- Direct Air Capture (DAC) is an advanced climate mitigation technology that involves the mechanical extraction of carbon dioxide (CO₂) directly from the ambient atmosphere. Unlike traditional carbon capture methods that target emissions from point sources (like power plants or factories), DAC is designed to reduce historical and dispersed emissions by removing CO₂ already present in the air, making it a potentially essential tool for achieving net-zero or even net-negative carbon emissions.
- DAC systems use chemical sorbents or physical filters to capture the relatively low concentrations of CO₂ in the atmosphere (about 0.04%). Typically, air is drawn into a processing unit by large fans, where it passes through filters or materials that selectively bind CO₂. The captured CO₂ is then released by applying heat or changing pressure in a regeneration step, which allows the sorbents to be reused. The purified CO₂ can either be permanently stored underground via geological sequestration or utilized in products like synthetic fuels, carbonated beverages, or building materials.
- There are two main technological approaches in DAC:
- Liquid Solvent-based Systems – These use alkaline chemical solutions (e.g., potassium hydroxide) that react with CO₂ to form carbonates. The carbonates are then processed to release pure CO₂ and regenerate the sorbent.
- Solid Sorbent-based Systems – These use solid materials (like amine-coated filters or resins) that adsorb CO₂ from the air. Heat or vacuum is applied to release the captured CO₂ for storage or reuse.
- While DAC is scientifically feasible and technically proven, it is energy-intensive and currently expensive compared to other carbon removal methods like reforestation or soil carbon sequestration. The main challenges lie in scaling up, lowering costs, and ensuring the use of renewable or low-carbon energy to power the process, so that DAC doesn’t contribute more emissions than it removes.
- Despite these challenges, DAC has notable advantages. It offers location flexibility, as facilities can be built anywhere with access to clean energy and storage infrastructure. DAC is also uniquely suited to offset unavoidable emissions from hard-to-abate sectors such as aviation, shipping, and certain industrial processes. Moreover, it plays a crucial role in carbon dioxide removal (CDR) portfolios proposed by international climate assessments like those from the IPCC (Intergovernmental Panel on Climate Change).
- Major companies in the DAC field include Climeworks, Carbon Engineering, and Global Thermostat, all of which have developed pilot or commercial-scale facilities. For example, Climeworks’ plant in Iceland, in partnership with the CarbFix project, captures atmospheric CO₂ and stores it in basalt rock formations, where it mineralizes into solid stone within a few years.
