This innovative technology allows us to remove carbon dioxide directly from the air using liquid solvents and solid adsorbents in large machines. The carbon dioxide in the air passing through the machines reacts with these chemicals, called "capture agents", and is removed from the air. The carbon dioxide must then be separated from the capture agents so that these chemicals can be reused and the carbon dioxide stored.

Liquid solvents

Among the main liquid solvents is potassium hydroxide (KOH), which, when reacted with carbon dioxide, generates potassium carbonate (K2CO3). In order for the potassium hydroxide to be reused in another operation, the carbon dioxide must be separated from the compound produced (K2CO3). One way to do this is by using calcium hydroxide (Ca(OH)2), which, when reacted with potassium carbonate, produces calcium carbonate (CaCO3, limestone). Finally, CaCO3 can be decomposed to produce a pure carbon dioxide stream that can be stored or used in certain industries. The great advantage of liquid solvents (potassium hydroxide and calcium hydroxide) is that they can be reused over and over again. However, it takes a lot of energy to remove carbon dioxide from potassium and calcium carbonates, so liquid solvents are more expensive than solid adsorbents.

How does liquid solvent DAC work?. ClimateScience. (n.d.). Direct Air Capture: Using Machines to Suck CO₂ From the Atmosphere. https://climatescience.org/advanced-direct-air-capture

Solid adsorbents

Solid adsorbents are filters that are made of a material to which CO2 readily adheres. Once these filters are saturated with carbon dioxide from the air entering the collector via a fan, the temperature of the collector is increased to 80–100 °C. This process allows us to release the carbon dioxide in a concentrated stream that can be stored or used. The advantage of solid adsorbents is that they require less energy than liquid solvents; however, they produce waste as they can eventually wear out, unlike liquid solvents that can be used over and over again.

The Solid Adsorbent Process. ClimateScience. (n.d.). Direct Air Capture: Using Machines to Suck CO₂ From the Atmosphere. https://climatescience.org/advanced-direct-air-capture

Direct Air Capture (DAC) is an innovative technology that could help us remove carbon dioxide from the atmosphere and reduce air pollution. It is an expensive technology, but it can bring great benefits to the planet.

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