Direct air capture (DAC)
Also known as: DAC, direct air carbon capture, DACCS, direct air capture and storage
Direct air capture (DAC) uses large fans and chemical filters to pull carbon dioxide directly out of ordinary air, so it can be stored permanently underground or used in products.
Unlike capture at a smokestack, it can remove carbon that's already in the atmosphere. While DAC is one of the few true 'negative emissions' technologies, it's still very expensive and tiny in scale compared with the billions of tonnes the world emits.
Direct air capture (DAC), explained at three levels
At home
Imagine a giant air purifier that, instead of removing dust, removes carbon dioxide. Fans pull air through special filters that grab the CO2, which is then stored deep underground.
At work
Companies buy carbon removal credits from DAC projects to offset emissions they can't eliminate, like those from air travel. Because the carbon is stored permanently and measured, these credits are considered high quality, but they're expensive.
At home
CO2 makes up only about 0.04% of air, so DAC machines must process enormous volumes. Solid sorbent systems use filters that capture CO2 and release it when heated; liquid solvent systems use chemical solutions and high-temperature processes.
At work
DAC costs are often estimated at several hundred dollars or more per tonne today, with targets of US$100 to US$200 in the future. It needs abundant clean energy, since powering it with fossil fuels would undercut the benefit. Storage is usually in geological formations, and buyers often pre-purchase removals through advance contracts.
At home
The physics is unforgiving: separating such a dilute gas takes a lot of energy no matter how clever the design. In my opinion, that's why DAC will likely stay a niche tool for the hardest emissions rather than a general solution.
At work
Assess DAC claims by verified net removals after accounting for energy use, construction, and leakage, and by registry and measurement standards. Watch for removals used for enhanced oil recovery, which complicates climate accounting. Government support, such as US DAC hubs and tax credits, has faced political uncertainty, so contract terms should address delivery risk.
Real-world examples
At home
Aisha wanted to offset the emissions from a flight to visit family overseas. She compared cheap forestry offsets with a much pricier DAC removal credit and chose a small DAC purchase, valuing its permanence and measurement.
At work
Jerome manages sustainability at a Canadian tech company with a net-zero pledge. After cutting emissions where possible, the company signed an advance purchase agreement for DAC removals to address residual emissions, with clauses covering delays.
Common confusions
- DAC can clean up the world's emissions at current scale. — Global DAC capacity is tiny, measured in thousands of tonnes compared with billions emitted each year.
- DAC is the same as carbon capture at power plants. — Point-source CCS captures concentrated CO2 at smokestacks. DAC pulls dilute CO2 from ambient air.
- DAC removal is cheap. — It's currently among the most expensive ways to deal with a tonne of CO2.
For analysts
DAC credits are expensive but rigorous, so they make sense for the last few percent of emissions. I'd push for real reductions first, then buy removals with clear delivery dates, measurement, and refund terms.
History & origin
Scientists, including Klaus Lackner, explored capturing CO2 from air in the late 1990s. Swiss company Climeworks opened its first commercial plant in 2017 and its Orca facility in Iceland in 2021, designed for about 4,000 tonnes a year. Canada's Carbon Engineering, founded by David Keith, piloted its technology in Squamish, B.C., and was acquired by Occidental in 2023 for about US$1.1 billion. Climeworks' Mammoth plant began capturing CO2 in Iceland in 2024, with capacity designed for up to 36,000 tonnes a year, though reports later suggested real removals were far below that. Occidental's Stratos project in Texas, designed for 500,000 tonnes a year, has been in commissioning. In my view, DAC deserves investment as a long-term tool, but it shouldn't be treated as permission to keep emitting today.