After nearly a decade of only small development in capacity in deep geothermal sector in Europe, in recent years a resurgence of interest in geothermal power and the use of innovative technologies to increase and better exploit geo-thermoelectric generation has stolen the limelight from the scientific community. Differently from other types of energy sources, the environmental impacts determined by geothermal exploitation are extremely dependent on the geographical location. Life Cycle Assessment offers a powerful methodological approach for the investigation of the environmental footprint of power generation systems. Focusing on an unprecedented system-modelling approach for the investigation of an environmental impacts analysis of geo-thermoelectric activity in the Tuscany Region, Italy, in this work we perform a comprehensive environmental impact assessment for the calculation of atmospheric emissions profiles connected with the operational phase of the power plants. A clustering of all the geothermal installations in operation nowadays is performed by considering geographical representativeness This allows the identification of regional geothermal subareas. Moreover, an extensive data processing analysis is implemented with the aim of reconciling the great variability found among data collected. Results demonstrate that the efforts undertaken by the operator of the geothermal power plants to limit the impact of emissions, through abatement systems like AMIS, are quite effective. Indeed, in areas where mercury and ammonia concentration in fluids constitute a problem to deal with, nowadays the emissive patterns result comparable to the other ones. Notwithstanding, mercury and ammonia emissions, mainly emitted through the cooling towers, still represent a critical problem for all the geothermal fields. On the basis of our findings we conclude that potential chemical interactions and environmental impacts related to the variety of the compounds emitted should be object of future research and a further effort to minimize them.

Introduction

Geothermal energy has been perceived as a convenient source for electric energy production only on a local scale so far, as just few areas in the world have enough geothermal potential to exploit it. Italy, Iceland, some U.S. States, Indonesia, Philippines, New Zealand are some of the countries that have already benefited from its exploitation. In recent years things have changed, and geothermal energy is now considered as one of the most promising renewable energy sources for producing electricity and heating. This is also proven by significant investments that are being made at international level: in fact, new technologies could allow the exploitation of reservoirs that would have been impossible to use in a costeffective way until now (very deep drilling, binary cycle for low temperature fields, Enhanced Geothermal System). So far, environmental concerns perceived by the community have been one of the important barriers especially for deep geothermal market development. In this context, nowadays decision-makers require more reliability in the environmental performance assessment of the power plants. In fact, differently from other types of energy sources, the environmental impacts determined by geothermal exploitation are extremely dependent on the geographical location. Concerning the global panorama of the geo-thermoelectric market, traditional hydrothermal flash power plants still dominate in terms of installed capacity all over the world, because of the greater electrical production that such technology can generate compared to others. In fact, according to the World Geothermal Congress survey, in 2015 only 1.8 GWe of the total 12.6 GWe world installed capacity was represented by binary power plants, while innovative enhanced geothermal technologies (EGS) were just not representative. Moreover, concerning the produced electrical geothermal energy in that year, only 12% was obtained from binary power plants. (Bertani, 2016).