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Geothermal CO 2Geothermal systems are located in areasexhibiting high CO 2fluxes inherent tothe geology of geothermal host structures.In volcanic environments much higherCO 2fluxes are the rule.Natural generationof CO 2in geothermalsystemsFor instance, in Italy, in the Central West Tyrrhenianregion, large amounts of CO 2are producedat depth as a consequence of marine carbonaterock metamorphism. During their ascent, gasesget trapped in deep seated structures includingpermeable mesozoic limestones overlain byimpervious capping terrains, which becomesources of high CO 2upward flows. For thisreason, deep ground waters are enriched indissolved CO 2. Metamorphic processes affectingcarbonate phyllites can also contribute toCO 2production from shallow crustal levels atca 8 km depths and 400-500°C temperatures,higher than those (3-4 km; 200-300°C) of theoverlying geothermal reservoir.LarderelloNoteworthy is that natural CO 2production is independentfrom geothermal exploitation. Actually,surface manifestations, characterised by hotwater and steam discharges from springs andfractures, can create an environment hostile tohuman settlements (Larderello, Yellowstone).Thanks to industrial geothermal exploitation,deep, eventually toxic, geothermal fluids could bechannelled, via geothermal wells and collectinglines, to power plants concentrating on a singlepoint (the plant chimney) natural emissions, whichwould otherwise contaminate the surrounding soilsand atmosphere over much larger areas.Summing up, geothermal CO 2emissions arenot generated by the industrial exploitationprocess.CO 2emission in electricity productionGeothermal,natural emission122Natural Gas315Oil760Coal9150 100 200 300 400 500 600 700 800 900 1000CO 2emission g/kWh8 EGEC | Geothermal Electricity and Combined Heat & Power
First experimentto producegeothermalpower, donein Italy in 1904by princeGinori ContiGeothermal electricity historyIn the early 1900’s, geothermal fluids werealready exploited for their energy content. Achemical industry was set up in Italy duringthat period, in the area known now as Larderello,to extract boric acid from natural hot water outletsor from purposely drilled shallow boreholes. Fromyears 1910 to 1940 the low pressure steam,in that area of Central Tuscany, was utilisedto heat industrial and residential buildings andgreenhouses. In 1928, Iceland, another pioneerin the utilisation of geothermal energy, beganexploiting its abundant geothermal resources(mainly hot waters) for domestic heating.This application, exemplified by Italy, was followedby several countries. In Japan, the first geothermalwells were drilled in 1919 and, in 1929, at TheGeysers, California, in the USA. In 1958, a smallgeothermal power plant started operating in NewZealand, in 1959 in Mexico, in 1960 in the USA,and in many other countries the following years.The first attempt to generate electricity from geothermalsteam dates back to 1904 at Larderello.The success of this experiment (see illustration)proved the industrial value of geothermal energyand marked the beginning of an exploitation routethat was developed significantly since then. Actually,electricity generation at Larderello was acommercial success. By 1942 the installed geothermoelectriccapacity had reached 128 MWe.GeothermalBook - Italy.PanoramaLarderello -TodayEGEC | Geothermal Electricity and Combined Heat & Power 9
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