Can clay capture carbon dioxide?

The atmospheric level of carbon dioxide — a gas that is great at trapping heat, contributing to climate change — is almost double what it was prior to the Industrial Revolution, yet it only constitutes 0.0415% of the air we breathe.

This presents a challenge to researchers attempting to design artificial trees or other methods of capturing carbon dioxide directly from the air. That challenge is one a Sandia National Laboratories-led team of scientists is attempting to solve.

Led by Sandia chemical engineer Tuan Ho, the team has been using powerful computer models combined with laboratory experiments to study how a kind of clay can soak up carbon dioxide and store it.

The scientists shared their initial findings in a paper published earlier this week in The Journal of Physical Chemistry Letters.

“These fundamental findings have potential for direct-air capture; that is what we’re working toward,” said Ho, lead author on the paper. “Clay is really inexpensive and abundant in nature. That should allow us to reduce the cost of direct-air carbon capture significantly, if this high-risk, high-reward project ultimately leads to a technology.”

Why capture carbon?

Carbon capture and sequestration is the process of capturing excess carbon dioxide from the Earth’s atmosphere and storing it deep underground with the aim of reducing the impacts of climate change such as more frequent severe storms, rising sea levels and increased droughts and wildfires. This carbon dioxide could be captured from fossil-fuel-burning power plants, or other industrial facilities such as cement kilns, or directly from the air, which is more technologically challenging. Carbon capture and sequestration is widely considered one of the least controversial technologies being considered for climate intervention.

“We would like low-cost energy, without ruining the environment,” said Susan Rempe, a Sandia bioengineer and senior scientist on the project. “We can live in a way that doesn’t produce as much carbon dioxide, but we can’t control what our neighbors do. Direct-air carbon capture is important for reducing the amount of carbon dioxide in the air and mitigating the carbon dioxide our neighbors release.”

Ho imagines that clay-based devices could be used like sponges to soak up carbon dioxide, and then the carbon dioxide could be “squeezed” out of the sponge and pumped deep underground. Or the clay could be used more like a filter to capture carbon dioxide from the air for storage.

In addition to being cheap and widely available, clay is also stable and has a high surface area — it is comprised of many microscopic particles that in turn have cracks and crevasses about a hundred thousand times smaller than the diameter of a human hair. These tiny cavities are called nanopores, and chemical properties can change within these nanoscale pores, Rempe said.

This is not the first time Rempe has studied nanostructured materials for capturing carbon dioxide. In fact, she is part of a team that studied a biological catalyst for converting carbon dioxide into water-stable bicarbonate, tailored a thin, nanostructured membrane to protect the biological catalyst and received a patent for their bio-inspired, carbon-catching membrane. Of course, this membrane is not made out of inexpensive clay, and was initially designed to work at fossil-fuel-burning power plants or other industrial facilities, Rempe said.

“These are two complementary possible solutions to the same problem,” she said.

Read the complete news release.

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