Delaware Battery-Style CO2 Capture Halves Energy Use

Researchers at the University of Delaware say they have found a way to pull carbon dioxide out of the air using a device built like a rechargeable battery, running on electricity at room temperature. The university says the method uses “about 50% less energy than conventional systems”, which rely on heat.

The university described the work on 26 October in a UDaily article. The underlying results appear in a peer-reviewed paper in Nature Energy, written with RepAir, an Israeli company that licenses the technology and is scaling it up. The work is still at the pilot stage, and its most ambitious cost goal is a projection.

How the device works

Direct air capture means taking carbon dioxide from ordinary air, where it makes up a tiny fraction of the gas. Yushan Yan, who leads the university’s Center for Clean Hydrogen, compares it to sugar dissolved in water. “Imagine adding a teaspoon of sugar to a gallon of water,” he said. “The sugar dissolves readily, even without stirring, but recovering that tiny amount of sugar from the water is much harder.”

According to the university, most current systems use heat to release the captured gas, which costs a lot of energy. The Delaware design uses electricity instead. A nickel hydroxide electrode, the same chemistry found in some rechargeable batteries, captures carbon dioxide on one side of the device and releases it as a purified stream on the other. When one electrode is spent, a second takes over while the first recharges. The device also uses a hydroxide exchange membrane developed at the university and commercialised by Versogen, a company based on its campus.

Yan says the battery chemistry was chosen on purpose because it already has supply chains and factories behind it. “We want to do innovative work but, even more, we want to commercialize technologies that we can see used in the world today,” he said.

What the tests show so far

The paper reports two separate tests. A small laboratory cell, 25 square centimetres in size, ran for 5,000 hours, more than half a year, to test durability. A larger stack of nine cells of 300 square centimetres each then ran for 48 hours. In that test, the authors say, it used energy equivalent to 0.83 megawatt-hours per tonne of carbon dioxide captured, and it met the 300-pascal limit on air resistance that direct air capture systems need.

The university’s article presents these results slightly differently. It says RepAir ran a pilot-scale device in Israel for “more than 5,000 hours”. In the paper, the 5,000-hour figure belongs to the small lab cell, and the pilot-scale stack’s reported test lasted two days. That gap matters, because long-term durability at full size is one of the hardest things to prove in carbon capture.

The cost claim also needs care. The field has long aimed for $100 per tonne of carbon dioxide removed, and James Buchen, the paper’s first author and a doctoral candidate, said: “This technology brings those numbers within reach.” The paper itself presents only “a pathway” below $100 per tonne, based on how fast energy technologies usually get cheaper as they scale. That is a forecast. No cost per tonne achieved today is reported in either source.

There is also a commercial interest to note. The paper declares that Yan is the founder and chief executive of Versogen and a co-founder of RepAir, and four of the authors work for RepAir. The research was funded by the US Department of Energy’s National Energy Technology Laboratory and the US Army Research Laboratory, according to the paper.

None of this makes the result weak. Halving the energy demand of direct air capture would be a meaningful step, and the paper is peer-reviewed. But the long-run, full-size evidence is still to come.

Where it might be used

Buchen says direct air capture is meant for emissions that are hard to stop at source. He named agriculture and construction, including fertiliser and concrete, as two industries where it could help, and said it “can effectively address emissions from distributed sources”. The captured gas could be stored or sold, for example to the drinks industry, according to the university.

Large single emitters are a different problem, often tackled by capturing carbon at the chimney. In the UK, Veolia is supplying capture units for the first waste carbon capture plant at Protos. Other labs are chasing lower energy costs too: one team recently reported a carbon membrane as thin as 2 nanometres that sieves carbon dioxide in lab tests. For more climate and health technology, see TSN’s Tech for Good weekly round-up.