A new scientific review article in Nature Reviews Chemistry discusses how carbon dioxide (CO2) is converted from a gas to a solid in ultra-thin water films on underground rock surfaces. These solid minerals, known as carbonates, are both stable and common.
“As global temperatures rise, so does the urgency to find ways to store carbon,” said Lab Fellow and co-author Kevin Rosso of Pacific Northwest National Laboratory (PNNL). “By looking critically at our current understanding of carbon mineralization processes, we can find the essential gaps for the next decade of work.”
Mineralization underground is one way to release CO. to hold on2 trapped, unable to escape back into the air. But researchers must first know how it happens before they can predict and control carbonate formation in realistic systems.
“Reducing human emissions requires fundamental understanding of how to store carbon,” said PNNL chemist Quin Miller, co-lead author of the scientific review on the cover of the journal. “There is an urgent need to integrate simulations, theory and experiments to investigate problems with mineral carbonation.”
Under the ground and in the water
instead of CO. to emit2 in the air, one option is to pump it into the ground. CO . to make2 deep underground theoretically sequesters the carbon away. However, gas leaks remain a concern. But if that CO2 gas can be pumped into rocks rich in metals such as magnesium and iron, the CO2 can be converted into stable and common carbonate minerals. PNNL’s Basalt Pilot Project in Wallula is a field site dedicated to studying CO2 storage in carbonates.
While these subterranean environments are generally dominated by water, the conversion of gaseous carbon dioxide to solid carbonate can also occur when CO is injected.2 displaces that water, creating extremely thin films of residual water in contact with rocks. But these very limited systems behave differently from CO2 in contact with a puddle of water.
In thin films, the ratio of water and CO . is2 controls the response. Small amounts of metal leach from the rocks and react both in the film and on the rock surface. This leads to the creation of new carbonate materials.
Previous work led by Miller, summarized in the review, showed that magnesium behaves similarly to calcium in thin water films. The nature of the water film plays a central role in how the system reacts.
Understanding how and when these carbonates form requires a combination of laboratory experiments and theoretical modeling studies. With lab work, researchers can determine the ratio of water to CO. to coordinate2 and watch carbonates form in real time. Teams can see which specific chemicals are present at different times, providing vital information about reaction pathways.
However, laboratory work has its limits. Researchers cannot observe individual molecules or see how they interact. Chemical models can fill that gap by predicting how molecules move in great detail, making experiments a conceptual backbone. They also enable researchers to study mineralization in difficult-to-experimentally accessible conditions.
“There are important synergies between models and laboratory or field studies,” said MJ Qomi, a professor at the University of California, Irvine and co-lead author of the paper. “Experimental data grounds models in reality, while models provide a deeper understanding of experimentation.” Qomi has worked with the PNNL team for three years and plans to study carbonate mineralization in adsorbed water films.
From fundamental science to solutions
The team outlined important questions that need to be answered to make this form of carbon storage practical. Researchers need to develop knowledge about how minerals react under different conditions, especially in conditions that mimic real storage sites, including in ultra-thin water films. This must all be done through an integrated combination of modeling and laboratory experiments.
Mineralization has the potential to safely store carbon underground. Know how CO2 will react with various minerals can cause what is pumped below the surface to stay there. The fundamental scientific insights from mineralization work can lead to practical CO2 storage systems. The Basalt Pilot Project is an important research location that bridges the gap between small-scale basic science and large-scale research applications.
“This work combines a focus on fundamental geochemical insights with the goal of solving critical problems,” Miller said. “Without prioritizing decarbonization technologies, the world will continue to warm to levels that humanity cannot afford.”
Miller, Rosso and Todd Schaef were the PNNL authors of this study. This work was conducted in collaboration with MJ Qomi and Siavash Zare of the University of California, Irvine and John Kaszuba of the University of Wyoming.
Reactions that store carbon underground can cause cracks, which is good news
MJ Abdolhosseini Qomi et al, Molecular scaling mechanisms of CO2 mineralization in nanoscale interfacial water films, Nature Reviews Chemistry (2022). DOI: 10.1038/s41570-022-00418-1
Quote: Converting carbon dioxide to solid minerals underground for more stable storage (2022, October 19) retrieved October 19, 2022 from https://phys.org/news/2022-10-carbon-dioxide-solid-minerals-underground.html
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