and guiding sustainable development. In the built environment, nature-inspired assessment tools, such as the conceptualised biomimicry sustainability assessment tool (BioSAT), are crafted to aid in the sustainable transformation of buildings and the construction sector [3]. The BioSAT study the principles of nature (biomimicry principles) and provide a framework to guide practitioners and other stakeholders in greening the built environment. Recognising the need for context-specific solutions, these tools often aim to be adaptable to the unique needs of different countries and regions, aligning with global sustainability goals like the UN Sustainable Development Goals (SDGs).

Natural systems have evolved over billions of years, developing remarkably efficient material-use strategies. These strategies, centred around closed-loop cycles, minimal material use, and multi-functionality, offer valuable inspiration for enhancing sustainability in human-designed systems [13]. In nature, resources are constantly recycled, mirroring the circular economy concept. For instance, in a forest ecosystem, plants absorb nutrients from the soil to grow. These nutrients are returned to the soil when they decompose, creating a self-sustaining cycle. Similarly, the oxygen and carbon dioxide cycle between plants and animals and the continuous water movement through evaporation, condensation, and precipitation exemplify nature’s ability to circulate resources without generating waste. Nature also demonstrates remarkable minimal material use. Organisms often utilise lightweight yet strong materials that are frequently sourced locally [5,14,15]. Wood and bamboo should be considered in construction; these natural materials are renewable, biodegradable, and often require less energy for processing compared to conventional materials like steel and concrete.

Furthermore, multi-functionality is a hallmark of natural materials and systems [16]. A single material in nature can often perform multiple tasks sequentially or simultaneously, optimising resource utilisation and enhancing adaptability. For example, plant leaves are responsible for photosynthesis, facilitate gas exchange and water transport, and possess self-cleaning properties [17,18,19,20]. Similarly, the skin of animals provides protection and sensory input and aids in temperature regulation. By studying these natural examples, innovators can gain valuable insight for developing human-made materials with properties such as enhanced functionality, a reduced carbon footprint, and the 3Rs (reduce, reuse, and recycle). Translating the ingenious ME strategies observed in nature into practical metrics for sustainability assessment tools is crucial in fostering more sustainable practices [21]. Figure 1 shows the conceptual metrics translated from nature-inspired principles of ME towards developing a sustainable assessment tool. Hence, this paper explores the influence of ME in developing a comprehensive, nature-inspired, sustainable framework for assessing green building projects in South Africa.

2. Research Methodology

The study aims to develop a comprehensive, nature-inspired, sustainable framework for assessing green building projects. To achieve this aim, this paper specifically explores the role and significance of materials efficiency (ME) within the conceptualised nature-inspired sustainability assessment framework. The framework identifies, examines, organises, and determines the relative importance of the core ME category for evaluating the sustainability performance of buildings in South Africa, which can be adapted globally as well. To achieve the aim of this study, the ME aspect of the framework is assessed. A standardised self-administered pairwise questionnaire survey was administered to active sustainability experts and professionals in the South African construction sector. These respondents include architects, construction project managers, project managers, civil engineers, quantity surveyors, mechanical engineers, industrial engineers, town/urban planners, electrical engineers, and construction managers. These experts/professionals are experienced and registered with their respective professional bodies. They have also executed and participated in green-rated building projects in South Africa. The instructions and explanations preceding the questions were kept simple and clear enough for easy comprehension by the respondents (decision-makers). Figure 2 shows the content and design of the pairwise questionnaire. The experts used the provided Saaty number scale of 1–9 to rate the importance of the items against each other and to allocate weights in pairwise comparisons. Where 9 is extremely important and 1 is equally important, the experts were asked to mark with (X) to determine the relative importance of materials efficiency criteria options A (ME1, ME1, ME1, ME2, ME2, and ME3) on the left column to options B (ME2, ME3, ME4, ME3, ME4, and ME) on the right column. Of the fifty (50) experts/respondents (decision-makers) identified and sampled, a total of thirty-eight (38) completed questionnaires were received and analysed, representing a 76% response rate.

