Including Nature-Based Success Measurement Criteria in the Life Cycle Assessment

Abstract

Conventional life cycle assessment (LCA) is a technique to assess environmental impacts associated with all the stages of a product’s life or process. Such impacts along the product life or process are assessed via criteria to establish success when accounting for resource intake, waste, and emissions fluxes. In most cases, the assessment range may vary, defined by the designer’s and product’s aims, failing to evaluate all parts of the said cycle completely. This before is said to follow the “reducing unsustainability” paradigm (RUP), and changes are needed toward an assessment based on the “achieving sustainability” paradigm (ASP). Thus, this chapter embarks on the search for assessment approaches, assuming biomimicry principles can improve current LCIA tools. Comprehending the LCA criteria to assess product or process impacts is done via a literature review. Results showed that most assessment tools continue to be developed under the RUP, where three approaches present great potential for an ASP. A discussion over the difference in assessing two case studies in the built environment, net-zero-energy buildings, and sustainable construction projects under both paradigms is presented.

1. Introduction

The life cycle assessment (LCA) method aims to assess the product or process’s environmental impact along its life cycle [1, 2, 3]. This technique or tool focuses mainly on evaluating the contributions that the use of a product or execution of a process has to the overall environmental load. This evaluation may be of help for improvements of the product or process [1]. However, it has been highlighted that LCA works under the premise of “reducing unsustainability” using common indicators to achieve a so-called “eco-design” [4].

Among the four stages found in the ISO14040 guidelines, the LCA starts defining how much of the product life cycle will be evaluated along with the specific purpose of the evaluation. This stage is followed by resources’ flux balances, that is, material flux, energy flux, of the product or process and its interaction with the environment, for example, emissions and raw materials consumption. From such resources’ flux balances, an inventory analysis is conducted by following a set of indicators belonging to or distributed among various categories. The latter is arranged hierarchically with respect to the impact importance using weighting. The LCA finishes with a critical review of results and results presentation [1, 5].

Measuring a product’s life cycle to reduce unsustainability intends to reduce its environmental impacts, but this may not help create sustainability [4] of the product or process because their continuity is yet to be considered, along with the conditions that assure the need for that product or process. In turn, the product or process assessment toward improvement needs to be based on achieving sustainability rather than reducing the negative impacts on the environment [4].

Assessment measures toward improvement based on achieving sustainability have been argued to be needed, where the design approaches, cradle-to-cradle, and biomimicry, are the closest aligned with sustainability achievement, aiming at creating beneficial impacts [4].

Thus, accounting for the previously presented arguments, does the conventional LCA method need a revision to change the paradigm? (i.e., achieving sustainability, Figure 1). Could the biomimicry philosophy help improve the current LCA method?

Figure 1.

Representation of a life cycle highlighting the inventory fluxes (inputs in blue, outputs in red) and impact assessment stages. Biomimicry principles (in pink) could act as an assessment complement toward developing a tool that evaluates sustainability achievement.

These two questions have led to a comprehensive yet systematic review based on a combination of keywords framed in the specific topic. Thus, the first keyword combination is Biomimicry AND (“life cycle assessment” OR LCA) on the Google Scholar database, without year restrictions. This keyword combination search yielded 2600 results. The same search in the ScienceDirect database yielded 216 results, among which 34 results were irrelevant documents such as part of books, for example, index and foreword.

This systematic literature search was analyzed using the VOSviewer software [6] to examine current research trends. Based on 210 documents, network, and overlay visualization maps are constructed using a compiled .ris file with the metadata of each document. Such maps can be created by using two approaches key terms in the keywords section from each research article or key terms in the title and abstract of each document, both based on a minimum threshold of occurrence of the key terms. The following observations can be drawn from the maps presented in Figures 2–4.

Figure 2.

Overlay representation of the keyword occurrence approach, using the minimum occurrence threshold (16).

Figure 3.

