Scientists at the Department of Energy’s Oak Ridge National Laboratory have found a simple, reliable process to capture carbon dioxide directly from ambient air, offering a new option for carbon capture and storage strategies to combat global warming.
Initially, the ORNL team was studying methods to remove environmental contaminants such as sulfate, chromate or phosphate from water. To remove those negatively charged ions, the researchers synthesized a simple compound known as guanidine designed to bind strongly to the contaminants and form insoluble crystals that are easily separated from water.
In the process, they discovered a method to capture and release carbon dioxide that requires minimal energy and chemical input. Their results are published in the journal Angewandte Chemie International Edition.
“When we left an aqueous solution of the guanidine open to air, beautiful prism-like crystals started to form,” ORNL’s Radu Custelcean said. “After analyzing their structure by X-ray diffraction, we were surprised to find the crystals contained carbonate, which forms when carbon dioxide from air reacts with water.”
Decades of research has led to the development of carbon capture and long-term storage strategies to lessen the output or remove power plants’ emissions of carbon dioxide, a heat-trapping greenhouse gas contributing to a global rise in temperatures. Carbon capture and storage strategies comprise an integrated system of technologies that collects carbon dioxide from the point of release or directly from the air, then transports and stores it at designated locations.
A less traditional method that absorbs carbon dioxide already present in the atmosphere, called direct air capture, is the focus of ORNL’s research described in this paper, although it could also be used at the point where carbon dioxide is emitted.
Once carbon dioxide is captured, it needs to be released from the compound so the gas can be transported, usually through a pipeline, and injected deep underground for storage. Traditional direct air capture materials must be heated up to 900 degrees Celsius to release the gas — a process that often emits more carbon dioxide than initially removed. The ORNL-developed guanidine material offers a less energy-intensive alternative.
“Through our process, we were able to release the bound carbon dioxide by heating the crystals at 80-120 degrees Celsius, which is relatively mild when compared with current methods,” Custelcean said. After heating, the crystals reverted to the original guanidine material. The recovered compound was recycled through three consecutive carbon capture and release cycles.
While the direct air capture method is gaining traction, according to Custelcean, the process needs to be further developed and aggressively implemented to be effective in combatting global warming. Also, they need to gain a better understanding of the guanidine material and how it could benefit existing and future carbon capture and storage applications.
The research team is now studying the material’s crystalline structure and properties with the unique neutron scattering capabilities at ORNL’s Spallation Neutron Source (SNS), a DOE Office of Science User Facility. By analyzing carbonate binding in the crystals, they hope to better understand the molecular mechanism of carbon dioxide capture and release and help design the next generation of sorbents.
The scientists also plan to evaluate the use of solar energy as a sustainable heat source to release the bound carbon dioxide from the crystals.
Researchers have successfully turned carbon dioxide into solid rock by injecting it into ancient lava flows
For the first time, scientists have injected carbon dioxide into ancient lava flows and watched it solidify, demonstrating that capturing carbon dioxide from the atmosphere or a power plant smokestack and safely storing it underground may be a realistic way to help reduce greenhouse gas emissions to tackle climate change, according to research published Friday.
Scientists working at the Wallula Basalt Pilot Project in Washington State turned liquefied carbon dioxide into solid rock by injecting the gas into basalt formations. Over a span of about two years, the carbon dioxide solidified into a mineral called ankerite, according to the study conducted by Pacific Northwest National Laboratory researchers. The research was published in the journal Environmental Science and Technology.
“This study further supports the idea that one of the major rock types on the planet—basalts—can be used to store carbon dioxide permanently and safely,” said study lead author Pete McGrail, a carbon dioxide and climate change researcher at PNNL.
Carbon capture and storage may be critical to helping prevent global warming from exceeding 2°C (3.6°F), either by capturing emissions from their source or by directly removing carbon dioxide from the atmosphere, according to the Intergovernmental Panel on Climate Change.
But scientists worry that storing captured carbon underground as a liquid or a gas may not be safe because stored carbon dioxide could explosively leak into the atmosphere through fissures in the earth or be exposed to terrorism risk, creating a climate catastrophe.
To solve that problem, researchers have been studying ways to store carbon dioxide underground as a solid, especially in basalt formations.
