Critics argue that DAC is energy and cost-intensive, with limited outcomes compared to resources invested.
United States President Joe Biden has allocated up to $1.2 billion in funding for the establishment of two carbon capture facilities in Texas and Louisiana. These will utilise the contentious Direct Air Capture (DAC) technology, which numerous experts assert is both energy and cost-intensive, yielding comparatively limited outcomes compared to resources invested.
Let’s understand the argument against and in support of DAC.
What is direct air capture?
Direct Air Capture (DAC) is a technology that removes carbon dioxide (CO₂) from the atmosphere.
Using high-powered fans, the air is drawn into a processing facility where the CO₂ is separated through a series of chemical reactions, explains 1PointFive, one of the two American companies engaged in the Biden administration project.
Then the CO₂ is either permanently stored in underground reservoirs through secure geologic sequestration, or is used to make new products such as building materials and low-carbon fuels, it adds.
Why is the removal of carbon so crucial for mitigating global warming?
Carbon, mainly as carbon dioxide (CO2) and methane (CH4), worsens global warming by intensifying the greenhouse effect.
The greenhouse effect, like a blanket, allows sunlight to warm the Earth’s surface. As the surface emits heat as infrared radiation, these gases absorb and re-emit some heat, trapping it in the atmosphere. Though this is vital for Earth’s temperature, human activities like burning fossil fuels and deforestation have increased CO2 levels, strengthening the greenhouse effect and raising temperatures.
Carbon dioxide is a relatively stable gas with a long atmospheric lifetime.
Challenges and criticism of capturing CO2 directly from the atmosphere?
Capturing CO2 from the air is more energy intensive – and, therefore, more expensive – than capturing it from a point source, a report from International Energy Agency (IEA) says.
This is because CO2 in the atmosphere is much more dilute than, for example, in the flue gas of a power station or a cement plant.
Two technological approaches are currently being used to capture CO2 from the air: solid and liquid DAC. Solid DAC (S-DAC) is based on solid adsorbents operating at ambient to low pressure (i.e. under a vacuum) and medium temperature (80-120 °C). Liquid DAC (L-DAC) relies on an aqueous basic solution (such as potassium hydroxide), which releases the captured CO2 through a series of units operating at high temperatures (between 300 °C and 900 °C).
A diverse portfolio of technologies exist for S-DAC, differing in energy intensity, operating temperature, and therefore cost.(IEA)
What is the current scenario of direct air capture technologies?
According to IEA, 27 DAC plants have been commissioned to date worldwide, capturing almost 0.01 Mt CO2/year. Plans for at least 130 DAC facilities are now at various stages of development.
“If all were to advance (even those only at the concept stage), DAC deployment would reach the level required in 2030 under the Net Zero Emissions by 2050 (NZE) Scenario, or around 75 MtCO2/year,” the report adds.
What is the way ahead?
According to experts, advancements in utilising CO2, such as synthetic fuels, hold the potential to lower expenses and establish a market for DAC. Initiatives have already commenced to create synthetic aviation fuels by capturing CO2 from the air and combining it with hydrogen. Additionally, research in efficient energy sources will make the process less energy-intensive.