Overlay representation of the keyword occurrence approach, using an occurrence threshold of two.

Figure 4.

Overlay representation of the keyword occurrence approach, using an occurrence threshold of one.

When using the recommended minimum threshold by the software algorithm, based on the occurrence of the keywords, the overlay visualization (Figure 2) presents the term “biomimicry.” This term does not disappear for any minimum threshold in the keywords’ occurrence approach. The contrary happens when the terms in the title and abstract are employed until the threshold is lower than six.

Nevertheless, in both approaches, the term “biomimicry” appeared as a topic of losing interest, that is, this term is not included as part of the titles, abstracts, and keywords in documents after 2016. That was seven years ago. The same appeared to happen with the term “biomimetics.” This is worth mentioning because the interchangeability of both terms is still mistakenly employed among researchers, architects, and designers using nature as a source of inspiration. A clear and straightforward analysis of similarities and differences can be found in [7, 8].

Conversely to the no-use of the terms “biomimicry” and “biomimetics,” the prefix “bio” is frequently spotted in recent documents (color yellow), which actually is intended to be referred to the same perspective as “inspired by nature.” This indicates that cautiousness is still prompted to use the most meaningful terms when asking to what extent you are letting the design be inspired by nature: “biomimicry” or “biomimetics.” Attention should be paid to this issue since a design solution “biologically inspired” does not intrinsically imply that the design solution is “nature-based” (Figure 5) because the former is embedded within the definitions of nature-based solutions [9]. In addition, the use of the term “biomimetic system” was recently coined by the International Standard Organization (ISO) 18,458:2015 (recently reviewed and confirmed in 2021) [10], which claims: “… If a technical system is subjected to a development process according to this International Standard, then it is allowed to be referred to as a ‘biomimetic’ system” [10].

Figure 5.

Proposal for providing understanding and connections among the terms involved in the methods and processes using biological analogies (adapted from [9]).

Moreover, specifically to the keyword occurrence approach (Figures 2–4), three terms appeared as having higher relevance in descending order: “circular economy,” “sustainability,” and “biomimicry.” This tendency is also presented regarding timeline interests (Figures 2–4). On the other hand, the keyword “LCA” or “life cycle assessment” is not as frequently spotted as expected for a literature search based primarily on these keywords. Although this is before, it is interesting to observe how closely these two keywords are to the keyword “circular economy” based on a timeline interest (Figures 2–4, in yellow). This shows the elevated attention paid to economic aspects, which is highlighted by other keywords in recent documents (in yellow): “circularity,” “circular bioeconomy,” “circular business model,” “business model,” “construction sector” (one of the most important contributors to the global economy), and “land use,” and “… material.” Regardless, the most frequent keywords “circular economy” and “sustainability” (Figures 2–4) are part of the objectives for which a designer carries out a LCA whether the scope of the assessment is the environmental, social, or economic impact of the product or process throughout its life cycle.

2. LCA as known today

This section first introduces the theoretical knowledge about the life cycle assessment methods and finishes with the measurement criteria. The LCA method can help designers to account for and analyze the environmental impact caused by the product or process on the environment throughout their entire life cycle. This analysis includes the effect of the inputs required (i.e., resources) and consequent outputs (e.g., emissions) of such products or processes [2].

Considering that the CLCA method has a flexible component that allows the designer to concentrate on evaluating the product or process for a specific purpose, three levels of assessment can be encountered in the literature [11]: conceptual, simplified, and detailed. The following subsections give more details about such levels, phases, and variants found in the literature.

