Direct Air Capture (DAC) is a class of carbon-dioxide-removal technologies that chemically extract CO2 directly from ambient air, rather than from a concentrated flue-gas stream. Captured CO2 is then either permanently stored underground or used as a feedstock, producing measurable negative emissions. DAC is energy-intensive because atmospheric CO2 is highly dilute, so its viability depends on low-carbon energy and durable storage or carbon-market incentives.
- Direct Air Capture extracts carbon dioxide directly from ambient air using chemical sorbents or solvents, producing negative emissions when paired with durable storage. It is a cornerstone of Climate Policy strategies aimed at Net Zero, complementing point-source capture by addressing diffuse and historical emissions.
- Unlike Carbon Offsetting schemes that avoid emissions elsewhere, DAC physically removes CO2 from the atmosphere, but at high energy cost that ties it tightly to Renewable Energy supply and to Carbon Pricing economics.
Overview
- DAC plants pull large volumes of air across a contactor where a chemical agent binds CO2. The agent is then regenerated, releasing concentrated CO2 for compression, transport and storage or utilisation.
- Two dominant approaches exist: solid sorbent systems operating at moderate temperatures with low-grade heat, and liquid solvent systems using aqueous hydroxide solutions regenerated at high temperature.
- Because atmospheric CO2 is roughly 0.04% by volume, DAC must process enormous air throughput, making energy efficiency the central engineering and economic constraint.
- The output of DAC is a quantifiable, verifiable removal that can be credited under rigorous carbon-accounting frameworks, distinguishing it from softer offset claims.
Mechanisms
- Air contacting: fans draw ambient air across a sorbent surface engineered for high CO2 selectivity.
- Capture: amine-functionalised solids or hydroxide liquids chemically bind CO2 from the passing air stream.
- Regeneration: heat, pressure or moisture swing releases the captured CO2 and restores the sorbent for reuse.
- Conditioning and storage: released CO2 is purified, compressed and either injected into deep geological formations or converted to fuels, materials and chemicals.
- Measurement, reporting and verification underpin the credibility of each removed tonne.
Applications
- Permanent geological sequestration to deliver durable negative emissions.
- Supply of climate-neutral CO2 feedstock for synthetic fuels and building materials.
- Corporate net-zero portfolios seeking high-permanence removals beyond avoidance offsets.
- National climate strategies addressing residual and hard-to-abate emissions.