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The Amazing Capture of CO2: What's the Science Behind Direct Air Capture?
As climate change becomes an increasingly serious issue, scientists and engineers are actively looking for ways to reduce carbon dioxide (CO2) emissions. Among them, direct air capture (DAC) is gradually gaining attention. It is a technology that directly extracts CO2 from ambient air using chemical or physical processes. As global carbon reduction efforts intensify, DAC is seen as a "negative emissions technology" (NET), which involves many amazing scientific principles and technical challenges.
The direct air capture process not only removes CO2, but also safely stores it in long-term storage
How Direct Air Capture Works
The workflow of the DAC system can be divided into three main stages: contact stage, capture stage and separation stage. In the contact phase, the DAC system uses large fans to deliver ambient air containing CO2 into the device. Then, in the capture phase, the CO2 is quickly and efficiently combined with a liquid solvent or solid adsorbent. Finally, in the separation phase, the CO2 is removed by an external energy source. , CO2 is separated from the solvent to produce pure CO2 for storage or utilization.
The low-temperature DAC process uses a solid adsorbent, while the high-temperature process utilizes a liquid solvent, which has different properties regarding kinetics and heat transfer.
The current status of DAC
As of 2023, DAC technology is still under development, but several commercial plants are already operating in the United States and Europe. The breadth of its applications makes DAC an attractive area of research, and future innovations could make its operation significantly cheaper. However, the current operating cost of DAC technology exceeds US$1,000 per ton, which prevents it from entering the carbon trading market.
Environmental impacts and challenges
DAC supporters believe it is one of the most important tools in the fight against climate change, however, there are also critics who say that over-reliance on the technology could delay necessary emissions reduction measures and that the large amount of resources required to operate DAC is too large. This may offset the environmental benefits it brings.
A 2020 analysis noted that DAC implementation would require large amounts of materials, which would likely not be enough to capture the 3 billion tonnes of CO2 needed each year.
DAC Application Cases
DAC has a wide range of practical applications, including enhanced oil and gas recovery, synthesis of carbon-neutral fuels and plastics, and beverage carbonation. In these applications, CO2 concentration requirements vary, which affects the cost-effectiveness of DAC.
Future Outlook and Policy Promotion
In order to accelerate the application of DAC, policy incentives are a very important part. The U.S. Department of Energy plans to invest $3.5 billion in several DAC hubs, hoping that they will be able to capture at least 1 million metric tons of CO2 from the atmosphere each year and advance the commercialization of the technology.
The development of DAC technology is not only about technological innovation, but also about how policymakers can create a good environment to promote the maturity of this technology.
Conclusion
DAC’s exploration is still ongoing. Can we find more effective ways to address the climate crisis through the joint efforts of technology and policy?