Following the aim of this research study, descriptive analysis and the Analytic Hierarchy Process (AHP) technique of multi-criteria decision-making (MCDM) method were employed. Developed in 1980 by Thomas L. Saaty, the AHP is a mathematical tool/model based on a hierarchical structure for managing quantitative and qualitative multi-criteria elements involved in decision-making behaviour [22]. To employ AHP, Saaty [23] listed six (6) steps to follow, namely, define the problem, develop the AHP hierarchy, perform the pairwise comparison, estimate the relative weights, check the consistency, and obtain the overall rating. A descriptive analysis of the 38 responses was conducted using an Excel spreadsheet. At the same time, the remaining sections were aggregated using a Goepel Excel spreadsheet and further analysed using Super Decisions V3 for AHP. Super Decisions v3 software was used for the experts’ analysis, synthesis, and justification of inputs. The AHP method in this research study was executed based on the summarised steps in the following order: build a hierarchy, make comparisons, calculate weights, check consistency, and produce results.

3. Findings and Discussions

From the demographic background of the respondents, the majority (expert decision-makers) possess a master’s degree, representing 65.8%, followed by those with a PhD/doctoral degree, representing 28.9%, and those with a bachelor’s/honours degree, representing 5.3%. The distribution of the respondents according to their profession showed that 26.3% of the respondents (expert decision-makers) are architects, 18.4% are quantity surveyors, 13.2% are construction managers and construction project managers, and 5.3% are civil engineers, electrical engineers, mechanical engineers, project managers, and town/urban planners. In comparison, 2.6% of respondents represent only industrial engineers. Sample distribution according to the employers showed that 57.9% of the respondents (expert decision-makers) have worked in the construction industry for 11–15 years, while 21.1% have worked in the industry for 6–10 years and 16–20 years. Based on the number of green-certified projects completed, 65.8% of the respondents (expert decision-makers) have been involved in 3–4 projects, 31.6% in 1–2 projects, and 2.6% in 5–6 projects.

The code definition of the identified materials efficiency criteria is as follows: ME1 (responsible materials processing), ME2 (use of locally sourced materials), ME3 (use of materials with verifiable eco-labels), and ME4 (use of eco-friendly materials). Thirty-eight (38) responses were received from the experts, and their judgements were aggregated using the geometric mean method (combining judgements in a comparison matrix).

Table 1. Aggregated pairwise comparison for materials efficiency criteria matrix.

Categories	ME1	ME2	ME3	ME4
ME1	1.00	0.95	0.95	0.75
ME2	1.05	1.00	1.11	0.89
ME3	1.05	0.90	1.00	0.75
ME4	1.33	1.13	1.33	1.00

presents all resulting collective judgements for pairwise comparison as calculated and mapped into a single decision matrix. The eigenvalue approach was employed to determine the subjective weight of each element in the matrix. The normalised principal right eigenvector of the ME criteria matrix that is calculated represents the relative weights of the elements, which sum up to 1.0. W represents the normalised eigenvector and is calculated using Equation (1) below. According to Al Barqouni [24], the mathematical process of obtaining the relative weights (W) of matrix A is as below:

A × W = λmax × W

(1)

Table 2. Aggregated pairwise comparison for materials efficiency criteria matrix showing priorities.

