Developed at Lehigh University, new filter technology effectively captures “ultradilute” CO2 in the air you breathe. In the future, renewable energy-powered systems may be able to use seawater, convert it, and store it safely.
Lehi Engineering researcher Arup Sengupta has developed a new method to capture carbon dioxide from the air and store it in an “infinite sink” in the ocean.
This approach uses an innovative copper-containing polymer filter that essentially converts CO2 into sodium bicarbonate (aka baking soda) that can be released harmlessly into the ocean. This new hybrid material or filter, called DeCarbonHIX (decarbonization with hybrid ion-exchange materials), is described in a recent paper published in Science Advances.
Demonstrating a 300% increase in the amount of carbon captured compared to existing direct air capture methods, the study was published in media such as the BBC, CNN, Fast Company, The Daily Beast, and the American Chemical Society. SenGupta himself has drawn interest in the technology from companies based in Brazil, Ireland, and the Middle East.
“The climate crisis is a global issue,” says Sengupta, professor of chemical and biomolecular engineering and civil and environmental engineering at PC Rossin College of Engineering and Applied Sciences in Lehi. “And we believe we have a responsibility to build direct air capture technology in a way that people and countries around the world can do. Anyone who can operate a mobile phone should be able to operate this process.” This is not technology to make money, it’s to save the world.”
This work is yet another extension of SenGupta’s personal and professional commitment to developing technologies that benefit humanity, especially marginalized communities around the world. His research in water science and technology includes drinking water treatment methodologies, desalination, municipal wastewater reuse, and resource recovery. He invented the first reusable arsenic-selective hybrid anion exchanger nanomaterial (HAIX-Nano), resulting in more than 2 million of his people worldwide drinking arsenic-safe water. became. Two of his patents are recognized as “patents for mankind” by the US Patent and Trademark Office.
His DeCarbonHIX invention was the result of an ongoing CO2-driven wastewater desalination project funded by the Bureau of Reclamation under the U.S. Department of the Interior. SenGupta and his students were on the lookout to ensure that his CO2 could be delivered remotely. That quest led to the field of Direct Air Capture (DAC) and the creation of DeCarbonHIX. This topic was the subject of his Hao Chen ’23 PhD dissertation, an environmental engineering student. He successfully defended his PhD in March and plans to complete his PhD in May.
Carbon capture at low concentrations
Carbon dioxide is the most common greenhouse gas that causes global warming. According to the International Energy Agency, global CO2 emissions in 2021 will reach 36.3 gigatonnes, up 6% from the previous year. Just 1 gigaton (equivalent to 1 billion tons) is equivalent to the mass of all land mammals on Earth.
According to the Intergovernmental Panel on Climate Change, greenhouse gas emissions have warmed the world by about 1.1 degrees Celsius above pre-industrial levels. The IPCC, in its 2021 working group report, forecasts an average annual temperature increase of at least 1.5 degrees Celsius over the next 20 years. The warmer the planet, the greater the impacts of rising sea levels, extreme storms, and ecological disruption, all of which affect global health, safety, and stability.
“The worst part of this crisis is that the marginalized poor suffer ten times more than those who contributed to this situation,” says SenGupta.
He says there are three ways to reduce CO2. The first government action can reduce emissions, but it doesn’t address what’s already in the air.
“The second method is to remove carbon dioxide from point sources such as chimneys and chimneys, where large amounts of carbon dioxide are emitted,” he says. “The nice thing about this is that it can be removed at very high concentrations, but only for emissions from specific sources.”
The newest method, called direct air capture, “can remove CO2 from anywhere, including your own backyard,” he says.
In DAC, a chemical process removes atmospheric CO2, which is then typically stored underground. But SenGupta said the technology is limited by capacity. Not enough CO2 can be captured to overcome the energy costs of running the process.
“If you’re capturing carbon dioxide through the stacks of your plant, the amount of CO2 in the air can exceed 100,000 ppm,” he says. “At that concentration, we can easily remove it. But generally speaking, the CO2 level in the air is around 400 ppm. It is considered ultra-dilute and cannot be collected sufficiently by current filter materials.”
Another DAC challenge is storage. After the CO2 is captured, it is melted, pressurized, liquefied and stored, typically several miles underground. DAC operations should be located in areas with adequate geological storage and stability. For example, countries like Japan cannot pump CO2 underground because the region is earthquake-prone.
find a solution in seawater
SenGupta has developed a DAC method that overcomes both capture and storage issues.
For capture problems, he developed DeCarbonHIX, which contains copper.
“Copper changes the intrinsic properties of the parent polymer material, increasing its scavenging capacity by 300%,” he says. “We have shown that capacity can be achieved by capturing air directly from air containing 400 ppm CO2, meaning capacity is no longer a function of the amount of carbon dioxide in the air. It saturates perfectly even in concentrations, so you can run DAC in your backyard, in the middle of the desert, or in the middle of the ocean.”
Sea is indeed SenGupta’s solution to the storage problem. His DAC process begins by blowing air through a filter to capture his CO2. When the filter is saturated with gas molecules (determined by measuring the amount of gas entering and exiting the filter), seawater passes through the filter. Seawater converts carbon dioxide to sodium bicarbonate (you may know it as baking soda, but we’re talking about a dissolved solution here, so it’s not visually noticeable). The dissolved sodium bicarbonate is discharged directly into the ocean, which Sengupta calls an “infinite sink.”
“And it has absolutely no negative impact on the ocean,” says Sengupta. “The salinity does not change at all.”
In fact, the slightly alkaline sodium bicarbonate could improve ocean health, he says. This is because the rising concentration of CO2 in his atmosphere gradually lowered the pH of the ocean, causing acidification. More acidic water can harm the growth and reproduction of marine life such as corals and plankton, causing a catastrophic collapse in the food chain.
“Sodium bicarbonate can reverse the drop in pH,” he says.
Like existing DAC processes, DeCarbonHIX can also be desorbed with hydrothermal or steam, he said, allowing pure CO2 to be captured, compressed, and stored in underground geological reservoirs.
“In effect, this new filter material offers a dual mode of desorption and isolation.”
Add renewable energy to the mix
The third part of SenGupta’s innovative method conditions the filter, essentially returning it to a state where it can start capturing CO2 again. (In other words, clean it.) The process requires running a dilute solution of sodium hydroxide through the filter.
“The question is, where does this sodium hydroxide come from? In many places, it may already be a waste product, but sodium hydroxide can also be made using seawater, and its production The energy we need can come from renewable sources such as solar, wind, etc. If the goal is to remove CO2, the process should emit as little CO2 as possible. It’s about net zero direct air capture.”
SenGupta envisions a sort of offshore platform that hosts the entire operation. As air blows, the filter traps carbon dioxide until it saturates, at which point seawater converts the gas into a sodium bicarbonate solution, and the sodium hydroxide produced from the seawater returns the filter to working condition. Everything is powered by energy from waves, wind, and/or the sun. Such platforms will be widely deployed in a universal effort to capture 100 million tonnes of CO2 in 5 to 7 years.
“Scale is important here,” he says. “And it’s on a scale never before dealt with in the history of human civilization. I just did this in the lab.”
Building this technology to the level of true global impact presents a major engineering challenge, requiring expertise and partnerships across many disciplines and, of course, funding.
“This is clearly not magic,” he says. “There will be a lot of problems that we will have to solve along the way.
But I believe it can be a very economical process. ”
Original: The path to net-zero carbon capture and storage could lead to the ocean
Than: Lehigh University
