The boundaries of research and data collection are defined following a meticulous description of the system under study and the construction of the flow diagram of the production cycle. An initial delimitation of the boundaries will be carried out based on both geographical and technological criteria, including within the scope of research the physical environments and production processes that are deemed necessary for the analysis. Subsequently, as the study progresses, it will be possible to exclude components that prove to be irrelevant or for which obtaining detailed information would be too costly, or to include others to which adequate importance was not initially attributed. In other cases, it is a specific requirement of those commissioning the study to already exclude certain phases of the production cycle a priori. Typical analyses are "from cradle to gate" if the analysis is interrupted at the end of the production process, or "from cradle to grave of the product/service" if the interruption occurs when the product or service reaches the end of its useful life ready to be disposed of.
It is understood that the choice of the analysis boundary must be adequately motivated and always indicated in the drafting of the study. In conclusion, it can be stated that every LCA study contains simplifications and limitations to make it manageable compared to a complete LCA of the global industrial system, which for obvious reasons will practically never be fully replicable. The objective of an LCA is to trace back all the production chains of the investigated system to the extraction of raw materials in the most complete form possible and evaluate the error made by neglecting particular process units. ISO 14040 is very clear on this point: "the criteria adopted in establishing the system boundaries must be identified and justified in the study's scope of application".
The reference period (temporal boundaries) also constitutes a constraint in the choice of analysis boundaries: data must be collected within a well-defined period of time. They can also represent an average system operating condition, or the best available technology (BAT, Best Available Technology). The environmental impacts, analyzed in the Impact Assessment phase, are characterized by a sphere of influence (global, regional, or local) and the characterization parameters are time-dependent (the temporal horizon of the greenhouse effect can be 20, 50, 100, 200, or 500 years).
All this information (III a, III b, and III c) constitutes the foundation of any LCA study and is grouped together, according to UNI EN ISO 14040, in the so-called "scope of the study", which therefore represents a kind of business card with the study's requirements, limitations, assumptions, and initial hypotheses with which the technician intends to address the study.
