1Direct Air Capture
Direct air capture (DAC) refers to technologies designed for removing excess CO2 from the atmosphere and storing it safely deep underground or using it in a wide variety of products. DAC is different from carbon capture and storage (CCS), which captures emissions at a point source like a smokestack.
How DAC works
- Air is drawn in through a fan into an absorbent filter –– located inside a collector.
- The filter includes a CO2-reactive liquid solvent or solid sorbent which traps the carbon dioxide particles.
- When the filter is full the CO2 is recovered by a process that uses heat, an air pressure differential, or a chemical displacement to separate and purify the CO2.
DAC development is evolving rapidly today in various form factors, filtering technologies, energy efficiency, and total capacity. Although costly today, DAC holds great potential in the decades ahead as a climate restoration solution for its durability, financeability, scalability, and equity when thoughtfully developed and further deployed.
Durability
After CO2 is removed from the air through DAC it can be utilized in a growing number of ways, which determines its durability. Highly durable uses of CO2 include 1) pumping it into underground rock formations where it binds with the rock, e.g., basalt, to be stored for centuries, and 2) transforming CO2 into synthetic limestone aggregate used to form low-embodied concrete; the second most consumed material on earth after water.
Financeability
Like solar and wind energy costs, which decreased significantly over time, DAC costs are expected to follow a similar pattern. DAC deployment costs will fall as a result of learning-by-doing, which gains efficiencies and lowers costs with each technology iteration, design improvement, and supporting governmental policy. In recent years, DAC plants have increased in number and scale, while investments in DAC from both the public and private sectors have continued to rise.
Scalability
One of the key constraints in scaling DAC has been its high energy requirements. Locating DAC facilities next to excess energy sources from waste heat streams, e.g., power generators, or renewable wind and solar can help curtail DAC’s energy footprint. Simultaneously, both private investment and publicly funded R&D are ramping up to reduce DAC’s energy needs through innovations that can scale its deployment and capacity for CO2 removal.
Equity
DAC can be implemented equitably — when project developers work hand-in-hand with stakeholders in local and at-risk communities to ensure they are aware of the potential benefits, burdens, tradeoffs, and safeguards needed to protect against unforeseen circumstances or unjust outcomes. DAC’s equitable deployment can be advanced by prioritizing projects that benefit these communities through job creation, reducing air pollutants, or allocating a portion of the profits to support the community.
