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Greenhouse Gases

New process could bring down cost of direct carbon capture

A peptide-guanidine system soaks up CO2 from air and can be regenerated with mild heat

by Prachi Patel, special to C&EN
April 3, 2021 | A version of this story appeared in Volume 99, Issue 12


Structures of peptides and guanadine.

A new technique to capture carbon dioxide from the air could be less expensive and use less energy than today’s technologies (Cell Rep. Phys. Sci. 2021, DOI: 10.1016/j.xcrp.2021.100385). Direct air capture could play a key role in meeting climate targets. Today’s systems pass air over aqueous hydroxide solutions or solid amine-based sorbents that react with CO2. Releasing the gas to regenerate these materials requires a lot of energy. Radu Custelcean and colleagues at Oak Ridge National Laboratory decided to use a peptide solution instead. After all, these short amino acid chains also contain amine groups that can react with CO2, and those reactions convert CO2 to bicarbonate ions. The researchers then added a guanidine compound, which scavenges protons and bicarbonate ions, recovering the amino acids and forming guanidine-carbonate crystals. Mildly heating the crystals restores the guanidine and releases the CO2 for storage or use. Custelcean says the team’s analysis shows the cost should be comparable or lower than the state of the art options. Peptides and guanidines are inexpensive, and the new method requires lower heating temperatures than traditional liquid or solid amines. It uses just 3.45 GJ of energy per ton of captured CO2, versus the 5–10 GJ required for existing technologies. The team is licensing the technology to a start-up for commercialization.


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