Direct air capture (DAC) is a technology that removes CO2 emissions directly from ambient air. However, a new analysis by the Australian maths-as-a-service company Keynumbers points that DAC might be to some extent an inefficient exercise.
The calculations show that the emissions contained in the energy that the DAC technology needs to operate are close to the CO2 emissions it captures. In 2020, the world emitted 32 billion tons of CO2 as a result of using 462 exajoules (EJ) of energy from fossil fuels.
If DAC is used to capture that amount of CO2, it would need 448 exajoules of energy. The number doesn’t include the energy that would be required to transport and store the captured CO2. To put that number into perspective, 448EJ is the equivalent of 124,444TWh which is more than five times the annual global electricity consumption in 2020.
“The world would need just as much energy to clean up the energy it made a mess with in the first place…Not quite what the circular economy had in mind,” said Keynumbers founder John Poljak.
According to the direct air carbon capture company Carbon Engineering, the technology will require 8.8GJ energy per ton of captured CO2, instead of the 14GJ-per-ton number used in the analysis calculations. Having this lower number in mind, the world would need just 284EJ (78,888 TWh) per year to capture the global annual CO2 emissions.
The carbon capture investments are also extensive. The largest DAC facility Orca in Iceland recently started operations and is due to capture 4,000 tons of CO2 directly from the air every year. The plant costs $10m-15m which theoretically points that the world would need eight million such installations to capture the world’s carbon footprint.
That would cost a staggering $80 – $120 trillion. However, since the Orca direct air carbon capture plant is just a pilot project, economies of scale would drive the costs down with time.
Even though the world is not going to use only direct air capture for CO2 removal, the findings from the analysis are raising the question of its efficiency in terms of energy usage. It seems like a massive technology breakthrough would be needed to reduce the DAC energy consumption and make the effort worthwhile.