Basalt is a volcanic rock that makes up roughly 70 percent of the earth’s surface. When it is exposed to carbon dioxide and water, a chemical reaction occurs, converting the gas to a chalk-like solid material. Scientists previously thought the chemical reaction would take thousands of years to occur, but new research shows it can happen within a few years.
“Basalt storage is unique in the geologic sequestration of carbon dioxide because the principal trapping mechanism is a chemical reaction that locks the carbon dioxide away as a carbonate mineral that can never leak or return to the atmosphere,” McGrail said.
Earlier this year, researchers at the CarbFix project in Iceland were able to pump a geothermal power plant’s carbon dioxide-rich volcanic gases into deep underground but recently formed basalt formations and chemically solidify them in about two years.
An international team of scientists have found a potentially viable way to remove anthropogenic (caused or influenced by humans) carbon dioxide emissions from the atmosphere – turn it into rock.
The study, published today in Science, has shown for the first time that the greenhouse gas carbon dioxide (CO2) can be permanently and rapidly locked away from the atmosphere, by injecting it into volcanic bedrock. The CO2 reacts with the surrounding rock, forming environmentally benign minerals.
Measures to tackle the problem of increasing greenhouse gas emissions and resultant climate change are numerous. One approach is Carbon Capture and Storage (CCS), where CO2 is physically removed from the atmosphere and trapped underground. Geoengineers have long explored the possibility of sealing CO2 gas in voids underground, such as in abandoned oil and gas reservoirs, but these are susceptible to leakage. So attention has now turned to the mineralisation of carbon to permanently dispose of CO2.
Until now it was thought that this process would take several hundreds to thousands of years and is therefore not a practical option. But the current study – led by Columbia University, University of Iceland, University of Toulouse and Reykjavik Energy – has demonstrated that it can take as little as two years.
The new building material could transform polluting emissions into a valuable resource
Imagine a world with little or no concrete. Would that even be possible? After all, concrete is everywhere — on our roads, our driveways, in our homes, bridges and buildings. For the past 200 years, it’s been the very foundation of much of our planet.
But the production of cement, which when mixed with water forms the binding agent in concrete, is also one of the biggest contributors to greenhouse gas emissions. In fact, about 5 percent of the planet’s greenhouse gas emissions comes from concrete.
An even larger source of carbon dioxide emissions is flue gas emitted from smokestacks at power plants around the world. Carbon emissions from those plants are the largest source of harmful global greenhouse gas in the world.
A team of interdisciplinary researchers at UCLA has been working on a unique solution that may help eliminate these sources of greenhouse gases. Their plan would be to create a closed-loop process: capturing carbon from power plant smokestacks and using it to create a new building material — CO2NCRETE — that would be fabricated using 3D printers. That’s “upcycling.”
“What this technology does is take something that we have viewed as a nuisance — carbon dioxide that’s emitted from smokestacks — and turn it into something valuable,” said J.R. DeShazo, professor of public policy at the UCLA Luskin School of Public Affairs and director of the UCLA Luskin Center for Innovation.
“I decided to get involved in this project because it could be a game-changer for climate policy,” DeShazo said. “This technology tackles global climate change, which is one of the biggest challenges that society faces now and will face over the next century.”
DeShazo has provided the public policy and economic guidance for this research. The scientific contributions have been led by Gaurav Sant, associate professor and Henry Samueli Fellow in Civil and Environmental Engineering; Richard Kaner, distinguished professor in chemistry and biochemistry, and materials science and engineering; Laurent Pilon, professor in mechanical and aerospace engineering and bioengineering; and Matthieu Bauchy, assistant professor in civil and environmental engineering.
This isn’t the first attempt to capture carbon emissions from power plants. It’s been done before, but the challenge has been what to do with the carbon dioxide once it’s captured.
“We hope to not only capture more gas,” DeShazo said, “but we’re going to take that gas and, instead of storing it, which is the current approach, we’re going to try to use it to create a new kind of building material that will replace cement.”
“The approach we are trying to propose is you look at carbon dioxide as a resource — a resource you can reutilize,” Sant said. “While cement production results in carbon dioxide, just as the production of coal or the production of natural gas does, if we can reutilize CO2 to make a building material which would be a new kind of cement, that’s an opportunity.”
The researchers are excited about the possibility of reducing greenhouse gas in the U.S., especially in regions where coal-fired power plants are abundant. “But even more so is the promise to reduce the emissions in China and India,” DeShazo said. “China is currently the largest greenhouse gas producer in the world, and India will soon be number two, surpassing us.”
