“If I can, I'll quote Kennedy, who said we go to the moon not because it's easy, but because it's difficult. That's the reason we really need a holistic approach toward this complex problem." — ORNL Separations and Polymer Chemistry Section Head Sheng Dai
Researchers have been working for years to develop technology that pulls carbon dioxide out of the air.
For the most part, this work has been in the form of one-off projects conducted by relatively small research teams, with little regard to how they might be scaled up or how the carbon might be repurposed.
ORNL’s carbon effort and its combined carbon capture–separation–conversion focus area will take a different approach, coordinating physical experiments with one another and with the lab's formidable computing muscle.
Researchers will develop technology to—in the same process—remove carbon dioxide from the atmosphere, separate it from other gases and convert it into valuable products. Along the way, the project will incorporate insights from research being conducted to turn the carbon into high-level polymers (see “Making the most of captured carbon,” page 14).
“Most other places working on this are taking a more mom-and-pop approach,” said Sheng Dai, leader of the lab’s Separations and Polymer Chemistry Section. “At Oak Ridge, we’re approaching it as an interdisciplinary problem. We have materials scientists, we have chemists, we have engineers and chemical engineers, and everyone brings to the table a different expertise.”
ORNL also has some of the world’s most powerful scientific tools. These include experimental facilities such as the neutron scattering resources of the Spallation Neutron Source and High Flux Isotope Reactor and the electron microscopes and other advanced instruments at the Center for Nanophase Materials Sciences. They also include world-class computing tools such as the country's most powerful supercomputer, Summit, and the Compute and Data Environment for Science, or CADES.
The growing power of artificial intelligence and machine learning will be crucial to the project’s success. It will guide new research, of course, analyzing data as it’s being produced and creating and testing hypotheses. But it will also apply the power of artificial intelligence and data analysis to research that has been conducted in the past at ORNL and elsewhere, sifting through a mountain of data in search of new insights.
“There are certainly foundations that we can build from,” explained ORNL physical chemist Shannon Mahurin, who will be leading the research effort. “There’s been a lot of work on the separations process. For example, we know a lot of different materials that will either selectively bind or transport CO2, as a membrane or as an absorber.”
The project will also benefit from seamless communication between ORNL’s computing systems and experimental tools such as neutron scattering instruments and advanced microscopes. This coordination will allow researchers to analyze experiments as they are being conducted and even tweak them as they are taking place.
Pushing the ball forward
The carbon project will need all of these advantages to push the technology much farther than anything seen so far. Research to date has focused primarily on removing CO2 from flue gases at power plants or other carbon-intensive facilities. The potential for pulling CO2 directly out of the air has been studied less extensively.
It’s a much harder job. A power plant’s flue gas can contain upwards of 10 percent CO2; in contrast, CO2 levels in the atmosphere are a little over 400 parts per million (or about 0.0004 percent). That level may be enough to bring the carbon cycle out of balance, but it’s minuscule when you're talking about harvesting it from the atmosphere.
“From a chemistry perspective, this is tiny,” Dai said. “It’s like searching for a needle in a haystack. The sorbent needs to be very selective, very smart, and have very high capacities.”
The project is largely a materials challenge. Carbon capture relies on technologies such as sorbents, which pick up and hold a material, membranes, which allow some things through but not others, and catalysts, which enable chemical reactions but are not altered by them.
The researchers must find materials that very effectively bind CO2 without binding to other gases—especially nitrogen and oxygen, which together make up about 99 percent of the air around us. Those materials must at the same time be able to release the carbon so that it can be converted into high-level polymers and other products.
In addition, the team must find materials to do the converting. And, as Dai noted, the scale of the effort dictates that any new catalysts must rely on abundant elements rather than platinum and other noble metals.
While the challenge of capturing and processing the carbon all at the same time is enormous, the potential payoffs will also be substantial. By treating harvested CO2 not as a waste product to be stored—for instance, underground in depleted oil and gas reservoirs—but as a resource, this approach presents both environmental and economic benefits, using the carbon as an income generator rather than as a waste storage cost and opening the door to the possibility that it could pay for itself.
Difficult as the challenges are, Dai said, they’re perfect for an institution like ORNL.
“If I can, I’ll quote Kennedy, who said we go to the moon not because it's easy, but because it's difficult,” Dai said. “That’s the reason we really need a holistic approach toward this complex problem.”
