Direct Air Capture
Direct Air Capture utilizes large fan-like machines to remove CO₂ directly from the atmosphere. Captured CO₂ can either be stored permanently in rock formations underneath the earth’s surface or reused for other materials.
Introduction
DAC is a permanent, secure, scalable solution–making it exciting addition to carbon removal toolbox. It is often compared to using a giant ‘vacuum cleaner’ to suck Co2 out of the air. While a simplistic explanation, it conveys the ability of this machinery to actually scrub CO2 out of the atmosphere essentially anywhere.
The modular ability of DAC machines, as they do not take up much land, is limited by the energy it requires to operate this machinery. This impressive engineering requires a huge amount of energy which must come from renewable sources to be sustainable, and must be planned carefully to achieve this.
The Process
The three main steps of this engineered carbon removal process are:
Air Capture
Air passes through the huge fans. CO₂ is separated through several chemical reactions or physical interactions.
Air Release
Clean air, with a minor concentration of CO₂, is released back into the atmosphere.
Injection
The captured CO₂ is stored underground in geological reservoirs for thousands of years.
How it works
Fan
Air is introduced into the facility by high-powered fans. These large mechanical engines, composed in series of ten to twelve units in a structure similar to a cooling tower, pull the air in horizontally.
How the capture works? - Step 1
Air passes through a filter that traps CO₂. Two technologies are currently available: either a liquid solvent solution, typically potassium hydroxide, or a solid sorbent. Due to the high affinity between these compounds, carbon dioxide binds to them either chemically or through physical interactions.
How the capture works? - Step 2
CO₂ is concentrated and collected as a gas through temperature increase and pressure reduction. Liquid solutions require additional chemical processes, such as the incorporation of calcium hydroxide. The process recycles and reuses chemicals, filters and solid contactors and returns the clean air back to the atmosphere.
Carbon Storage & Use
The compressed gaseous CO₂ is pumped underground, where it is stored permanently, effectively, and securely. The carbon is securely stored in saline formations or depleted oil and gas wells or turned into carbonate minerals thorugh a mineralization process. Alternatively, the captured CO₂ can be used in to generate green fuels that substitute fossil fuels, but as this does not lead to carbon storage, Klimate does not work with this process.
A permanent, secure, scalable solution
Among the available methods for CO₂ removal, DAC is one of the solutions believed to be scalable at the velocity needed to achieve the emission removals targets by 2050.
DAC has several advantages compared to other methods, especially reduced land and water needs. The main drawback is the huge amount of energy it requires, which will have to be provided from renewable sources.
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DAC could become a key option for climate change mitigation in the next few years. Several studies estimate that the engineered solution could reach gigatonic scale by 2050 (1 Gt CO₂ per year). However, to achieve this target requires further technical and economic development of the already commercially available technology. Moreover, scaling up will result in a significant reduction of costs, leading to Direct Air Capture being economically competitive among the carbon dioxide removal (CDR) methods.
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Environmental and social co-benefits provided by DAC are generally smaller than other CDR technologies. However, directly cleaning the air that we breathe by removing CO₂ from the atmosphere is the main positive impact of Direct Air Capture, improving human health and well-being as well as mitigating climate change.
Besides, CO₂ collected that is not stored underground, can be utilized as feedstock for long-lifetime products, of which building insulation and cement stand out, contributing to carbon removal.
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