An Emerging Technique for Captured Carbon Conversion

By Hamilton Waldron

A new method of carbon capture could help the nation’s coal plants reduce greenhouse gas emissions and take one step closer toward the industry’s long-term goal of converting captured carbon into a useable product, but economic obstacles currently impede full implementation of this promising technology.

Rethinking How Carbon is Reused

U.S. Department of Energy scientists at the Idaho National Laboratory (INL) established the process for converting captured carbon dioxide (CO₂) into syngas, a combination of hydrogen (H₂) and carbon monoxide (CO) that can be used to create fuels and chemicals. When the team of researchers recently published its findings, it noted that, “for the first time, it was demonstrated that syngas can be directly produced from captured CO₂ — eliminating the requirement of downstream separations.”

The Art of Carbon Conversion

Typically, the method for capturing the carbon from CO₂ involves a reduction step that requires high temperatures and pressures. This is because CO₂ does not stay dissolved in water for a sufficient period to enable capture after its temperature has been lowered. The new process addresses this challenge by using specialized switchable polarity solvents (SPS) that help make the CO₂ more soluble and allow the carbon capture medium to be added to a cell for electrochemical conversion to syngas.

Too Much Hydrogen, Not Enough Syngas

In 2017, the researchers at the INL were granted Laboratory Directed Research and Development funds to begin their study. Shortly after the first round of experiments, however, they found that too much hydrogen and not enough syngas were being produced. The team then added a supporting electrolyte (potassium sulfate) to increase ionic conductivity, which produced the expected amounts of syngas almost instantaneously.

Next Steps: Improved Industrial Application

Once syngas can be produced competently and consistently from captured CO₂, options for using this new methodology in industrial applications will greatly expand. The SPS-based process proved optimal at ambient temperature (25^oC) and 40 psi, after all, in sharp contrast with previous processes that required high temperatures and pressures.

Additionally, the INL has filed for a provisional patent and is discussing its methods with a Boston-based company that specializes in electrochemical technology development. “It integrates two areas that have been on parallel tracks: carbon capture and sequestration (CCS) and CO₂ utilization,” said Diaz Aldana, a researcher at INL. “The problem with CCS has been its economic feasibility. If you can get some extra value out of the CO₂ you are capturing, it's a different story.”