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Researchers combine geothermal energy with CO2 capture to create a novel self-sustaining loop

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Researchers combine geothermal energy with CO2 capture to create a novel self-sustaining loop

In their strategy, CO2 pulled from the air is stored in deep, hot, saltwater aquifers; Heat brought to the surface is then used to power the DAC process.
February 22, 2024

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Renewable energy and low-carbon technologies are going to crucial for keeping the world’s temperatures from reaching dangerously high levels. Cost is often a hindrance, though. Finding synergy between technologies can sometimes help. Combining hydropower and solar is a good example, as is making sustainable fuel from food waste.

And now, researchers at Ohio State University propose combining carbon capture with clean, relatively cheap geothermal energy in a novel method that could make capturing carbon dioxide directly from more viable.

The system, reported in the journal Environmental Research Letters, recycles some of the captured carbon dioxide to transport geothermal energy in a closed loop that makes the overall direct air capture (DAC) process efficient.

Unlike carbon removal, which involves capturing carbon dioxide at the point of emissions, such as power plant or factory smokestacks, DAC technologies siphon carbon dioxide out of the atmosphere. The technology is starting to take off around the world, even though it remains controversial.

Twenty-seven DAC plants have been commissioned around the world until now, according to the International Energy Agency. And at least 130 facilities are at various planning and development stages. Most of these plants use giant fans to blow air over special chemicals that soak up carbon dioxide. But the methods can be expensive and require energy to operate.

 

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Martina Leveni and Jeffrey Bielicki set out to investigate whether carbon capture and geothermal energy technologies could benefit each other. In their strategy, carbon dioxide captured from air would be stored in deep underground geologic formations containing rock and saltwater.

The natural heat in these deep saline aquifers heats up the carbon dioxide, part of which is brought up to the surface. The heat could be used directly, or be converted into electricity, to power the DAC process.

For such a system to work in a self-sustaining way without needing external energy, the geothermal heat extraction system could first need some priming, the researchers say. That means about five years of storing carbon captured from concentrated sources such as smokestacks. After that, the facility would be able to produce enough renewable energy to start extracting the greenhouse gas from the air.

As a demonstration, the duo presented a case study of a potential system deployed in the Gulf Coast of the United States. Assuming their system could be operational by 2025, the system could start removing carbon by 2030. The researchers estimate that up to 25 hybrid geothermal–DAC systems could be set up in just one of the 27 geologic formations in the Gulf Coast by 2050.

“New technologies can enable one another, and in integrating them, we can tackle climate change,” said Leveni in a press release. “There’s a lot of work to be done to take into account technological readiness and the policies needed to make that research happen.”

Source: Martina Leveni and Jeffrey M Bielicki. A potential for climate benign direct air CO2 capture with CO2-driven geothermal utilization and storage (DACCUS), Environmental Research Letters, 2023.

Image by Herbert Bieser from Pixabay

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