NETL expertise and oversight played a significant role in completing the first successful field test of a direct air capture (DAC) technology at the National Carbon Capture Center (NCCC).

“Results of the field test, which was completed in July at the NCCC in Wilsonville, Alabama, advanced the development of a system that has potential to lower the cost of DAC while reducing atmospheric levels of carbon dioxide (CO₂), a greenhouse gas,” said NETL’s Naomi O’Neil, federal project manager.

DAC is an emerging technology that works by processing air from the atmosphere rather than from CO₂ point sources (for instance, fossil-energy power plants and industries), thereby addressing both current and legacy emissions. DAC technologies are integral components in U.S. plans to address climate change and achieve an economy-wide net-zero-emissions economy by 2050.

The work at NCCC has been led by the Southern States Energy Board (SSEB), which received $2.5 million in federal cost-share funding to advance a project known as Direct Air Capture Recovery of Energy for CCUS Partnership (DAC RECO₂UP)from the laboratory to testing in real-world conditions at NCCC.

Other project partners included Aircapture. Located in Berkeley, California, Aircapture supplies commercial and industrial customers with clean CO₂ captured from the atmosphere and point-source emissions. Its modular DAC technology is designed for on-site application into customers’ production processes.

“The field test not only yielded data that demonstrated Aircapture’s technology can lower the cost of DAC, it also advanced the research to a technology readiness level (TRL) 5 and produced a CO₂ stream of 95% purity, which is a concentration needed to transport CO₂ for sequestration in the subsurface or use it as a feedstock to manufacture chemicals and other value-added products.” O’Neil said.

Project partners tested a solid amine sorbent-based DAC system in an environment expected to be the same as a commercial operation reflecting everyday conditions.

The technology employs a solid-amine CO₂ adsorption-desorption cycle using a honeycomb-type monolithic contactor impregnated with a solid polyethylenimine polymer that forms polymeric amine capture sites within the contactor.

A fan draws air through the contactor. CO₂ is adsorbed by the contactor via diffusion into the contactor walls. The ultra-low pressure drop monoliths maximize the efficiency of air flow, increasing mass transfer of CO₂ for adsorption. Once the sites bind sufficient quantities of CO₂, the monoliths are then exposed to vacuum and steam heat to desorb the CO₂ from the solid sorbent.

The latent heat and hydration from the steam liberates the CO₂ from the amine capture sites and acts as a sweep gas pushing the CO₂ out of the contactor toward a condenser, which condenses the steam back into water for recycle, leaving greater than 95% CO₂ gas. The CO₂ is collected, and the contactor is cooled via thermal recovery and evaporative heat loss and cycled back to adsorption mode, repeating the cycle.  

The team installed three skids (one capable of adsorbing/desorbing CO₂, an energy recovery integration skid that uses process control and heat exchangers to produce the required steam for the DAC process, and a third skid capable of compressing, liquifying and purifying the CO₂) to complete the NCCC project.

The project team tested its system for 3,300 hours over 137,000 cycles at NCCC across a range of environmental conditions and with a total available operational uptime of 94%.

NETL is a U.S. Department of Energy national laboratory that drives innovation and delivers solutions for a clean and secure energy future. By leveraging its highly skilled innovators and state-of-the-art research facilities, NETL is advancing carbon management and resource sustainability technologies to enable environmental sustainability for all Americans.