Peering Inside Carbon-Storing Rocks
As scientists search for reliable ways to reduce greenhouse gases, underground carbon storage has become an important strategy. Recently, researchers at the Massachusetts Institute of Technology used advanced X-ray imaging to examine how volcanic rocks could store captured carbon dioxide (CO₂). By analyzing basalt samples with high-resolution scans, the team was able to see how CO₂-rich fluids move through the rock and how much carbon the formation might ultimately hold.
Basalt, a volcanic rock commonly found in places like Iceland and Hawaii, contains numerous microscopic pores and fractures. Because of these tiny pathways, fluids can travel through the rock relatively easily. As a result, basalt has emerged as a promising candidate for storing CO₂ captured from power plants and industrial facilities.
When Carbon Turns Into Stone
When CO₂ dissolves in water and flows through basalt, a chemical reaction begins. Minerals in the rock—such as calcium, magnesium, and iron—react with the dissolved gas. Gradually, these reactions form solid carbonate minerals like calcite. In effect, the carbon becomes locked into stone, preventing it from escaping back into the atmosphere.
In fact, previous projects in Iceland have shown how effective this process can be. Researchers found that most injected CO₂ mineralized within only a few years, demonstrating that volcanic rocks can permanently store large amounts of carbon.
What X-Ray Imaging Revealed
To better understand this transformation, scientists scanned basalt samples using CT-style X-ray technology. Through these images, they tracked how minerals formed inside the rock over time. The scans showed that mineral deposits first appeared in tiny micro-fractures connecting larger pores. Consequently, these deposits gradually reduced the rock’s permeability, meaning fluids flowed more slowly through it.
However, the overall pore space changed very little during the experiments. Only a small fraction of the rock’s internal volume filled with minerals, suggesting that basalt formations may continue storing carbon for long periods.
A Tool for Monitoring Underground Storage
Researchers also discovered that ultrasonic signals can detect structural changes in the rock as mineralization progresses. Therefore, seismic monitoring could help scientists estimate how much CO₂ has been stored underground without drilling additional wells.
Overall, the findings suggest that vast basalt formations around the world could become secure, long-term reservoirs for captured carbon—helping reduce emissions and support global climate goals.
