Global CO 2 capture and storage methods and a new approach to reduce the emissions of geothermal power plants with high CO 2 emissions: A case study from Turkey

Abstract

CO 2 gas is a main cause of the greenhouse effect, with atmospheric concentrations reaching 405 ppm in 2018. The main sources of CO 2 around the world are electricity production, heating, industrial purposes, and transportation. One of the critical factors, global energy-related CO 2 emissions, increased to 32.5 Gt in 2017. However, carbon capture technologies have improved and carbon storage methods are beginning to be used widely around the world. One option to minimize the effects of CO 2 gas is converting it into another product. In addition to carbon emissions due to hydrocarbons, geothermal power plants, which have the highest capacity among renewables sources, emit non-condensable gases such as CO 2 and H 2 S at high concentrations, based on geothermal reservoir characteristics and power cycle type. In Turkey, Italy, and some African countries that have important geothermal sources, geothermal-based CO 2 gas emissions are greater than elsewhere in the world. In Turkey, the country’s 40 installed geothermal power plants produce energy by different power cycles, such as binary, single, and multi-flash systems. The total installed capacity was approximately 1200 MWe in 2018 and is expected to reach to 4000 MWe in 2030. The non-condensable gases emitted from these plants are composed of 95–98% CO 2 gas and are due to the reservoir rocks, such as marble and limestone from Paleozoic-aged Menderes metamorphic rocks. CO 2 emissions emitted by the geothermal power plants range from 900 to 1300 gr/kwh and are inevitable because of the use of open cycles in Western Anatolia in Turkey. Only a small amount of waste CO 2 emissions have been used to produce dry ice in the region. However, Turkey is one of the countries that is required to reduce emissions according to the Kyoto and Paris Climate Agreements. A global problem is the capture of CO 2 gas and its storage or conversion to another product, which has been studied by researchers for a long time. A solution may be biofuel production from geothermal-based CO 2 in countries with geothermal power plants that are high producers of CO 2 emissions, such as Turkey and Italy. In this study, a conceptual design of the Helioculture process is applied to geothermal power plants to produce biofuel by CO 2 . The Helioculture process is a new approach by which it is possible to produce biofuel or ethanol using a photo-biocatalytic process. The process uses solar energy and waste CO 2 to catalyze the direct-to product synthesis of renewable fuel. It is evaluated with applicable technology for high-CO 2 producing geothermal power plants, such as the Kızıldere (Denizli) geothermal field in Turkey. Based on the results, Helioculture-based fuel production may be five times greater than traditional biodiesel production in the region. © Springer Nature Switzerland AG 2019.