A Cool (Temperature) Take on Direct Air Carbon Capture December 11, 2023
Introduction:
(Eurekalert) Lehigh University engineering researchers working with a Pennsylvania-based technology company have recently entered the second phase in the development of a novel ion-exchange method to capture carbon dioxide that could potentially run on waste heat produced by industry.
The method pairs a filter (more specifically, a capture sorbent, a material that absorbs CO2 gas) with an electrochemical cell that breaks down sodium sulfate into sodium hydroxide and sulfuric acid solutions. These weak base and weak acid solutions work together to capture and subsequently purify the captured CO2.
Eventually, the technology will be packaged into a unit about the size of a shipping container.
“Air flows through the filter, which captures the CO2,” says Arup SenGupta, a professor of both chemical and biomolecular engineering and civil and environmental engineering and lead researcher on the project. “When the filter capacity is exhausted, the conversion process initiated by the electrochemical cell produces pure CO2 that you can then pressurize and put in underground storage, or liquify and sell on the market.”
Additionally, he says, the sodium hydroxide and sulfuric acid recombine in the process to form sodium sulfate. “So you can keep using the salt to sequester CO2, in theory, forever,” he says.
Direct Air Capture: An Expensive, Dangerous Distraction from Real Climate Solutions by Kurt Zenz House, Josh Goldman, Charles F. Harvey
December 15, 2023
Introduction:
(Bulletin of Atomic Scientists) This month elites from 198 nations gathered in the fossil-fuel-rich United Arab Emirates for the 28th annual Conference of the Parties to the United Nations Framework Agreement on Climate Change. Near the top of the agenda is the deployment of technologies to remove carbon dioxide, the principal greenhouse gas causing global warming, from the atmosphere. The week before the conference started, The Economist published an approximately 10,000-word special report on the topic, and the Financial Times reported that direct air capture of carbon dioxide is “grabbing investors attention.”
All year, the zeitgeist has been building toward technologies that separate carbon dioxide from air, referred to as direct air capture (DAC). In September, the United States Department of Energy awarded Occidental Petroleum a $600 million grant to build a DAC machine. As scientists and entrepreneurs who’ve dedicated our careers to help solve global warming, you might expect us to be happy.
We are not.
The reason is simple: Separating carbon dioxide from air, while technically straightforward, is outrageously expensive. In fighting climate change, the obvious question should always be: How can we avoid the most carbon dioxide per dollar invested?
Conclusion:
Unlike other climate technologies, the only way to make air capture a business is with oil production and perpetual giant subsidies. Misallocating resources to air capture makes the planet hotter. The only winners are the recipients of the subsidies and the builders of the boondoggles.
The sustainably powered, electrochemical reduction of carbon dioxide (CO2) into useful chemicals and feedstock could help to mitigate greenhouse gas emissions, allowing industries to reuse released CO2 in beneficial ways. Most of the strategies for realizing this introduced so far, however, have notable limitations, including a poor stability over long periods of time.
Researchers at Hong Kong Polytechnic University, University of Oxford and the National Synchrotron Radiation Research Center recently introduced a new membrane-electrode-assembly system that could facilitate the stable electrocatalytic reduction of CO2.
Notably, their proposed system, which was first introduced in a paper published in Nature Energy, is fed by pure water (H2O) and thus does not rely on alkali-metal electrolyte.
In a corner of Kelsey Hatzell's lab sits a small jar filled with a material that has an ability far beyond what its nondescript appearance would suggest: a way to capture and release carbon dioxide from the atmosphere by simply changing the surrounding humidity.
The material could slash the energy costs associated with so-called direct air capture systems, which conventionally rely on energy-intensive temperature or pressure shifts to switch between carbon capture and release. By instead relying on humidity, the material could yield energy efficiency improvements over five times above current technologies. The researchers report their findings in Environmental Science & Technology Letters.
