Baking soda capsules trap greenhouse gases

It is now possible to remove greenhouse gases from power-plant emissions by using sodium bicarbonate. Commonly known as baking soda, it is an ingredient found in almost every home.

Scientists at Harvard University and Lawrence Livermore National Laboratory have designed microcapsules which trap carbon dioxide (CO₂), a primary component of greenhouse gases. Each microcapsule contains a sodium bicarbonate solution, encased in a highly permeable polymer shell. The paper, recently published in the journal Nature Communications, is a pioneering advancement in carbon capture and sequestration technology.

Microcapsules are being used in various applications including biomedical engineering, drug delivery, the food industry and agriculture. These microcapsules are made using a double-capillary device to deliver carbonate-containing solution and a catalyst-enhancing CO₂ absorption into a silicone capsule shell. A catalyst causes the reaction to go faster. Molecules of sodium bicarbonate are captured in tiny droplets, providing a large surface area-to-volume ratio that increases CO₂ absorption rates. Encapsulation is a technique developed by the Department of Energy’s inaugural Advanced Research Projects Agency-Energy (ARPA-E).

“Encapsulation allows you to combine the advantages of solid capture media and liquid capture media in the same platform,” said Jennifer Lewis, professor of biologically inspired engineering at the Harvard School of Engineering and Applied Sciences and a co-lead author of the project.

Among many sources of carbon emission are volcanic eruption, fossil fuel burning, decomposition of dead materials, and power plants, all of which contribute to the largest pool of CO₂ released in the atmosphere. Global warming and ocean acidification are the major consequences of increased CO₂ emission.

“We think the microcapsule technology provides a new way to make carbon capture efficient with fewer environmental issues,” said Roger Aines, a research member of the Lawrence Livermore National Laboratory.

“Capturing the world’s carbon emissions is a huge task. We need technology that can be applied to many kinds of carbon dioxide sources with the public’s full confidence in its safety and sustainability.”

This method employs a similar framework developed in 2013 by scientists at the King Abdullah University of Science and Technology and the University of South Florida using porous materials containing unsaturated metal centers or organic amines to trap CO₂. But the capture of CO₂ using caustic amine-based solvents is expensive, low-output and toxic to the environment. The employment of sodium bicarbonate as a sorbent, in comparison, is more effective than CO₂ and is absorbed at higher rates. A major advantage of this method is that sodium bicarbonate has an infinite shelf-life, while amines disintegrate easily.  Stuart Haszeldine, a professor specializing in carbon capture and storage at the University of Edinburgh, described this innovation as “efficient, easy-to-handle, minimal waste and cheap to make.”

Encapsulation prevents the problem of corrosion as the entrapped carbonate solution does not come into contact with the inner surface of the power plant. The microcapsules allow for easy transport between absorption and release towers, even when extra CO₂ is absorbed.

Researchers from Lawrence Livermore National Laboratory and from the U.S. Department of Energy’s National Energy Technology Lab are now working to put this project to use in coal, oil and natural gas-fired power plants, as well as in industrial steel and cement manufacturing.