2.4.4. Economic Function

Economic viability is a crucial prerequisite for any technical system and is usually defined as feasibility in terms of a business model or economic product life cycle. While it is oftentimes not the ultimate purpose, economic viability is an essential means to function fulfilment, which is why the economic function is regarded as separate aspect.

Even though no direct analogy can be drawn between nonhuman biological systems and economic viability, its basic function offers some similarities between evolutionary fitness and economic success [7]. The behavior of companies is to some extent comparable to evolutionary mechanisms of selection and niche occupation, as indicated through analogies in terminology [70]. The two main areas of protection are derived from this analogy and are defined as profitability (efficiency) and competitiveness (fitness). While these aspects are addressed in detail in business practices, they are oftentimes not regarded within product development, especially in early development phases. Therefore, a basic system shown in Table 3 is proposed based on the framework presented above, combining PIC and FNI. On the basic level, the material and energy cost optimum is related to a potential market price based on existing competing products. These values are then complemented through further nonmaterial information on labor costs, investment goods and detailed information on the market situation including potential market prices as well as a potential product price and market volume estimation.


**Table 3.** Categories and weighting structure for the assessment of the economic function.

## 2.4.5. Social Burden

In contrast to economic and environmental aspects, the definition of social burdens cannot be derived from a state of the art assessment methodology. The main difference can be identified in the ambiguity of social impacts in terms of goal and scope and the fact that the physical quantification for most categories is not applicable due to its immaterial nature [71]. While for social life cycle assessment no method has prevailed yet, a guideline providing general recommendations was published by the United Nations Environment Programme [50,51,72]. Furthermore, Sureau et al. have investigated 14 different frameworks for social LCA and identified high diversity between the approaches as well as substantial demand for further development [49]. From an epistemological point of view, the underlying scientific paradigm is differing between post-positivism- and interpretivism-oriented approaches [73]. While interpretivism-based approaches are aggregating impacts that are mainly chosen case specific with regard to stakeholder groups, interpretivism-oriented approaches are developed in analogy to environmental LCA, trying to provide quantifiable, generally valid impact pathways to be applied to life cycle system models [74]. While the thereby developed methods differ in their approaches to choose and define indicators and assess its inherent impacts, their common denominator is the identification of effects of a system's life cycle with regard to social aspects based on explicitly or implicitly chosen frameworks.

Looking at nonhuman biological systems, ethics, morality and altruism are concepts that do not seem to be relevant in most biological (non-human) systems, even though exceptions are known [75,76]. Though still subject to scientific controversy, morality and altruism and the consequent concept of ethics may be an integral part of the evolutionary success of humanity and are therefore key to its understanding and its ongoing success [77,78]. The assessment of social burdens is therefore interpreted as the depletion of societal resources, which are defined as human health and human capabilities. These are the basic prerequisites for humans to live a self-determined life and for society to prosper [79]. Human health is assessed through the LCA model, applying the same distance to target normalization approach as for environmental burdens for the human health related impact categories (Table 4) [59]. Again, the proposed impact categories are replaced by updated version if available, which in the case of human health applies to the USETOX model [80]. The concept of human capabilities to address social impacts has been developed based on the capability approach as framed by Sen [79,81]. It is applied in a hybrid approach using the Social Hotspots Database (SHDB) for quantification of the impact categories based on risk levels, which are available on country and sector level [82]. The risks are linked with the product system using a bottom-up approach to assign working time to each unit process of the model based on statistical data according to an updated and extended version of the Life Cycle Working Environment (LCWE) method. The chosen method can be characterized as environmental LCI database method according to the differentiation provided by Chhipi-Shrestha et al. (2014) [73]. The model is integrated in the GaBi software and thus applicable using the enhanced LCI model, providing working time in seconds for both aggregated and unit processes. While the method is still under development, it has already successfully been applied in several research projects [83–85]. The indicators are each calculated as both total working seconds under high and very high risk of each category and its share related to the overall working time. The indicators have been chosen based on the framework introduced by Reitinger et al., 2011, which adds fairness to the categories introduced by Sen [79,86]. To prevent double counting, the aspect of health and safety is covered by the LCA impact assessment and not included in the capability assessment.


**Table 4.** Categories and weighting structure for the assessment of the social burden.

## 2.4.6. Social Function

The function of a technical system can ultimately be defined as to serve a specific, desired purpose. While these functions can be distinguished between design functions, use functions and service functions only design function can be considered for product development as this is the function that was designed as a means of achieving its end [42]. It is therefore a crucial aspect to be considered when designing or developing products to address the specific function or functions.

In biological systems, the concept of function is defined differently and mainly applied with regard to evolution and fitness [41,87]. Nevertheless, it is possible to investigate and quantify physical properties of biological systems with regard to their technical design function. Especially in biomimetic science, the identification of these functional principles is key to successfully transfer its core working principles to technical solutions [88]. To define these technical design functions with focus on the area of application of this model, the building physical functions specified by Moro are applied as design functions (see Table 5) [89]. As most products are only focusing on one or a few of these functions, the use of a generalizable quantification system for all categories was not applied. The presented impact categories and the according building physical functions shall be used as catalog to choose the design function including multifunctional properties, each of which then should be assessed individually based on the according building physical properties. When a product is developed as load bearing element, for instance, its design has to be chosen to bear not less load than the reference system and its dimensioning has to be chosen accordingly.


**Table 5.** Categories and weighting structure for the assessment of the social function, restricted to building physical functions [89].
