What is Direct Air Capture and how does it work?

This article demystifies Direct Air Capture technology by explaining what it is, how it works (diagram), viability, limitations and greenwashing. DAC is viable, but not a golden bullet solution.

This article demystifies Direct Air Capture technology by explaining what it is, how it works (diagram), viability, limitations and greenwashing. We conclude that DAC is indeed viable; DAC is essential to to support a transition to net zero. It is not however a golden bullet that will 'solve climate change'.

What is DAC technology? Direct air capture (DAC) technology is a carbon capture & storage solutoin (CCS) that involves the capture of carbon dioxide directly from the atmosphere with industrial equiptment. DAC is expected to be a key technology in the future of net zero energy systems, whereby emissions of CO2 are equal to the amount of CO2 sequestered and stored. It is one of few technological options for removing CO2 directly from the atmosphere.

How does direct air capture work?

This Carbon Capture process uses large fans which draw in air and filter out CO2 molecules, like an atrificial tree! Polluted air goes in, fresh air comes out. CO2 is chemically bound to filters as air passes through the machine, it is later collected from the filter and passed on to vairous storage options.

Direct Air Capture Diagram

Direct Air Capture Diagram (Copyright - Climeworks)

Some companies providing DAC:

How is carbon Stored?

Typically, the carbon dioxide is then collected and pumped deep into the earth where it stays indefinitely. These storage places are known as geological reservoirs. Carbfix specialises in this form of storage, mixing CO2 with water and pumping it underground. The CO2 then mineralises, turning to stone (image and diagram below). Alternatively, DAC facilities can sell the carbon to other industires, who re-use it to balance their emissions, acheiving 'net-zero'. Coca-cola did this for the CO2 in their soft drink. CarbonCure use this to produce carbon capturing cement! An average high rise building built with their cement stores the equvalent amount of CO2 as a forest of 888 acres captures in a whole year!

Image: Carbfix carbon storage solution

Limitations of Direct Air Capture technology

At scale, DAC has the potential to reduce atmospheric concentrations of carbon dioxide to a significant extent, helping to mitigate harmful effects of climate change. However, DAC technology is still in its early stages of development and is currently expensive, making it difficult to implement on a large scale. As such, further research is needed to make DAC technology more cost-effective and efficient.

Is Direct Air Capture Viable?

Direct air capture is a realistic and viable option, but not a golden bullet solution. DAC should be used to support a transition toward renewables for industries that are difficult to decarbonise.

For the time being, a large DAC facility is able to remove 4,000 tonnes of CO2 per year (Climeworks Orca Facility). In the future this is projected to rise significantly. For example, 1 Point Five, a US based DAC company, is currently building a facility capable of removing 500,000 tonnes of CO2 per year.

Is Direct Air Capture Greenwashing?

Companies can use DAC to accomplish 'greenwashing' if it is used as a scapegoat to expand harmful operations and neglect environmental footprint. DAC, if powered by renewables, is not inherently 'greenwashing', but we must consider how this tool is used. Companeis must reduce their impact on many facets of the environmnet, not just carbon. Furthermore they should source renewable energy and reduce their emissions where possible, using DAC to counter-balance areas that cannot be reduced in order to acheive net-zero.

Conclusion

Climate change is too complex an issue to have a single solution. Direct air capture plays a small but critical role in supporting net-zero transitions, by balancing emissions left over once heavy decarbonisation is acheived. It is not currently scalable to fully decarbonise a sector, and comapnies still need to practice positive environmental action alongside DAC.

Explore the world of carbon capture

Sources

1. Lackner, K. S. (2020). Direct air capture of CO2 with solid sorbents. Science, 367(6482), 1001-1006.

2. Jones, S. (2019). Direct air capture of carbon dioxide. Nature Reviews Chemistry, 3(7), 454-465.

3. Smith, K. (2020). Direct Air Capture of Carbon Dioxide: A Promising Climate Mitigation Technique. Environmental Science & Technology, 54(19), 11861-11864.

4. Schenk, P. M., Keith, D. W., & Lackner, K. S. (2016). Direct air capture of CO2 with chemical looping. Science, 354(6314), 842-844.

5. National Academies of Sciences, Engineering, and Medicine. (2020). Direct Air Capture of Carbon Dioxide: A Technology Assessment. Washington, DC: The National Academies Press.

5. Climeworks