Powering Carbon Capture With Geothermal Energy
Ohio State University researchers have developed a system combining direct air carbon capture technology with geothermal energy to remove carbon dioxide from the atmosphere while generating renewable power.
Removing carbon dioxide (CO2) from the atmosphere requires active measures and technological intervention. Direct air carbon capture (DACC) is one common approach to carbon removal.
To improve the scalability of DACC, Ohio State University researchers have developed a way to power DACC systems using a reliable ecological process: geothermal energy.
Carbon emissions. Image used courtesy of Pexels
Geothermal Carbon Capture
DACC involves the extraction of carbon dioxide directly from ambient air, regardless of its source, such as industrial processes or transportation. Unlike traditional carbon capture methods, which target emissions at their source, DACC has the advantage of capturing CO2 from dispersed sources, making it particularly attractive for reducing atmospheric carbon levels.
Unfortunately, DACC systems demand energy, often from fossil fuels. The process can create as much CO2 as the system purports to capture.
The Ohio State research team sought to address this problem. Their approach, Direct Air Carbon Capture with Carbon Utilization and Storage (DACCUS), combines a typical DACC system with geothermal power to reduce atmospheric carbon concentrations without generating more.
Geothermal energy is a naturally occurring process derived from the heat stored within the Earth, originating from radioactive materials that decay naturally in the Earth’s core. The energy is harnessed by tapping into hot water and steam reservoirs beneath the Earth's surface or utilizing the heat from shallow ground sources.
DACCUS captures CO2 from the atmosphere and securely deposits it deep underground within designated rock formations. This process effectively reduces greenhouse gas emissions and is proactive in combating climate change through carbon extraction.
Carbon Utilization for Renewable Energy
DACCUS is unique to carbon capture technologies because it utilizes the captured CO2 to enhance the effectiveness of geothermal energy extraction. The underground circulation of CO2 brings geothermal heat closer to the surface to improve the extraction rate of geothermal power plants without requiring more fossil fuels.
The Ohio State team has found an innovative solution to integrate mutually beneficial technologies supporting carbon reduction efforts.
DACCUS system configurations. Image used courtesy of IOPScience
The team chose the United States Gulf Coast to conduct a case study on the DACCUS system, given the region's abundance of CO2 point sources and favorable geothermal heat fluxes.
Using data from prior analyses, the study examines two DACCUS configurations. The first is a DACCUS heat system using geothermal heat to regenerate the solid sorbet in the DACC process. The second is a DACCUS heat and power system powered by the electricity generated from geothermal heat production.
They found deeper CO2 storage reservoirs (greater than 3.5 km) with higher geothermal temperature gradients (greater than 35°C for every 1 km) may yield adequate production wellhead temperatures (greater than 100°C) and meet the electric load requirements in 93 percent of the reservoir characteristic combinations scrutinized.
The case study anticipates up to 25 DACCUS systems will be operational within a single geological formation in the region by 2050. However, implementing these systems necessitates a five-year preparatory phase, during which carbon from diverse point sources such as factories will be stored. After these five years, the DACCUS facility can begin direct air carbon capture.
The opportunities for DACCUS are extensive following successful implementation with decreasing atmospheric CO2 levels and producing renewable energy. The advent of this system represents a notable advancement in carbon capture and storage technologies and showcases the benefit of interdisciplinary research.
