Schematic of the BIG-based carbon capture process. Source: ORNL

A new class of organic compounds engineered at U.S. Oak Ridge National Laboratory (ORNL) captures carbon from coal-fired power plant emissions in a process that is less energy-intensive than existing methods.

The material is based on bis-iminoguanidines (BIGs) that selectively bind specific anions, a property exploited in the development of an aqueous BIG solution with bicarbonate ions in a carbon dioxide (CO₂) separation cycle. As flue gas is piped through the solution, CO₂ molecules bind to the BIG sorbent which crystallizes into a solid bicarbonate salt. The solids are filtered out of the solution and heated at 120° C to release the CO₂ so it can be sent to permanent storage. The solid sorbent can then be dissolved in water and reused in the process indefinitely.

The method consumes about 24% less energy relative to available sorbent-based emission control systems, which may require higher heating temperatures. No sorbent loss was observed after ten consecutive cycles.

Efforts are now focused on improving scalability of the carbon capture process, which is currently constrained by a relatively low CO₂ capacity and absorption rate due to the limited solubility of the BIG sorbent in water. A research paper on the carbon capture sorbent is published in Cell Press.