A geothermal, climate-friendly way to capture carbon dioxide from the air

In a new study, researchers have developed a method for capturing carbon dioxide from the atmosphere, powered by clean and relatively inexpensive geothermal energy.

Their conclusions, published in the journal Environmental Research Lettersreveal that by combining direct air carbon dioxide capture (DACC) technologies and geothermal energy, carbon dioxide (CO₂) removal systems could potentially be powered with enough energy to remove carbon dioxide from the atmosphere and store it safely underground.

Emitted when humans burn fossil fuels for heat, electricity and transportation, carbon dioxide makes up the majority of greenhouse gases emitted by human activities into the atmosphere. As this accumulation is one of the main drivers of climate change, efforts to combat this excess have focused on methods of extracting carbon dioxide, either at the original emission source or directly from it. ‘air.

“Carbon removal technologies are particularly useful for mitigating climate change because we can capture types of emissions that would be difficult to limit by other means,” said Martina Leveni, lead author of the study and postdoctoral researcher in civil, environmental and geodetic engineering at the University of California. The Ohio State University. “So we thought: Could we combine technologies that could benefit each other to achieve this goal more effectively?”

Typical DACC methods can be expensive and require energy to operate, adding more greenhouse gases to the atmosphere, Leveni said. But she decided to study whether it was possible to integrate recycled carbon dioxide into the system to make it more efficient.

Called Direct Air CO₂ Capture with CO₂ Utilization and Storage (DACCUS), the method proposed by Leveni uses natural heat stored beneath the Earth’s surface in deep saline aquifers (underground geological formations containing sedimentary rocks and salt water) to continuously produce renewable energy for DACC systems.

Carbon dioxide captured from the air is isolated in these geological formations and some can be circulated to extract geothermal heat. This circulation brings heat to the surface, where it can be used directly or converted into electricity to power the system.

Such a system requires a lot of energy, which can often lead to more pollution. But it’s an issue their work takes into account, said Jeff Bielicki, study co-author and associate professor of civil, environmental and geodetic engineering at Ohio State’s John Glenn College of Public Affairs.

Geothermal energy generally has a very low carbon footprint, and this particular approach is even lower because it uses carbon dioxide, Bielicki said.

To demonstrate the potential of their system, the researchers developed a case study of how it could work in the U.S. Gulf Coast region. They determined that DACCUS could be deployed there with great success, as it is renowned for its vast geothermal resources.

“The Gulf Coast also has the right geology to safely store carbon dioxide underground and a decent enough heat flow that its geothermal energy can be used in sufficient quantities,” Bielicki said. “These characteristics are very favorable.”

For their system to work, the geothermal heat extraction system must first be primed, much like a car engine. It takes about five years of storing carbon from point sources, such as factories that emit carbon dioxide, before a DACCUS facility begins pulling greenhouse gases from the air.

Assuming their system can be operational by 2025, the study suggests its method could begin removing carbon by 2030. The researchers estimate there could be as many as 25 DACCUS systems installed in a single of the 27 geological formations on the Gulf Coast by 2050.

Nonetheless, this study offers hope for our climate future by highlighting the importance of merging new ideas and concepts to better achieve a distant goal, Leveni said. The study suggests that if implemented, this team’s work could even help society achieve its current goal of limiting Earth’s warming, while avoiding some of the worst consequences of climate change.

“New technologies can reinforce each other and, by integrating them, we can fight climate change,” Leveni said. “There is a lot of work to be done to consider the technological readiness and policies needed to carry out this research.”