# Life-Cycle Assessment of Biofortified Productions: The Case of Selenium Potato
## 2 Materials and Methods
### Selenium Potato Life-Cycle Assessment
It was identified as 1 ha of cultivated surface because the objective of the work was to study the cultivation process with its environmental impacts; therefore, the marketable production was of secondary importance. As such, the FU was not identified in 1 kg of product obtained. Important within the first step was also the definition of the system boundaries (Figure 4); the choice fell on a \"from cradle to farm gate\" analysis, as a consequence of the reasons listed for the functional unit and the lack of data concerning the phases after harvest. The second step of an LCA is called inventory analysis; life cycle inventory (LCI) analysis consists of all details about all the environmental inputs (material and energy) and outputs (air, water, and soil emissions) at each stage of the life cycle [37]. Primary data from field surveys carried out with the help of the farmer and secondary data were used for the analysis. The latter refer to fertilizer and fuel production processes. These data were obtained from the Ecoinvent V 3.6 database [38]; in addition, both primary and secondary data were referred to the functional unit. The Ecoinvent database facilitates the application of LCA through the availability of a generic consistent background LCI data system; in fact, the lack of these can have a strong impact on the quality of LCA  
Figure 4: System boundaries in the LCA of selenium potatoes. Figure 3: Life-cycle assessment (LCA) of selenium potato. studies [39]. The environmental burden generated by the use of machinery and fertilizers was assessed according to Nemecek and Kagi [40]. Concerning the calculation of emissions due to the use of pesticides, the Ecoinvent approach was used, in which the amount of pesticides applied to the crop was considered as emissions to the soil. The substances in the inventories were used as references to correlate the corresponding emissions [40]. The third step is represented by the impact analysis, consisting of \"quantifying potential environmental impacts, through the selection of impact categories and, for all of them, relevant indicators and characterization models\" [35]. Life-cycle impact assessment (LCIA) helps the interpretation of LCA studies by translating these emissions into environmental impact scores [41]. Characterization factors at the midpoint level are located somewhere along the impact pathway, typically at the point after which the environmental mechanism is identical for all environmental flows assigned to that impact category [34]. The impact categories considered for the evaluation were global warming (GW), stratospheric ozone depletion (SOD), ionizing radiation (IR), ozone formation, human health (OFH), fine particulate matter formation (FP), ozone formation, terrestrial ecosystems (OFT), terrestrial acidification (TA), freshwater eutrophication (FE), marine eutrophication (ME), terrestrial ecotoxicity (TE), freshwater ecotoxicity (F), marine ecotoxicity (M), human carcinogenic toxicity (HCT), human noncarcinogenic toxicity (HNT), land use (LU), mineral resource scarcity (MS), fossil resource scarcity (FS), and water consumption (WC). In this study, a comparison was also made between the sustainability performance of the selenium potato compared to conventional potatoes in the same areas of study. The data concerning the latter refer to potato cultivation in the same reference area and were taken from an LCA study carried out by [PERSON] et al. [42]. Table 1 shows the measurement units of each impact category analyzed to facilitate their interpretation.