Is it possible to 'permanently' remove CO2 from the atmosphere? Science found a way

Carbon dioxide has long been a huge source of concern for people who want cleaner air, cooler water, and a healthier planet. Many nations are working to slash emissions of this gas, but experts say that may not be enough.

This is where strategies like sucking CO₂ from the air and stashing it deep under the Earth’s surface gain attention.

This approach is now being investigated by Marco De Paoli from the University of Twente (UT) in Enschede, Netherlands, and the Institute of Fluid Mechanics and Heat Transfer at TU Wien.

Why storing CO₂ underground is complex

CO₂ does not simply vanish once injected below the surface of the Earth. It occupies spaces in underground rocks and mixes with groundwater, a process that turns out to be more intricate than it first sounds.

Many scientists have wondered if it could creep back to the surface after decades.

“Pure CO₂ has a lower density than water, but the situation changes when CO₂ is dissolved in water,” stated De Paoli.

Numerical experiments on large computers suggest that once CO₂ dissolves in water, the resulting liquid is denser than water alone. 

Dense carbon water sinks and stays put

Density is crucial for how fluids behave underground. When carbon-rich water is heavier, it tends to move downward instead of floating back up towards the surface.

This internal sinking motion creates layers of fluid that stay tucked away underground.

Those denser layers mean storage can be more than a temporary band-aid.

Officials who track environmental tactics see this density-driven process as a real chance to keep CO₂ locked beneath rock layers. This would help minimize leaks that might compromise long-term climate goals.

Only some places can store carbon safely

Not every location is a fit for CO₂ storage. There must be a thick, relatively impermeable caprock above a porous layer that holds groundwater.

A secure lid is vital to keep CO₂ in place until it fully dissolves and starts that downward migration.

“Such geological conditions are not that rare,” remarked De Paoli. Several sites already meet these criteria, including regions under the ocean floor.

Experts point to defunct oil fields and saline aquifers as promising spots. 

Rocks may help or hurt carbon storage

A large question is how the rock itself reacts once carbon-laden water sneaks through its tiny channels.

Certain rocks can dissolve or shift chemically, creating new channels. Others stay intact and seal the carbon-laden water even more tightly.

Researchers are using advanced techniques to figure out if these chemical changes strengthen or weaken the rock structure. The goal is to avoid unpleasant surprises that might interfere with the permanent storage plan.

Smart ways to inject carbon water

Engineers are eyeing ways to harness this behavior for cost-effective carbon capture.

They want to design injection methods that send CO₂ straight into the sweet spot, where it will meet and merge with groundwater. Then the heavier fluid will settle deeper, away from potential fractures.

Existing industry programs in places like the Sleipner Field in the North Sea have already injected millions of tons of CO₂.

Long-running monitoring there indicates that, if done correctly, carbon stays put and shifts gradually into stable zones.

Long-term outlook

Once dissolved, carbon is far less likely to slip back to the air. The rocky overhang becomes less important once the heavy mixture has migrated downward.

Even major tremors may not nudge the fluid back to the surface after it has sunk below the seal.

This safety aspect is a primary reason many scientists want to keep exploring permanent underground CO₂ storage.

Calculations suggest there are widespread opportunities to capture and hold significant amounts of carbon over time.

Future questions

De Paoli has an ongoing project funded by the European Research Council that looks at the finer details of chemical reactions between CO₂-rich water and the rocks.

Early analysis points to possible boosts in how quickly the heavier fluid travels downward, though it varies from site to site.

These insights might help refine future carbon storage plans. If engineers know exactly how fluids mix at various depths, they can scale up designs with confidence, using data-driven methods rather than guesswork.

CO2, water, and climate change

No single solution will solve the climate puzzle. Reducing emissions, adopting clean energy, and changing the way we use resources are all still high priorities. But taking CO₂ out of the air and locking it underground might be a valuable extra measure.

As more research surfaces, scientists in this field hope to give policymakers hard data on success rates and reliable design guidelines. That could boost confidence in any large-scale adoption of this strategy.

In the United States, carbon capture projects are moving forward in industrial hubs. Similar efforts are popping up worldwide, spurred by public and private funding.

Research centers are joining forces to share knowledge about geology, fluid mechanics, and safe storage methods.

It remains to be seen whether global capacity is enough to store billions of tons of CO₂ each year. Studies aim to locate the best formations and ensure that the captured carbon never sees daylight again.

The study was published in Geophysical Research Letters.

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