**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

### *Including Nature-Based Success Measurement Criteria in the Life Cycle Assessment DOI: http://dx.doi.org/10.5772/intechopen.110401*

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:


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.