2.1 LCA variants

Since the first implications of setting up a method to evaluate the environmental impacts of a product or process in the 1960s, many improvements have been intertwined with its original concept definition, looking to continue to take advantage of its benefits. Nevertheless, limitations have been presented since the first implementation of the LCA, for example, listed in [12]. Two of those limitations concern the research questions of this chapter: weighting and other aspects of sustainability (economic and social). In this matter, many variants of the LCA can be found in the literature, which copes with the two limitations. For instance, studies focusing efforts on combining these two limitations are: the life cycle sustainability assessment (LCSA) [13], life cycle impact assessment (LCIA) [14], and an LCA + C2C but accounts for the three pillars of sustainability [15]. Other variants are economic life-cycle costing [3], the social LCA (SLCA) [16], dynamic LCA [17], and positive sustainability performance (PSP) [13].

Moreover, attributional LCA (ALCA) and consequential LCA (CLCA) [18] are said to be two approaches to the LCA [5]. The former relates strongly to the evaluation of a system’s specific impact or optimization potential, recommended for micro-level (or local scale) [18]. The latter relates to the impact that a change on a system could have or the increase in demand for such system’s function or product, recommended for meso/macro level (or regional/global scale) [18].

Specifically, in the built environment, the ALCA is the dominant system boundary selected, following the EN15804 (or EN15978) [19], shaping most policy decisions on buildings regarding environmental and climate aspects [18].

2.2 LCA phases and impact assessment criteria

The effect of the inputs and output on the environment can be quantified by the LCA method in different ways because it may vary with the field of application, the first phase of its methodology being the establishment of the objective and scope [20]. However, all products and processes may share the same inputs and outputs. For the former, the inputs are raw materials, water, energy, and chemical resources [2]. For the latter, the outputs are products, co-products, solid waste, and emissions in the air, water, and soil [2]. Detailing every aspect of these inputs and outputs is referred to as the life cycle inventory (LCI) inventory analysis, where they are quantified throughout their life cycle after their identification. Specifically, compiling an LCI starts with process analysis, or a bottom-up approach, where the product system analyzed is broken down into a series of processes representing the life cycle of a product. This is followed by an environmentally extended input-output analysis or a top-down approach rooted in macroeconomics. Finally, a hybrid analysis involves combining the previous two approaches. Each approach requires modeling a system using specific production processes or entire economic systems [21].

The effect of such input harvesting and outputs on the environment are normally measured at different scales: local, regional, and global [2], but also through various forms. This part represents the life cycle impact assessment [22] and is based on the results of the LCI [20]. Among these forms of effect quantification or measurement are cradle-to-grave [ref], cradle-to-gate [ref], gate-to-gate, and the cradle-to-cradle [ref], also referred to as main boundaries for LCA [12] (the limits in which the analysis is performed).

For these different scales of effects, the LCA is known to measure them [2, 23] by using footprint measurements, for example, carbon [24], water [25] (ecological footprint [26] when combined with carbon), and energy. Besides, acidification [27], eutrophication [28], ozone depletion potential [29], photochemical oxidation potential [30], smog, depletion of biotic and abiotic resources, land use, and damages such as ecotoxicity [31], and human toxicity.

In literature, these effects are categorized by the approach used to describe the environmental mechanism of impact depending on the LCI output [23]: midpoint (problem-oriented or classical) and endpoint (damage-oriented) approaches. The former concerns phenomenon-based environmental issues [32], while the latter concerns environmental impacts leading to damage [23]. The main difference between these two approaches is based on the level of uncertainty associated with indicators’ calculation regarding the environmental mechanism related to the environmental issue (for the midpoint approach), and to the prompting of the damage, in context (in the endpoint approach) to human health, ecosystems, and resources availability [33].

All these measurement criteria in the LCA method, specifically in the impact assessment phase, can also be assessed via software such as SimaPro [34], GaBi [35], Umberto [36], One Click LCA [37], and OpenLCA [38].

For impact assessment in the life cycle, several methods can be found in the literature (an overview of each is provided in [23]): Eco-indicator’99, CML 2001, EDIP 2003, EPS 2000, EPD 2007, Ecological Scarcity 2006, Impact 2002+, Recipe, TRACI, Ecological Scarcity Method, Single indicator methods such as ecological and carbon footprints, ILCD 2011, and USEtox.

