What is Direct Air Capture?
Direct air capture (DAC) is a technology that uses chemical processes to extract carbon dioxide (CO₂) from the air to fight climate change caused by CO₂ emissions.
A DAC system works by using fans to draw in large quantities of air and passing it over solid sorbent materials that have been designed to attract and hold CO₂ molecules on their surfaces in chemical bonding. Alternatively, liquid solvents are used instead of solid sorbents.
The CO₂ is then extracted from the sorbent material or solvent and either permanently stored underground using various methods, such as mineralisation, or used practically in carbon utilization processes, for example in producing sustainable aviation fuel or in the food and beverage industry.
For more detail on DAC, see: How Does Direct Air Capture Work?
Why Do We Need Direct Air Capture?
The world is heating up
This heating up of the Earth has largely been caused by polluting emissions, with CO₂ being the main culprit.
We have to face the alarming fact that the earth has now reached the1.5-degrees Celsius global warming threshold – a critical benchmark set by the scientific community and ratified by the Paris Agreement in 2015.
This is the temperature that the world’s average surface temperature has increased by since the start of industrialisation, and in early 2024, the EU’s climate service announced that global warming exceeded 1.5 degrees Celsius across an entire year for the first time in 2023.
Carbon dioxide concentration in the air
Currently, we are sitting at 420 parts per million of CO₂ in the air and this figure continues to rise. We need to get back down to 350 ppm and the Intergovernmental Panel on Climate Change estimates that we will need to remove 310 billion tonnes of CO₂ from the atmosphere to curb the effects of climate change – raging wildfires, excessive temperatures, droughts, floods and more – which are threatening our food security, flora and wildlife and our planet’s survival.
We have never seen such an urgent need for intervention and DAC is a way to do this.
Emissions reduction is not enough to reach net-zero
For the world to reach carbon net-zero, CO₂ emissions need to be drastically lowered with interventions like switching to renewable energy.
Although reducing carbon emissions is a fundamental part of tackling climate change, this will not be enough. We must remove the legacy CO₂ that is already in our atmosphere, and technologies such as Direct Air Capture have the potential to make a significant difference. What’s more, the CO₂ captured using DAC can be permanently stored away. (For more, see: Carbon Sequestration as Part of CO₂ Storage Strategies)
Direct Air Capture vs Other Carbon Dioxide Removal Technologies
Direct Air Capture is proving to be effective at removing CO₂ from the air, but there are also other technologies for carbon dioxide removal.
This table compares Direct Air Capture (DAC) with other carbon removal techniques, including point source capture, afforestation, and other methods:
| Technique | Description | Advantages | Disadvantages |
| Direct Air Capture (DAC) | Captures CO₂ directly from the atmosphere using chemical processes | Can be deployed anywhere, addresses diffuse emissions, scalable | High energy requirement, expensive, requires storage or utilisation of captured CO₂ |
| Point Source Capture | Captures CO₂ at the source, such as power plants or industrial facilities, before it is released | More efficient and cost-effective at large emitters, mature technology | Only addresses specific sources, not suitable for diffuse emissions, requires retrofitting |
| Afforestation /Reforestation | Planting new forests (afforestation) or restoring forests (reforestation) to absorb CO₂ through natural photosynthesis | Enhances biodiversity, provides ecosystem services, low technology requirement, community benefits | Requires large land areas, long timescales for significant impact, susceptible to land use changes |
| Soil Carbon Sequestration | Enhances the ability of soils to capture and store carbon through agricultural practices, e.g. biochar | Improves soil health, enhances agricultural productivity, low cost | Variability in effectiveness, requires changes in land management, monitoring challenges |
| Bioenergy with Carbon Capture and Storage (BECCS) | Combines biomass energy production with carbon capture and storage | Potential for negative emissions, produces energy, mature CCS technology | Land and water use for biomass, competition with food production, requires CO₂ storage solutions |
| Ocean Based Carbon Removal | Involves techniques such as ocean fertilisation or alkalinity enhancement to increase CO₂ uptake by oceans | Large potential scale, leverages natural processes, could help mitigate ocean acidification. | Environmental risks, unproven at scale, potential unintended consequences for marine ecosystems |
| Enhanced Weathering | Spreads minerals that naturally react with CO₂ across large areas to accelerate the process of natural weathering | Uses abundant natural materials, can be applied on land or in oceans | Requires large-scale mining and transportation, potential ecological impacts, slow process |
The Challenges Facing Direct Air Capture
Direct Air Capture is not without its challenges. The most pressing of these are the high costs and the considerable energy requirements.
As DAC technology advances, the costs are coming down. Initially, removing carbon dioxide from the air using direct air capture has been around $1000 per tonne of CO₂ but that figure can be brought as low as $100-$200 per tonne with the right technology in place.
Since the process of removing the CO₂ is energy intensive, renewable energy is the preferred source such as geothermal, solar or wind energy. DAC systems can be built in any suitable location (they don’t have to be close to the source of emissions) and therefore they can be set up close to sources of renewable energy.
Furthermore, for DAC to be effective in removing the amount of carbon from the air that is needed to reach net-zero by 2050, it will need to be deployed at scale, which will require dedicated investment and political will.
Conclusion
A recent Intergovernmental Panel on Climate Change (IPCC) report – Climate Change 2022: Mitigation of Climate Change highlights the key role that Direct Air Capture (DAC) will have in limiting warming to 1.5 °C. It estimates that DAC will be required to remove up to 310 billion tonnes of CO2 from the atmosphere between now and 2100. This will require enormous investment into DAC technology.
For Direct Air Capture to be a successful part of the broader strategy to mitigate climate change, it requires innovation, investment and support.
For more: The Advantages of Direct Air Capture