Relationship between CO2 and geothermal energy in Tuscany


Enel Green Power’s Sasso 2 geothermal power station, Tuscany, Italy (source: Volcanex)

It is crucial to trust science and research and not incorrect information that has slowed down the development of geothermal energy as a valuable energy resource for Italy, a new study has therefore published.

Three new studies, published by Italian researchers – with a leading role from the University of Pisa – in prestigious international journals are finally helping to shed light on a subject that has been controversial for too long: what relationship is there between the industrial culture of geothermal energy and CO2 emissions into the atmosphere? This question is addressed in a recent Greenreport article earlier this month. This renewable source has always been naturally present in Tuscany, the first territory in the world that managed to tame it more than a century ago, achieving extraordinary results.

Today, more than 70% of the electricity we consume from renewable sources is guaranteed, in Tuscany, by geothermal energy: in other words, the heat of the earth covers a third of all our electricity needs and directly supplies energy. ‘significant amounts of heat.

Yet doubts have always remained about the climate-altering emissions associated with geothermal power plants. Pollutant emissions are regularly checked by the competent authorities (mainly ARPAT) certifying constant compliance with the regulations in force. But what about CO2? Do power plant discharges replace natural soil emissions or are they additional?

The new studies published after years of intense research directly in the field finally paint a precise picture, both for the region of Larderello and for the region of Amiata. We spoke about it directly with Alessandro Sbrana, professor in the Department of Earth Sciences at the University of Pisa and co-author of the research in question.

The use of geothermal energy for industrial purposes began for the first time in Tuscany: a world record that makes it difficult to assess the effects of geothermal generation on parameters such as CO2 emissions, given the lack of reliable data on the relative soil degassing. over two centuries ago. New study uses historical data on boric acid production as an indicator: How can we estimate past CO2 emissions?

“The authors of the work published in the journal Energies made it possible to estimate the CO2 emissions before the geothermal generation at Larderello, starting with the production of boric acid extracted in 1800 and at the beginning of the 20th century in the so-called “lagoons”, which gradually disappeared in the first years of the ‘900, when the condensation of geothermal vapors took place.

In the lagoons, the condensation of the vapor rich in boron, an element similar to the vapor phase, caused the precipitation of a solid phase of boric acid (H3BO3) in the condensation water of the lagoons which was then extracted; the quantities of ore extracted were recorded in the archives of the mining industry of the time. Data on the amount of boron extracted provided an estimate of the amount of steam that escaped from geothermal reservoirs during the period considered.

This is the starting point that was used for estimating CO2 emissions before the industrial development of geothermal energy. The measurement of the ratio between CO2 and water vapor, measured by Payen at Larderello in 1841, and the knowledge of the concentration of boron in the vapor made it possible to calculate the quantity of incondensable gas, the CO2 emitted during the period of extraction of boron in Boraciferous Lagoni of Larderello between 1818 and 1867 from tons of boric acid.

This estimate is the only and valuable indication of the amount of steam and gas that was released into the atmosphere prior to the cultivation of current geothermal fields. It is obviously limited to the area of ​​major natural manifestations of the Devil’s Valley, which have now almost disappeared, replaced by gaseous emissions and mineralized thermal aquifers in various places in the Valley.

The results of this research published in a special volume of Energies , a prestigious international multidisciplinary journal dedicated to energy, provides the first quantitative indication of the quantity of greenhouse gases (CO2) and vapor naturally released into the atmosphere.

It is estimated that in the Valle del Diavolo there was a natural steam emission for about 236 t / h with 17 t / h of CO2 associated, which in terms of geothermal power plant corresponds to a power plant of 130-140 MW. Today, the flow of steam and gas in the Devil’s Valley is extremely reduced under the effect of more than a century of geothermal generation, which is still cultivated while maintaining the reservoirs in equilibrium ”.

The article ends with an overview of the best technological solutions to date for cultivating geothermal fluids in an increasingly sustainable way, both in terms of electricity and heat production.

… And in the Italian context, the article underlines that “in the case of geothermal energy, we must trust science and research and offer the inhabitants of the region the results obtained which respond to the erroneous information that has unfortunately slowed down the development of this precious energy resource. … there is not much to add

For the full article, see the link below (in Italian).

Source: Green report

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