New Electrochemical Device Captures CO2 Using Less Energy

A lab-scale carbon capture device that moves CO2 across a battery-like cell used electricity at a rate of about 0.8 megawatt-hours per ton of captured CO2, according to a study led by James Buchen of the University of Delaware and published in Nature Energy, as reported by Ars Technica. Current direct-air-capture facilities run in the range of 1.5 to 3 megawatt-hours per ton of CO2, per the same study — meaning the new design used roughly half to a quarter of the energy of existing systems in this test.

How much energy does the new device use?

The headline figure is 0.8 megawatt-hours per ton of CO2 pulled from the air, measured on a nine-cell stack built by Buchen's team, Ars Technica reported. Each cell had an area of roughly half a letter-sized sheet of paper. By comparison, facilities using today's dominant approach — passing air through a reversible chemical filter that is later heated to release the trapped gas — consume 1.5 to 3 megawatt-hours per ton, according to the study. Energy use matters directly to cost: capturing carbon dioxide from ambient air is one of the more expensive climate technologies now being commercialized, largely because of the electricity or heat needed to strip the gas back out of the capture medium.

How does the battery-based system work?

The device relies on nickel hydroxide electrodes — the same material used in the cathode of older rechargeable nickel-metal hydride AA and AAA batteries, Ars Technica reported. Applying a voltage drives one electrode, the cathode, to produce hydroxide ions. Those ions react with CO2 in the air, converting it into carbonate or bicarbonate, which then passes through a separator membrane to the other electrode, the anode. There, lower pH conditions reverse the chemistry, releasing the CO2 as gas that can be collected.

The mechanism functions less like a battery being charged for later use and more like what Ars Technica described as "a chemical seesaw": reverse the applied voltage and the anode and cathode swap roles, running the identical chemistry backward. A blower — using parts borrowed from fuel cell design — pushes air through channels in plates that sandwich each cell, keeping gas moving across the stack the entire time it operates.

Who built the device and is it headed to market?

Several members of the research team are affiliated with RepAir Carbon, a startup built around this technology, Ars Technica reported. The published study includes discussion of piloting the process, according to the outlet, indicating the group is already working toward moving the concept beyond the lab-scale, nine-cell unit tested in the Nature Energy paper. Ars Technica's report does not specify a timeline, funding amount, or planned capture capacity for any pilot facility.

How does this compare with existing carbon capture technology?

Most operating direct-air-capture equipment uses a filter-based cycle: air passes through granules or a liquid absorbent that binds CO2, and a separate heating step later drives the gas back off so it can be collected and stored or used, Ars Technica reported. That heating step is typically the largest energy cost in the process. The electrochemical design tested by Buchen's team swaps thermal desorption for an applied voltage, moving CO2 across a membrane rather than heating an entire absorbent bed. The reported gap — 0.8 megawatt-hours per ton versus 1.5 to 3 megawatt-hours per ton for current facilities — is the central efficiency claim in the study, though it comes from a small lab prototype rather than a commercial-scale plant.

What happens next for the technology?

The study frames the nine-cell stack as a proof of concept rather than a deployable product, and Ars Technica's account notes the paper devotes attention to sketching out plans for piloting the process at RepAir Carbon. Scaling any capture technology from a half-letter-page-sized cell to a facility processing meaningful tons of CO2 typically raises new questions about durability, manufacturing cost, and whether energy savings measured in the lab hold up at industrial volume — questions the current paper, as summarized by Ars Technica, does not yet answer.

For now, the reported figures give the clearest available comparison point: an electrochemical cell using nickel hydroxide electrodes to shuttle carbon dioxide across a membrane at roughly a third to half the energy cost of the filter-and-heat systems that dominate the direct-air-capture industry today, according to the peer-reviewed study covered by Ars Technica.

Read the original report from Ars Technica.