Direct air capture: hoovering up carbon

Carbon capture does what it says on the tin. it is the process of capturing carbon, usually in the form of carbon dioxide (CO₂), and from here there are several routes, including underground storage and carbon “upcycling” into new chemicals. Direct air capture (DAC) is a relatively new method of carbon capture and storage, and some plants even allow for carbon recycling.

In Iceland, you will find the world’s first large-scale air capture plant, Orca. Running on geothermal energy, the plant captures CO₂ directly from the air. The plant can capture up to four thousand tons of CO₂ a year^[1]; and although costly just now, this growing industry is an extremely promising development in climate change prevention, with nineteen air capture plants operating across the world^[2]. Direct air capture plants like Orca work by using large fans to “suck in” air, which is then reacted with “carbon capturing” chemicals. A Hydroxide solution can do this, as well as solid amine sorbents, which “adsorb” CO₂ (gathering the CO₂ molecules on its surface— not to be confused with “absorbing” into the solid!). The carbon is then isolated and mixed with water. It is then either stored in deep geological formations where it turns to rock, or it can be combined in chemical reactions to make, for example, synthetic fuels.

However, there are issues. These plants are no small feat, financially or energy-wise. The Orca plant is lucky enough to be running on renewables, but this is not the case for all plants. Additionally, it is still unclear if DAC is viable as a long-term solution to climate change, as it is expected to be incredible energy intensive if used on large enough scales. If DAC plants were running on scales large enough to limit global warming to 2℃, by the year 2100 they would be using a quarter of the world’s energy demand in heat and electrical energy^[3] —not to mention additional energy in for the mass-manufacturing of CO₂ adsorbents as well!

Overall, it seems that DAC is certainly a step in the right direction and an interesting use of science and tech. In good sizes, DAC will be a helping hand in slowing climate change but should not be relied upon as our saviour in this climate crisis.

Edited by Liam Butler

^[1] https://climeworks.com/roadmap/orca

^[2] https://www.iea.org/reports/direct-air-capture

^[3] https://www.carbonbrief.org/direct-co2-capture-machines-could-use-quarter-global-energy-in-2100