Researchers at Georgia Tech's School of Chemical and Biomolecular Engineering (ChBE) have developed a promising approach for removing carbon dioxide (CO₂) from the atmosphere to help mitigate global warming.
While promising technologies for direct air capture (DAC) have emerged over the past decade, high capital and energy costs have hindered DAC implementation.
However, in a new study published in Energy & Environmental Science, the research team demonstrated techniques for capturing CO₂ more efficiently and affordably using extremely cold air and widely available porous sorbent materials, expanding future deployment opportunities for DAC.
Harnessing Already Available Energy
The research team – including members from Oak Ridge National Laboratory in Tennessee and Jeonbuk National University and Chonnam National University in South Korea – employed a method combining DAC with the regasification of liquefied natural gas (LNG), a common industrial process that produces extremely cold temperatures.
LNG, which is a natural gas cooled into a liquid for shipping, must be warmed back into a gas before use. That warming process often uses seawater as the source of the heat and essentially wastes the low temperature energy embodied in the liquified natural gas.
Instead, by using the cold energy from LNG to chill the air, Georgia Tech researchers created a superior environment for capturing CO₂ using materials known as "physisorbents," which are porous solids that soak up gases.
Most DAC systems in use today employ amine-based materials that chemically bind CO2 from the air, but they offer relatively limited pore space for capture, degrade over time, and require substantial energy to operate effectively. Physisorbents, however, offer longer lifespans and faster CO₂ uptake but often struggle in warm, humid conditions.
The research study showed that when air is cooled to near-cryogenic temperatures for DAC, almost all of the water vapor condenses out of the air. This enables physisorbents to achieve higher CO₂ capture performance without the need for expensive water-removal steps.
"This is an exciting step forward," said Professor Ryan Lively
