Arpat, in the last year without irregularities 100% of geothermal plants controlled

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Here is the focus published by the Regional Agency for Environmental Protection of Tuscany in the Yearbook 2022

After the advances already released in October, the Regional Agency for Environmental Protection of Tuscany (Arpat) has published the full version of the Yearbook 2022 – including a focus on geothermal power plants in the territory–, with which the Agency offers a detailed picture and updated to 2021 on the state of health of the Tuscan environment.

“Historically-argues the Director general of Arpat, Pietro Rubellini-the Yearbook has been elaborated considering the direct anthropic pressures as main impact factors through “sensu latu pollutions”, altering the pre-existing quality of the environment. By now the quality of environmental sectors is also considerably influenced by indirect pressures related to climate change, which unfortunately amplify current or chronic polluting impacts, altering natural and environmental resources, in quantitative and qualitative terms. The climatic stability and above all the seasonality of the weather has failed, affecting, for example, the ability of the water resource to regenerate with the rains, in a constant way and with the usual seasonality”.

From this point of view, the cultivation of geothermal resources to produce renewable energy represents a valuable protection tool, as geothermal energy does not add CO2 to the atmosphere compared to that released by the natural degassing of soils, and is indeed recognized by the IPCC as a useful tool to combat the climate crisis; it is no coincidence that the only large area of Europe certified with net zero emissions is that of the Province of Siena, where geothermal energy plays a leading role.

This does not mean that geothermal power plants, like any human activity, do not have zero impact: it is therefore necessary to monitor them in a timely manner, in order to verify that their activity is sustainable over time.

This is primarily dealt with by a public authority and super partes like the Arpat: as explained directly by the Agency, the Arpat “carries out the control of emissions into the atmosphere of the power plants and verifies the efficiency of abatement of mercury and hydrogen sulfide by the Amis treatment plant and, for the Bagnore plants, the efficiency of the system of abatement of ammonia and hydrogen sulfide in central entry”.

In 2021, out of “a total of 36 production groups present, 19 emission controls were carried out on 18 different plants”, with the result that “the emission values determined were all lower than the emission limit value”. In other words,” there were no exceedances of the emission limit values for the authorized parameters (mercury, hydrogen sulfide and sulfur dioxide)”, and therefore 100% of the controlled plants were found to be without irregularities.

In more detail, the Arpat explains that “there were no anomalies with respect to the emission limit values” of hydrogen sulfide released by geothermal power plants, which constitutes the substance with the characteristic smell of “rotten eggs”: “This olfactory perception occurs when the concentration in the air of this substance exceeds 7g power plants are equipped with a system of abatement of mercury and hydrogen sulfide present in the incondensable gases, called Amis, able to break down up to 99% of the hydrogen sulfide that is broken down in the gas leaving the condenser. The remaining part of hydrogen sulfide is broken down, instead of gas, in condensates, and a portion of it is emitted in the aeriform state by the cooling towers causing, sometimes, the threshold of olfactory perception to be exceeded”.

Looking instead at mercury emissions, even in this case “there were no anomalies with respect to the limit values”. On the merits, the Agency adds that “in Monte Amiata there is a significant geochemical anomaly due to the presence of mercury, therefore the population is exposed both for the natural component and for the emissive component of the power plants. The determinations of the exposure levels allowed to verify values very far from the limit value of health caution established by the international guidelines(Epa

Finally, with regard to sulfur dioxide, also in this case “there were no anomalies with respect to the emission limit values”. SO2 (also known as sulfur dioxide) is a colorless and irritating gas, the main responsible for the formation of acid rain.

“The formation of SO2 – they argue from the Agency – is a consequence of the abatement of hydrogen sulfide (H2S), as a result of its catalytic oxidation, inside the Amis plant. To prevent SO2 from being emitted into the atmosphere, before leaving the abatement plant, it is passed into the ” C2 ” washing column. Here it contacts, in countercurrent, the condensate water maintained at basic pH conditions; in this way the SO2 is solubilized in the condensate that falls into the system circle. A mass flow of SO2 not exceeding 200 g/h is allowed for the gas coming out of the Amis abatement plant”.

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