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In many geothermal areas, an abatement of hydrochloric acid present in the steam is essential in order to produce energy before turbine expansion. In fact, concentrations of acid higher than 5 ppm risk seriously corroding the turbine, significantly increasing the costs of this energy source. In 2018, Enel Green Power decided to support a research project, called Georockwash, and aimed at identifying a new process for the abatement of HCl in geothermal steam with the collaboration of Magona Technological Pole, as a centre specialized in the experimentation of industrial processes on a pilot scale. The project has developed a new abatement process based on the use of dry CaCO3, as agent for the neutralization of acid. The process has been tested initially on a laboratory scale and then on a pilot scale with the construction of a 500 kg/h steam plant, skid mounted and transportable. The experimentation campaign on the pilot plant was conducted first at the facilities of the Magona Pole and then at an Enel Green Power geothermal power plant. In the experimentation the effects of the main operating parameters on the abatement efficiency were evaluated and correlated with a semi-empirical equation. Finally, the experimentation showed abatement efficiencies often higher than 95%, confirming the suitability of the new process for geothermal use with low investment and operating costs. [ABSTRACT FROM AUTHOR]

Geothermal energy is a key renewable energy for Italy, with an annual electric production of 6.18 TWh. The future of geothermal energy is concerned with clarity over the CO2 emissions from power plants and geological contexts where CO2 is produced naturally. The Mt. Amiata volcanic–geothermal area (AVGA) is a formidable natural laboratory for investigating the relative roles of natural degassing of CO2 and CO2 emissions from geothermal power plants (GPPs). This research is based on measuring the soil gas flux in the AVGA and comparing the diffuse volcanic soil gas emissions with the emissions from geothermal fields in operation. The natural flux of soil gas is high, independently from the occurrence of GPPs in the area, and the budget for natural diffuse gas flux is high with respect to power plant gas emissions. Furthermore, the CO2 emitted from power plants seems to reduce the amount of natural emissions because of the gas flow operated by power plants. During the GPPs' life cycle, CO2 emissions in the atmosphere are reduced further because of the reinjection of gas-free aqueous fluids in geothermal reservoirs. Therefore, the currently operating GPPs in the AVGA produce energy at a zero-emission level. [ABSTRACT FROM AUTHOR]

The impact of natural CO2 emissions in the development of geothermal areas is presently gaining more attention than ever before. In Italian geothermal fields, a reduction in the natural CO2 emissions has been observed. This paper reviews and provides an analysis of the historical production data of boric acid from 1818 to 1867 used to calculate the natural emissions of CO2 associated with boric acid production that pre-dates the use of geothermal resources for power production, which started in 1913. Boric acid was already being extracted from the natural geothermal fluids in geysers and natural ponds emitting steam and gases. After 1827 the 'lagone coperto' (covered lake) equipment optimized production, and the drilling of shallow wells (20–30 m) starting in 1836, which further increased the quantity of its extraction. The first geothermal reservoir was developed at the turn of the century and the Larderello geothermal field began to grow. The use of deep wells, keeping pace with the power production, led to the gradual disappearance of the natural ponds and the 'lagoni' (lakes) in the historical area, so the residual natural emission of CO2 is presently restricted to diffuse soil emission. Comparisons of the ancient CO2 emissions with those of the Geothermal Power Plant (GPP) in the Larderello area show that both amounts are in the same order of magnitude, suggesting a balance between the depletion of natural emissions and geothermal activity. [ABSTRACT FROM AUTHOR]

Geothermal plants have been producing power in Italy for more than a century. Since local opposition to geothermal development is often fuelled by incomplete and inaccurate environmental information, this paper provides a comprehensive description of the effect of geothermal development on the air, water and soil and investigates potential disturbance from noise, subsidence, and seismicity, as well as the visual impact on the local area. After discussing the risks associated with the geothermal development and the reference data, the paper describes the wide-reaching environmental monitoring and mitigation measures in Italy that have maintained impact values below the thresholds defined by European and Italian regulation. The social benefits for areas where geothermal energy is developed are also described, with the aid of case studies highlighting that citizens do not feel that they are sufficiently informed to have a voice in the innovation process. A regular and comprehensive review of the geothermal environmental and safety regime, as the one carried out in this paper, and a mutual exchange of knowledge between the different stakeholders should be strongly encouraged. [ABSTRACT FROM AUTHOR]