As the last step of the LCA methodology, there is the interpretation of the scope and objective, inventory, and impact analysis, in order to recognize and address environmental, health, and resource consumption pressures [39].

Moreover, the cradle-to-cradle life cycle approach is aligned with circular economy objectives. For a building, it is the process of carrying out the construction and the building itself [40]. Briefly, this would be divided into four phases [41, 42]: product, construction, use, and end of life, but a more detailed approach it can be given in the product and use phase [40].

Defining the process and factors, it would be as follows:

• Product: related to the initiation and design for construction [40], it considers the materials and their supply, the manufacturing behind, and the management services, where transportation is included [41, 42]. Its main quantitative factors are the coal included in extraction, manufacture, diligence, and disposal of materials, the inputs in relation to energy and water, and the waste outputs [43].

• Construction: execution of construction (transport, construction itself, and installation) [41] and implementation of the necessary measures to mitigate negative impacts [40]. At this stage, the inputs are water and energy, which generally has a significant waste impact [43].

• Use: is the focus of impact and conditions of use [42], where the findings of its maintenance will consequently involve replacement and refurbishment actions [41].

• End of life: refers to cases where the building has demolition as well as the ease of reuse and recycling [42, 43]. All outputs of the process are considered for utilization and quantified in a process called benefits and burdens beyond the system boundary [42].

Although a design phase is not included in the literature in terms of inputs and outputs, it has been placed by the relevance of the planning strategy, concept, and technical design [42]. It allows maximizing results, evaluation of costs, benefits, and combination of designs [40], providing greater inclusion of practices in the process, advancing more toward efficiency than only mitigating impacts. This is why beyond including a social and economic life cycle [44], to complement a focus on sustainable totality, the limits of improvement toward efficiency, innovation, decision, and compliance with circular economy must be addressed, where the inspiration in nature can provide opportunities. Hence the following section shows an analysis of the literature using nature as inspiration for the specific chapter topic.

3. Nature moto as a source of inspiration

Forms, behaviors, and processes in nature have been a source of inspiration for many innovative approaches for products, systems, and process designs, for example, bionics, biomimetics, and biomimicry, in different stages of corporate sustainability (compliance and business-centered, systemic, and regenerative and co-evolutionary, respectively) and worldview (technocentric, mixed, and eco-centric, respectively) [7]. The approach cradle-to-cradle is a regenerative design approach based on biomimicry principles, that is, use materials sparingly, use energy efficiently, do not exhaust resources, sources or buy locally, optimize the whole rather than maximize each component individually, do not pollute your nest, remain in dynamic equilibrium with the biosphere, using waste as a resource, diversify and cooperate, and be informed and share information [45].

3.1 Improving impact assessment

Almost a decade ago, it was argued that no impact assessment method had been developed for biomimicry and that current ways of impact assessment followed a “reduced unsustainability” paradigm instead of following an “achieving sustainability” paradigm [4]. This “achieving sustainability” paradigm is not entirely opposed to the conventional way of performing impact assessment. However, these paradigms differ from each other as follows [4]:

1. While the conventional paradigm considers all potentially harmful impacts, the new paradigm considers all impacts in context.

2. Instead of comparing the product characteristics with other products, it is proposed to assess the product against sustainability conditions. Such assessment needs designers to distinguish between “what is” and “what is not” sustainable. For example, if a product has a characteristic that is beneficial to various aspects of the indoor environment but is not to one aspect of human life, the product would not be considered as having a beneficial impact.

3. Contrary to assessing progress, it is proposed to evaluate “achievement” in the sense of whether the target design characteristics are met. In this way, for instance, instead of focusing on developing systems, products, or processes to help reduce energy consumption from fossil fuels, the target is considered to function with an alternative energy source.

