What are direct air capture plants, and how do they pull CO2 from thin air?

The answer

Direct air capture (DAC) plants use chemical processes to extract CO₂ from ambient air where it exists at just 420 parts per million. Climeworks, the Swiss market leader, uses solid sorbent filters that chemically bind CO₂ when air is drawn through them. When heated to 80–100°C (using geothermal energy in Iceland), the sorbent releases concentrated CO₂, which is then dissolved in water and injected 700 meters underground, where it mineralizes into basalt rock within two years - permanently removing it from the carbon cycle. Carbon Engineering (acquired by Occidental Petroleum for $1.1 billion) uses a liquid solvent system in its STRATOS plant in Texas, targeting 500,000 tons annually by 2025. A 2024 DOE-funded project by Heirloom Carbon uses limestone-based passive DAC that's potentially cheaper, at under $100 per ton, by leveraging natural mineral carbonation accelerated through process engineering.