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NETL Explores Sorbent-Based Direct Air Capture Systems for the Removal of Atmospheric CO2

A case study conducted by the U.S. Department of Energy’s (DOE) NETL examined the performance and cost of different sorbent-based direct air capture (DAC) system configurations that remove carbon dioxide (CO2) from the atmosphere.

DAC is an emerging carbon dioxide removal (CRD) technology that concentrates CO2 found in the ambient air rather than a large point source, thereby addressing both current and legacy emissions. Atmospheric concentrations of CO2 (~415 parts per million) are much lower than those found in effluent streams from point sources in the power and industrial sectors, presenting a greater technical and cost challenge for technologies to concentrate the CO2 to the degree necessary for storage or utilization.

DAC is a priority for the DOE and figures prominently in the Bipartisan Infrastructure Law (BIL), in which $3.5 billion has been dedicated to development of regional DAC Hubs that will each capture at least 1,000,000 metric tons of CO2 from the atmosphere. In addition, the DOE established the Carbon Negative Shot, which seeks to reduce the cost of CRD technologies to $100/net metric ton CO2 removed from the atmosphere within ten years.

“DAC has been identified as an important tool to meet the Administration’s goals of building a carbon emission-free electricity sector by 2035 and economy-wide net-zero emissions by 2050,” said Tim Fout, a member of NETL’s Strategic Systems Analysis and Engineering (SSAE) directorate. “At NETL, we’re exploring DAC technology options to lower the costs of these systems so that they can be more attractive for commercial deployment on a large scale.”

In recent years, there has been a significant increase in research focused on DAC. A number of DAC developers have advanced their proprietary technologies to small pilot-scale testing, and published performance and cost estimates; however, these technologies require further research, development, and demonstration to reduce costs. Estimates of the cost to remove CO2 from the atmosphere disclosed by various sorbent- and solvent-based DAC technology developers roughly span the range of $95–600 per ton, but varying study assumptions and inadequate detail make assessments and direct comparisons of the reported costs difficult.

This NETL study was carried out to provide an independent, highly-detailed assessment of the performance and cost of generic sorbent-based DAC system configurations, using a clear methodology.

“While the cases represented in this report are neither representative of any particular developer’s technology nor optimized for a particular sorbent material, they do provide insight into the cost of such systems and the parameters that must be improved to achieve broad viability,” said Sally Homsy, current lead NETL staff analysist for the report.

In sorbent-based DAC systems, solid sorbent filters chemically bind with CO2. Heat applied to the filters in a vacuum then causes the release of concentrated CO2, which is captured for storage or use.

Several potential process configurations were evaluated by NETL in the study. The most promising configuration examined in the study utilizes the sorbents in a monolith configuration to capture CO2 from the air while using steam and power from a natural gas combined cycle with Shell’s Cansolv system to capture CO2 from the power source, resulting in a carbon negative operational case.

NETL is a U.S. Department of Energy national laboratory that drives innovation and delivers technological solutions for an environmentally sustainable and prosperous energy future. By leveraging its world-class talent and research facilities, NETL is ensuring affordable, abundant and reliable energy that drives a robust economy and national security, while developing technologies to manage carbon across the full life cycle, enabling environmental sustainability for all Americans.