Having a beneficial impact, here, refers to the impact on the environment contributing to the regeneration of that environment toward a sustainable state [4]. Internalizing such a new paradigm helps enlighten how the impacts are assessed, highlighting the product benefits to sustainability’s environmental, social, and economic aspects.

Recent studies found in the literature present potential to materialize such a new-paradigm-based tool based on biomimetics [46], on biomimicry [40], and on cradle-to-cradle (C2C, also known as regenerative design approach) [15]. These studies followed the ten biomimicry principles [45]. Table 1 presents a comparison of these three approaches.

Achieving sustainability paradigm [4]			LCA	Potential impact assessment tools
			Conventional and current variants	BiomiMETRIC,; 2019 [46]	LCA + C2C,; 2021 [15]	Biocircular model,; 2021 [40]
Constituents		Description
Life cycle approach		Analyzing each step in the life of a product, from its conception to its end.
“Consider all impacts in context”		By including context, the impacts occurring in the product life cycle are evaluated as beneficial or potentially harmful.
“Assess to conditions of sustainability”	Environment	Comparing analysis with existing products’ solution is no longer required. The product is sustainable in its life cycle, or it is not.		*	*	**
	Social				**	**
	Economic				**	**
“Assess achievement”		A sustainable solution is assessed by achieving, rather than by reflecting progress improvement of existing solutions toward sustainability.

Table 1.

Evaluation of recent potential nature-inspired tools for impact assessment toward sustainability against the “achieving sustainability” paradigm.

^*

Provide a detailed way for calculation (quantitative).

^**

Qualitative.

The color indicates potentially promising.

Moreover, Terrier et al. [46], in 2019, proposed an assistance tool to provide a quantitative performance tool for biomimetic-based designs. This tool has been developed as a complement to the ISO 1845 standard. In this tool, the ten principles of biomimicry are grouped into three dimensions of biomimetics design: Efficiency and frugality, preservation and resilience, and circularity and systemic approach. Whether this tool is based on biomimicry or biomimetics, or the authors used these terms to refer to the same, needs to be clarified. However, this tool only assesses the environmental impact of the biomimetic design based on the midpoint approach in the LCIA, not including quantifications for other aspects of sustainability, that is, economy and society. Such a tool for impact assessment of biomimetic design still follows the “reduced unsustainability” paradigm due to the questions and metrics employed [46].

Furthermore, Peralta et al. [15], in 2021, proposed an upgrade to the cradle-to-cradle approach (a form of biomimicry) for sustainable designs. Since for the cradle-to-cradle approach there are not yet reported normative and guidelines, considering only environmental and social aspects qualitatively without any available tool, the proposed upgrade intends to assess both positive and negative impacts by dividing the assessment into three levels, that is, evaluating the LCI at micro, meso, and macro levels. At the micro level, the calculations are based on midpoint indicators; thus, they do not account for the entire context. At the meso level, the quality of the resources (or inputs) is evaluated. Finally, at the macro level, future effects are considered, including calculations for optimal design, allowing more sustainable product versions. The latter indicates that this proposed upgrade (or methodology) finalizes with assessing the product’s progress, which coincides with the “reduction of unsustainability” paradigm. Despite this, this proposed methodology advances the field by providing a quantitative tool for complementing the cradle-to-cradle approach [15].

Finally, later in the same year, among the interest in considering sustainability, a different approach based on biomimicry may have potential application toward the “achieving sustainability” paradigm. This approach, referred to as the “Biocircular model” by Beermann and Austin [40], is a conceptual nature-inspired approach built upon the sustainability consideration discrepancies among sustainable construction projects. Following the problem-based approach [47, 48], this Biocircular model is founded upon various biomimicry principles, combined with the circular economy and sustainability, leading to four supporting qualitative valuations, that is, active (A), behavior (B), housing (H), and share (S), that helps include sustainability as a target to the problem considered. Here, a complete qualitative analysis is presented for the six phases of construction projects, ending with the delivery phase, which was then supported by surveying experts in the field. Thus, as a qualitative approach that looks for the sustainability target in each phase of the construction projects individually, it coincides with the new paradigm previously mentioned. However, no quantitative criteria are provided [40]. Besides, existing indicators were contrasted with the Biocircular model approach, and none fulfilled the four supporting valuations. In contrast, four existing qualitative indicators did fulfill the supporting valuations: Reuse of construction elements [49], reuse of excavation materials for backfill [49], use of local material to reduce emissions [49], and water reuse system [50]. In a sense, this also follows the cradle-to-cradle principles.

