Will carbon capture ever see daylight? Electrochemical carbon capture

Researchers: Yupo Lin, Richard Doctor, and Seth Snyder from Argonne National Laboratory, Jitendra Shah from Nalco Company

Researchers made breakthroughs in an innovative ARPA-E funded carbon capture technology just as the rise of natural gas, with its low carbon output, sank the carbon capture market. However, developers see potential in overseas markets like coal-heavy China and India, as well as promising applications unrelated to clean energy, such as organic acid production for industrial use.

The researchers used an enzyme found in all living cells as the key to capturing carbon from flue gas, the gas released as exhaust from power plants. The enzyme, called carbonic anhydrase (CA), is found in such places as the human lung where it helps remove carbon dioxide from tissues. Researchers at Argonne National Laboratory and Nalco Company took advantage of the CO2-processing ability of CA for the carbon capture application.

Funded by an ARPA-E grant of $2.25 million, Yupo Lin, Richard Doctor, and Seth Snyder from Argonne National Laboratory and Jitendra Shah from Nalco Company designed an apparatus that takes in CO2-laden gas, removes CO2 through an electrochemical process, and expels the clean gas and CO2 separately.

The patented technology, called resin wafer electrodeionization (RW-EDI), makes use of small swings in pH under the presence of the enzyme to drive its reactions at low electricity. Previous technologies required use of vacuum or heat, which are electricity-intensive. Lowering the electricity requirement lowers the cost of the technology as well as the carbon footprint, which is the initial objective of the apparatus.

“All reactions need two things: you need a driving force of thermodynamics, something that’s going to make it want to go in a certain direction, and kinetics, you need the rate to be fast enough,” Snyder said. Changing pH drives the removal of CO2 from the gas, and CA speeds up the kinetics, or rate, of the reaction.

A good way to visualize the role of CA in this apparatus is to open a can of coke. The CO2 bubbles rise to the surface, but the drink remains fizzy for a long time. This is because the kinetics of CO2 dissolving into air is slow. Adding the enzyme is akin to the can of coke going flat in seconds. The enzyme speeds up the reaction of CO2 dissolving into solution.

A commercial-size model, which fits in a 20 by 20 foot room, has the capacity to process the flue gas from a 250 MW power plant – enough to power 190,500 homes.

A challenge the team ran into was the cost of CA.

“Something that costs dollars per milligram, that you’re going to use on the ton scale, is not going to be a commercially viable process,” said Snyder, adding that additional research could cut the cost of the enzyme or lead to development of an inorganic catalyst.

Without an appropriate amount of catalyst, the electricity requirements of the apparatus are high, which is the original problem the project was aiming to solve, explained Jitendra Shah, principle investigator of the team at Nalco Company.

“Nobody is able to come up with a cost-effective technology for CO2 removal, and nobody’s really practicing it because there are no regulations and there are no cost-effective methods,” Shah said. “So it’s still quite an expensive technology at this point.”

Though they did not resolve cost issues with the enzyme catalyst, the RW-EDI technology, as a platform technology, is versatile and can be adapted to different technologies, including those unrelated to clean energy. Similar to how a hanger can be used not only to hang your clothes but also unlock your car door, the basic design of the RW-EDI hardware is suitable for other applications, such as the production of organic acid, which is widely used in industrial applications.

The research team also has a long term vision for the technology. Yupo Lin, principle investigator at Argonne National Laboratory, explained that other than carbon capture and organic acid production, the researchers have a long-term vision for using the technology in converting carbon dioxide into fuel. However, that likely will be a decade down the line in development. “Carbon dioxide [capture] is one of the short-term” visions for the technology, Lin said.

Another possibility is the transfer of the technology overseas in coal-dependent countries such as China and India. China attains 70 percent of its energy from coal, and with its energy requirements constantly expanding, it’s pressed to find a way to clean up its air.

However, with ARPA-E funding of the project at an end, it remains to be seen whether this technology will be picked up for further development.


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