## 6 Discussion
### CO\({}_{2}\) Emissions from GPPs  
The effect of geothermal power production on natural surface manifestations is still little known. [PERSON] and [PERSON] [52] have shown that geothermal power production led to a decrease in surface CO\({}_{2}\) natural manifestations in the Larderello geothermal field (Italy). [PERSON] et al. [15] suggested that surface manifestations in the Mt. Amiata geothermal field could have also decreased because of geothermal energy exploitation; however, predevelopment CO\({}_{2}\) emissions in the Mt. Amiata region are not available. [PERSON] and [PERSON] [52] suggested that if the reduced natural manifestations are countable, they should be subtracted from the GPP emissions. In some other foreign geothermal fields, however, CO\({}_{2}\) surface emissions have increased in response to the exploitation and to the reduced reservoir pressure, e.g., as observed in the Reykjanes geothermal field in Iceland [53; 54]. It is important to notice that AVGA and Iceland are characterized by very different geological contexts. Observation data relative to the Icelandic soil CO\({}_{2}\) flux are furthermore not areal normalized, which makes comparing the greenfield and brownfield areas more difficult. Figure 7: **(a)** sGs map of soil CO\({}_{2}\) flux AVGA superimposed on a 3D DTM (Digital Terrain Model) of AVGA; **(b)** Soil CO\({}_{2}\) flux profiles in relation to topographic profiles and geological sections reporting the main geological formations and the K-horizon, proxy of the granite intrusion. In the Mt. Amiata region, six GPPs are distributed between the Bagnore and Piancastagnaio geothermal fields, with a total installed capacity of 121 MW (Table 3). Three GPPs, two single flash units, and a binary group (ORC, Organic Rankine Cycle) are located in the Bagnore geothermal field, while three single flash units are located in the Piancastagnaio geothermal field (Figure 1). The annual electricity production in the Mt. Amiata region in 2018 was 1070.8 GWh [55], which represented 18% of the total geothermal electricity production in Italy (6105 GWh) [56]. The CO\({}_{2}\) emissions data from Italian GPPs are published annually by the Tuscany Regional Agency for Environmental Protection [13; 57; 58]. CO\({}_{2}\) represents the most abundant noncondensable gas emitted from Mt. Amiata GPPs, corresponding to 95.6% of the gas phase [28]. In addition, CO, H\({}_{2}\)S, NH\({}_{3}\), CH\({}_{4}\), Hg, As, Sb, N\({}_{2}\), He, Ar, and Se constitute the gas phase of the geothermal fluids in the Mt. Amiata reservoir [13; 15; 28]. Table 4 shows the CO\({}_{2}\) emission values from the single flash power plants in the Mt. Amiata area. In 2018, a CO\({}_{2}\) emission factor of 484 g/kWh was calculated as an average of all Mt. Amiata GPPs, while the emission factor computed for 2016 was 524 g/kWh (Piancastagnaio 5 data are missing) and for 2014 was 503 g/kWh (Bagnore 4 data are not considered). Bravi and Basosi [59] reported a weighted averaged emission rate of 497 g/kWh from 2002 to 2009. The total CO\({}_{2}\) emissions from GPPs in the Mt. Amiata area were 515,193 tons in 2018. The emission factors from GPPs around the world are shown in Table 5 for comparison. The CO\({}_{2}\) emissions from GPPs in the Mt. Amiata area are rather high if compared to the global world weighted average of 122 g/kWh [52] and the emissions of other GPPs around the world (except for Turkey and Larderello, Italy), but they are still small compared to emissions from traditional thermal power plants (Table 6). The CO\({}_{2}\) emissions for electricity generation from fossil-fueled power plants in Italy from 2017 [62] are reported in Table 6. Fossil-fueled power plants accounted for 70.5% of the total annual electricity generation in 2017. Table 7 shows that CO\({}_{2}\) emissions from Mt. Amiata GPPs are lower than thermal fossil-fueled power plants, except for natural gas power plants. The emissions from coal power plants are about two times greater than that of GPPs and the derived gas emissions are three times greater.