3.2 Biomimicry, circularity, and sustainability in buildings

Now, a brief look into the applications of the arguments previously presented from the point of view of the built environment, specifically to sustainable construction projects such as net-zero-energy (NZE) buildings or green buildings.

Although the BiomiMETRIC tool [46] has an environmental dimension, in conjunction with the principles of sustainable construction [41], principles applicable to the LCA stages of a building were identified and can be visualized in Figure 6. While it is true that achieving sustainability requires going beyond the environmental impact, it is notorious that LCA can maximize its scope and approach, where the use of a second life through circularity in materials and components can have great benefits [39]. In the principles for biomimetic design, circularity is complemented by systematization, and beyond environmental preservation, resilience is addressed [46], which is a more developed degree of adaptation.

Figure 6.

Principles of sustainable buildings and biomimetic design applicable to the life cycle of a building.

Another approach not included in the sustainable principles but found in the Green Building Rating Systems (GBRT) [42] is efficiency and optimization, one of the most highlighted points when applying a biomimetic methodology to solve a problem. It should be emphasized that another challenge within the principles and their application is to maintain consistency between the different phases. In GBRT, the environmental dimension predominates with the number of indicators, while the construction and end-of-life phases have the fewest indicators [42].

In Table 2, matching principles were identified between [46] and [41] in order to obtain pinnacles, that is, biological entities that attend or act according to the established principles, applying the biomimetic methodology of “Living envelope” [51] complemented by the AskNature tool [52] from the Biomimicry Institute.

Area	Principle	Pinnacles
Efficiency and frugality	Reduce resource consumption	Bees
	Efficiency of materials and water/energy consumption	Eastern oyster/plants
	Source or buy local	Sacworm
Preservation and resilience	Protect nature	Earthworm
	Eliminate toxics	American Beaver
Circularity and Systemic approach	Reuse	Birds
	Recycle	Protoplasm of a protozoan
Design and Management	Quality	Bird (zebra finch)
	Diversify and cooperate	Meerkats

Table 2.

Pinnacles identified that meet the principles of biomimetics and sustainable construction according to area.

Based on the pinnacles found by [40], the inspirational capabilities in nature are illustrated:

• In the case of efficiency, there are several options for inspiration, such as bees, who forge their hives with the principle of storing the greatest amount of honey with the least amount of construction material, wax. While the oriental oyster already has a case of biomimicry by creating a type of calcium carbonate cement with softer and stickier features, which allows greater resistance to tides. In the use of the local, the sack worm utilizes materials around it, such as twigs and leaves, to build protection boxes.

• In environmental protection, beavers are examples of ecosystem engineers that shape entire landscapes, and earthworms add air and nutrients to the soil. By consuming organic matter, they decompose it to make it less harmful and excrete nutrients. Others, such as a protozoan, which feeds and creates its building elements, and birds, who always use materials at their disposal, including decomposed wood for their nests. This process for birds is essential, as they are also an example of quality because of the relevance and complexity of their construction, materials, and speed since their ability to reproduce depends on it.

In addition to the principles mentioned in Figure 6, design and management principles, such as quality and cooperation, were added in Table 2 to broaden the areas of principles that do not apply to the life cycle itself but are present in its formulation, strategy, and control, and which are increasingly becoming a necessity in early design [53]. Other principles regarding decentralization, such as diversity, redundancy, and independence, were not considered, as they can be included at the qualitative level of planning and management [54].