Categories	ME1	ME2	ME3	ME4	Priority (W)	Rank
ME1	1.00	0.95	0.95	0.75	0.22591	4
ME2	1.05	1.00	1.11	0.89	0.25060	2
ME3	1.05	0.90	1.00	0.75	0.22843	3
ME4	1.33	1.13	1.33	1.00	0.29506	1
λmax = 4.002; CR = 0.01; CI = 0.00; RI = 0.90

presents the weights for the pairwise comparison matrix, showing values for the consistency ratio (CR), λmax (the biggest eigenvalue of the criteria matrix), the consistency index (CI), and the random index (RI). Since the number of elements (n) is 4, which ideally is the rounded value of λmax [25], the RI is fixed and will be 0.90 according to the random index table by Saaty and Vargas [26]. For the judgement matrix to be deemed consistent, acceptable, and valid, the value of CR should be less than 0.10 or 10% [22,27]. The results of the combined judgements and eigenvector values (priority weightings) are presented in Table 2. The table shows that the use of eco-friendly materials criteria (ME4) has the highest priority weighting under the ME category in the conceptualised comprehensive, nature-inspired, sustainable framework for assessing green building projects at 0.295, followed by the use of locally sourced materials criteria (ME2) with a priority weight of 0.251 and the use of materials with verifiable eco-labels (ME3) with a priority weight of 0.228, while the least priority weighting of 0.226 is for the responsible materials processing criteria (ME1). Since the consistency ratio of the matrix (CR = 0.01) is less than 0.10, this implies that the experts were consistent in answering the pairwise questionnaire. The judgement matrix is therefore deemed consistent, and the results are satisfactory.

The weights of the ME criteria were rounded to the nearest integer for simplicity and practical use [28]. From Figure 3, it can be inferred that the use of the eco-friendly materials criteria (ME4) contributes the highest weighting of 30% to the goal (materials efficiency category), the use of locally sourced materials criteria (ME2) contributes 25%, and the use of materials with verifiable eco-labels (ME3) contributes 23%. In comparison, the least contribution of 23% was attributed to the responsible materials processing criteria (ME1).

The relationship between ME and an effective nature-inspired sustainability assessment tool (SAT) was statistically significant, with a consistency ratio of 0.01 or 0.1%. The research study generally hypothesised that the ME category influences an effective nature-inspired SAT. A descriptive assessment of the latent variables (criteria) of the ME category revealed that the experts/decision-makers perceive that all the variables will significantly influence the sustainability performance of nature-inspired SAT in the South African construction industry. The high relative importance of the weighting of the variables and the ME category by the experts (respondents) suggests their significance. At the same time, the consistency ratio value below 0.1 or 10% indicates the validity of the result. According to Koltun [29], materials are key tools for pushing progress towards sustainable development. Similarly, the key role of ME is significant for sustainable development in European countries [30]. However, the natural environment offers vast opportunities and insights for ME to be achieved.

4. Conclusions and Recommendations

The study presents a groundbreaking approach to sustainability assessment in the built environment by integrating nature-inspired principles, particularly materials efficiency (ME), into a comprehensive framework for evaluating green building projects in South Africa. By leveraging biomimicry (nature principles), the research underscores how natural systems characterised by closed-loop cycles, minimal material use, and multi-functionality can potentially inform sustainable construction practices. The Analytic Hierarchy Process (AHP) analysis revealed that eco-friendly materials (ME4, 29.5% weighting) and locally sourced materials (ME2, 25.1%) are the most critical criteria, highlighting their pivotal role in reducing environmental impacts while maintaining functionality. The consistency ratio (CR = 0.01) validated the robustness of expert judgements, affirming the reliability of the proposed framework. The findings align with global sustainability goals, such as the SDGs, and demonstrate the potential for nature-inspired strategies to bridge the gap between theoretical biomimicry and practical applications in construction. However, the study also identifies gaps, including the lack of standardised tools to quantify nature-inspired ME benefits and the need for broader stakeholder engagement to drive adoption.

The study recommends leveraging digital technologies and tools to optimise and simulate nature-inspired innovations, ensuring measurable sustainability outcomes. The expansion and robust funding of research exploring the framework’s scalability in different socio-economic and climatic contexts should be supported. To enhance awareness and education, it is also recommended that professional bodies and higher education institutions incorporate biomimicry and sustainability principles into the curricula to foster innovation. Stakeholders’ collaboration to prioritise locally sourced and eco-friendly materials with genuine eco-labels should also be promoted.