Geochemical Characteristics of the Kızıldere Geothermal System (Turkey) and a Case Study for Emission Reduction in the Kızıldere Geothermal Field

The Kızıldere geothermal field, located in the eastern part of the Büyük Menderes Graben, is one of the most productive geothermal systems in Western Anatolia (Türkiye). Electricity production in the field, which began in 1984, is still ongoing with three flash type geothermal power plants.

Four geothermal reservoirs with different rock compositions and geochemical characteristics have been identified in Kızıldere geothermal system. Steam production has changed over time from a shallow reservoir to the hottest deep reservoirs in the system. In the steam phase, CO₂ is the dominant gas type in the Kızıldere geothermal system, with concentrations ranging from 98% to 99%. The ¹³C analyses revealed that the primary source of CO₂ is Paleozoic aged metamorphics and that the origin of CO₂ is primarily reservoir carbonate dissolution. The deep reservoir contains sulfate, sulfide minerals, dissolved sulfate, dissolved sulfide (HS-), H₂S gas, and organic sulfur compounds. Sulfate in thermal waters could be caused by gypsum dissolution or the oxidation of sulfides such as pyrite and pyrrhotite.

In this study, the possibilities of reducing H₂S and CO₂ emissions by chemical and biological methods were investigated, taking into account the characteristics of the Kızıldere geothermal system. For this purpose, field tests were carried out with 6 different solutions  and the selected bacteria to examine the reduction of non-condensable gases in the Kızıldere geothermal field.