4. Discussion

The discussion of this chapter must start by framing the research questions presented at the beginning. Does the conventional LCA method need revision to change the paradigm? (i.e., achieving sustainability). The LCA method has been a research topic dating back to around 1997. As presented in previous sections, many variants and improvements to the LCA four phases can be found. Thus, rather than a revision of the entire method is well-established, a broadening of its LCIA boundaries [4] and interpretation phase is needed. The former helps the designers to think beyond the “this product solves this specific problem and is better than the others” toward “this product is beneficial because it solves this specific problem, and no collateral impact is created at present nor in future scenarios.” Here, the context is crucial [4], and thus, instead of letting the designer choose the impact assessment boundaries through its life cycle, it could reflect an advancement to the current variants of LCA.

However, encountered impact assessment tools still struggle to assess the achievement of sustainability of the product but assure advancement in the LCIA current indicators. Although the other two tools [15, 46] provide a quantitative framework for the LCIA, the Biocircular model [40] does not solely focus on providing a way of measuring sustainability but rather on working as a complement to the problem analyzed. This potential could be convenient to how LCIA is performed and interpreted in years to come, but the approach is in its early stages.

Hence, this brings us to our next research question. Could the biomimicry philosophy help improve the current LCA method? By highlighting the fundamentals and potential of the approaches encountered (Section 3), all three are based on biomimicry principles, including the cradle-to-cradle approach, which has its basis in a regenerative stage [7].

To demonstrate the application of the achieving sustainability assessment paradigm to the built environment, for instance, consider a net zero energy (NZE) design target for a new building and an existing building retrofitted toward the net zero target. Table 3 provides an approach to assess both building designs following the current LCA and the new paradigm. This is done only for the usage phase among the building life cycle but considers all three aspects of sustainability.

Design alternatives	Aspects to assess during usage phase	Sustainability aspects	Constituents for assessing the design alternatives
			Assessing progress; (as compared with existing no NZEB buildings)	Assessing achievement; (under the “if it would be” and binary orientation of sustainability [55])
New NZE building*	Electricity consumption	Environmental	80% of electricity consumption reduction as compared with existing no NZEB buildings.	Electricity consumption constraints are met to the limit they can be supplied by renewable sources.
	Electricity generation		20% of electricity generation comes from renewable sources.	Energy autonomy is achieved. Function 100% on renewable energy generated on site.
	Thermal comfort and IAQ	Social; welfare	Thermal discomfort is reduced and IAQ is improved.	100% of occupants’ indoor safety air quality is achieved.
	Costs**	Economical	Resources used can be provided by markets. Predictive maintenance	Predictive maintenance is automated. Systems lives are longer.
Retrofitted NZE building*	Electricity consumption	Environmental	70–90% of electricity consumption reduction via improvements in HVAC systems and envelope.	100% of electricity consumption are supplied by renewable sources.
	Electricity generation		10–30% of electricity generated comes from renewable sources on site	Energy autonomy is achieved. Function 100% on renewable energy generated on site.
	Thermal comfort and IAQ	Social; welfare	90% harmful pathogens reduction.	Pathogens levels are continuously monitored to avoid risks.
	Costs**	Economical	A 10% reduction of resources used from other no-local markets. Maintenance (corrective and predictive) plans are improved.	Resources used are only provided by markets. Systems lives are longer.

Table 3.

Differences in the assessment outcomes of two building design alternatives when using different constituents for the assessment (using [4] as reference for other case studies).

^*

Systems with normal levels of automation.

^**

Costs are related to resources and maintenance.

Other examples can be also assessed, for instance, positive energy buildings. In this case, the surplus is exported to provide and share with nearby buildings. Another example is sustainable construction projects. Table 4 presents an example of the binary orientation applied to the sustainable construction project under the “achieving sustainability” paradigm, taking as a reference the work of [40].

