POROUS MATERIALS FOR CO2 CAPTURE IN GEOTHERMAL SYSTEMS

Abstract

The manifestation of the effects of climate change has underlined the need to curb down the levels of carbon dioxide (CO2) emitted in the atmosphere. The shift towards renewable energy (RE) sources has significantly decreased global CO2 emissions. While a zero carbon emission for the energy sector is unrealistic considering a full life cycle assessment; geothermal energy, which remains a reliable RE, has the highest CO2 emission equivalent per kilowatt-hour (kWh) during operations, compared to the other RE sources. Thus, there is a continuing movement within the geothermal industry for decarbonization. Present carbon capture and storage (CCS) methods include injecting CO2 into a porous reservoir below an impermeable caprock whether as a supercritical fluid or dissolved in either freshwater or geothermal brine. While these technologies effectively decrease CO2 emissions, they are energy intensive, require additional infrastructure and specific geological conditions. Thus, there is a need to look for alternative methods to help the decarbonization of the energy sector. Porous materials are being studied as alternatives to selectively capture CO2 from flue gas emitted from traditional thermal energy power plants. Metal organic frameworks (MOFs) and covalent organic frameworks (COFs) belong to this class of materials that use their high porosity and surface area to capture CO2 either by chemisorption or physisorption. MOFs and COFs can also be designed not only to store CO2 but convert it into other useful compounds. It is therefore proposed to explore the use of MOFs and COFs to capture CO2 in geothermal systems.