*2.2. LCA Methodological Approach*

## 2.2.1. Goal and Functional Unit

The goal of the present LCA study is to assess the potential environmental impacts that are associated with the production of electricity from the geothermal power plants of Bagnore 3 and Bagnore 4. The functional unit selected is 1 kWh of net electricity produced. This study was conducted according to the requirements of ISO 14040 standard series [39,40] and the ILCD Handbook [41], following an attributional approach. The broader scope of the study was to provide insight and reference values on the environmental performances of an operating flash-based geothermal facility relying on a very detailed LCI. The intended application was to calculate the comprehensive eco-profile of the Bagnore power plants system. Data for building the life cycle inventory was obtained directly from EGP through accurate surveys and questionnaires.

#### 2.2.2. System Boundaries

Figure 1 shows the system boundaries of the LCA study. The system modelling approach is cradle to grave, and it included the following phases: commissioning, operation and maintenance (which together constitute the use phase), decommissioning and end of life (EoL). The system boundaries were set up to the point where energy, in the form of electricity and heat, is produced from the plant. The distribution of energy was not considered. The life cycle phases included in the boundaries were modelled using foreground and background processes. The distinction between the foreground and background processes consists of the former being explicitly modelled for the investigated system employing data directly measured in situ, and is therefore highly representative of the technological and geographical situation of the studied system (primary data). Background processes are all the other processes for which data were retrieved from the Ecoinvent database version 3.5 [42] (secondary data). Background processes represent an average situation with a different level of geographical and technological representativeness, ranging from national to worldwide averages.

**Figure 1.** Graphical representation of the system boundaries considered in this study. A distinction is made between background processes that use secondary data (Ecoinvent database v3.5) and foreground processes that use primary data representative of the Bagnore power plant system. Electricity and heat distribution infrastructure and processes are not included in this study.

The geothermal power plant system was modelled in more detail, as follows:

(1) The commissioning phase included the drilling of production and injection wells and the well-pad construction; the construction of pipelines; the power plants building; all the equipment needed for the power generation plant and the heating station, including the cooling towers, the ORC unit and the production of the working fluid used by the ORC system; the construction of AMIS was also included in the commissioning stage; on the contrary, the exploration and wells' testing stages were excluded from the analysis, due to lack of data.