Design	Aspects to assess during usage phase	Sustainability aspects	Constituents for assessing the design alternatives
			Assessing progress; (as compared with existing no sustainable construction projects)	Assessing achievement; (under the “if it would be” and binary orientation of sustainability [55])
Sustainable construction project	Waste production	Environmental	20% waste production reduced.	Construction waste was recycled and reused in other projects as a resource.
	Life quality	Social; welfare	The life-lost rate is reduced to 1%.	No lives lost.
	Economic contribution	Economical	The unemployment rate was reduced by 10%.	The employment rate increased by 10%.

Table 4.

Differences in the assessment outcomes of a sustainable construction design project when using different constituents for the assessment (taking [40] as reference).

Moreover, a significant amount of quantitative and qualitative impact assessment indicators for sustainable construction projects are found in the literature. Such indicators can also be applicable to the impact assessment of other products or processes. However, it was noticed by [40] that none of the quantitative indicators have any limitations or threshold to offer a limit value that needs to be reached or passed in order to be considered as sustainable. Thinking about such limit value falls into the relative orientation of sustainability proposed by [55].

5. Conclusions

This chapter reviews the life cycle assessment method, its stages, and methods for impact assessment. Many LCA variants have been proposed to include other aspects of sustainability, that is, social (SLCA) and economic (life cycle costs), rather than only accounting for environmental impacts. Although many improvements have been proposed to the original LCA method version, the flexibility associated with framing the LCA boundaries according to the designer’s willingness stands out to assess the product’s impacts over its life cycle. This flexibility makes it difficult to push new design paradigms to achieve true sustainability in context. The biomimetic design approach follows such a design paradigm since it looks for natural inspiration but limits its focus to solving human problems.

On the other hand, biomimicry design approaches go further toward strictly achieving sustainability under the binary orientation. This before led us to ask whether biomimicry can help improve the current LCA method’s way of evaluating impacts, following the “nature success” philosophy. The literature analysis suggests that most impact assessment tools today still struggle to evaluate from the point of view of “achieving sustainability” instead of “reducing unsustainability.” Among the tools found, three potential tools based on biomimicry principles are analyzed. Only two provide detailed quantitative criteria but only for the environmental aspect and following the constituents of “assess to conditions of sustainability.” However, although these two tools greatly advance the current frameworks to evaluate impacts for biomimetic-based and cradle-to-cradle-based designs, they still present limitations on “assessing achievement” since their criteria reflects the assessment of progress improvement. Conversely, the Biocircular model approach offers great potential to frame the “achieving sustainability” paradigm since it still is in the early stages of development.

Moreover, two case studies were analyzed under the constituents of “achieving sustainability” and “assessing progress”: (i) a net zero energy building by comparing a new design with a design to retrofit, and (ii) a sustainable construction project. Both cases are analyzed under the usage phase of the life cycle.

Finally, the present work, by presenting the analysis of current LCIA tools from the point of view of the “achieving sustainability” paradigm, hopes to bring the attention of designers and engineers, especially to the construction sector. Urgency is required due to a rapid shortage of resources and a deliberate (or unintentional) increase in waste production.

Acknowledgments

The authors would like to thank the Technological University of Panama and the Faculty of Mechanical Engineering (https://fim.utp.ac.pa/, accessed on 18 January 2023) for their collaboration, together with the Research Group ECEB (https://eceb.utp.ac.pa/, accessed on 18 January 2023). The authors would also like to acknowledge the Chevening Scholarship program along the Geography Department at Birkbeck, University of London. This research was funded by a Panamanian Institution Secretaría Nacional de Ciencia, Tecnología e Innovación (SENACYT) https://www.senacyt.gob.pa/ (accessed on 18 January 2023), together with the Sistema Nacional de Investigación (SNI) SNI30-2021.

Conflict of interest

The authors declare no conflict of interest.