Thus far, the new construction material has been produced only at a lab scale, using 3-D printers to shape it into tiny cones. “We have proof of concept that we can do this,” DeShazo said. “But we need to begin the process of increasing the volume of material and then think about how to pilot it commercially. It’s one thing to prove these technologies in the laboratory. It’s another to take them out into the field and see how they work under real-world conditions.”
“We can demonstrate a process where we take lime and combine it with carbon dioxide to produce a cement-like material,” Sant said. “The big challenge we foresee with this is we’re not just trying to develop a building material. We’re trying to develop a process solution, an integrated technology which goes right from CO2 to a finished product.
“3-D printing has been done for some time in the biomedical world,” Sant said, “but when you do it in a biomedical setting, you’re interested in resolution. You’re interested in precision. In construction, all of these things are important but not at the same scale. There is a scale challenge, because rather than print something that’s 5 centimeters long, we want to be able to print a beam that’s 5 meters long. The size scalability is a really important part.”
Another challenge is convincing stakeholders that a cosmic shift like the researchers are proposing is beneficial — not just for the planet, but for them, too.
“This technology could change the economic incentives associated with these power plants in their operations and turn the smokestack flue gas into a resource countries can use, to build up their cities, extend their road systems,” DeShazo said. “It takes what was a problem and turns it into a benefit in products and services that are going to be very much needed and valued in places like India and China.”
It could be the key to large-scale implementation of carbon capture
Carbon capture is a process by which waste carbon dioxide (CO2) released by factories and power plants is collected and stored away, in order to reduce global carbon emissions. There are two major ways of carbon capture today, one using powder-like solid materials which “stick” to CO2, and one using liquids that absorb it. Despite their potential environmental and energy benefits, current carbon capture strategies are prohibitive because of engineering demands, cost and overall energy-efficiency. Collaborating scientists from EPFL, UC Berkley and Beijing have combined carbon-capturing solids and liquids to develop a “slurry” that offers the best of both worlds: as a liquid it is relatively simple to implement on a large scale, while it maintains the lower costs and energy efficiency of a solid carbon-capturing material. The breakthrough method is published in Nature Communications.
The most common approach to carbon capture uses liquid amine solutions, which can absorb CO2 from the atmosphere. On a large scale, the system uses two columns, one for capturing CO2 and the other for releasing it from the liquid, in a process referred to as “regeneration”. For amine solutions, regeneration is the most energy-consuming part because the CO2 is so strongly bound to the amine molecules that it is necessary to actually boil them in order to separate them.
An alternative to liquids is to use solid materials known as “metal-organic frameworks” (MOFs). These are fine powders whose particles are made up of metal atoms that are connected into a 3D structure with organic linkers. Their surface is covered with nano-size pores that collect CO2 molecules. But despite its lower cost, as this method involves transporting solids it is very demanding in terms of engineering. Berend Smit, Director of the Energy Center at EPFL, explains: “Imagine trying to walk with a plateful of baby powder. It’s going to go everywhere, and it’s very difficult to control.”
Working with scientists from Beijing and UC Berkeley, Smit is a lead author on a breakthrough carbon-capture innovation that uses a mixture of solid and liquid in solution called a “slurry”. The solid part of the slurry is a MOF called ZIF-8, which is suspended in a 2-methylimidazole glycol liquid mixture.
“Why a slurry?” says Smit. “Because in the materials that are currently used for adsorption the pores are too large and the surrounding liquid would fill them, and not let them capture CO2 molecules. So here we looked at a material – ZIF-8 – whose pores are too small for the glycol’s molecules to fit, but big enough for capturing the CO2 molecules from flue gas.”
ZIF-8 is a good material for carbon-capturing slurries, because it displays excellent solution, chemical and thermal stability, which is important for repeated regeneration cycles. ZIF-8 crystals have narrow pores (3.4 Å in diameter) that are smaller than the diameter of glycol molecules (4.5 Å), preventing them from entering. Even though other liquids were tested in the design of the slurry, including ethanol, hexane, methylbenzene and tetrachloromethane, their molecules are small enough to enter the ZIF-8 pores and reduce its carbon capturing efficiency. In this respect, glycerol has so far been shown to be an ideal liquid.