The amount of energy required by the direct capture of carbon in the air shows that it is a useless exercise

Capturing CO2 Emissions using direct air capture (DAC) technology require nearly as much energy as that contained in the fossil fuels that produced the carbon dioxide in the first place, according to a new analysis.

In 2020, the world used 462 exajoules (EJ) of energy from fossil fuels, resulting in 32 billion tons of CO2 emissions. Capturing that carbon dioxide via DAC, which removes greenhouse gas from the air, would require 448EJ, according to calculations by Australian math-as-a-service company Keynumbers.

That 448EJ is the equivalent of 124,444TWh, more than five times the world’s annual electricity consumption in 2020 (23,177TWh, according to Enerdata). And that doesn’t even include the energy that would be required to later transport and store the captured CO.2.

“The world would need the same amount of energy to clean up the energy it messed with in the first place,” said Keynumbers founder John Poljak. “It’s not exactly what the circular economy had in mind.”

Generally speaking, DAC technology works by using giant fans to draw in air, with the CO2 (about 0.4% air content) adheres to chemicals known as absorbents. When the sorbent is saturated, it is heated to 80-100 ° C to release the captured carbon dioxide.

The world’s largest DAC facility, Climeworks’ Orca plant, which costs between $ 10 and $ 15 million, opened in Iceland last week and is expected to capture 4,000 tons of carbon dioxide from the air each year, the equivalent to the emissions of about 870 cars. Captured CO2 It is then mixed with water and injected into a basalt rock 1 km underground, where it slowly turns into a solid carbonate mineral over two years.

So, theoretically, it would take eight million such plants to capture the world’s annual carbon emissions, at a cost of $ 80 billion-120 billion.

Of course, Orca is just a pilot project and costs would inevitably fall with economies of scale and technological development.

In fact, Climeworks’ rival, US-based Carbon Engineering, believes it will require 8.8 GJ per tonne of CO captured.2, instead of the 14 GJ per ton figure used in Keynumbers calculations. With this lower number, the world would need just 284EJ (78,888 TWh) per year to capture annual global carbon emissions.

It has also been said that nature – trees, plants, soils and oceans – absorbs about half of the planet’s annual carbon emissions. So in the best case, using current technology, the world would need 142EJ (39,444 TWh) each year, almost twice the world’s annual electricity production, to soak up all of our carbon emissions from the air.

No one is suggesting that the world should capture all of its greenhouse gas emissions using DAC, but the amount of energy required raises questions about whether the technology makes any sense. After all, the world needs to quickly decarbonize its current energy use, not add to the burden required.

And with major oil and gas producers like Chevron and ExxonMobil investing millions of dollars in DAC, rather than investing in clean energy, it’s hard to argue that current direct air capture technology is little more than greenwash, a bad one. excuse to keep emissions high with the promise that they can be removed from the air at a later date.

While economies of scale and efficiency improvements would certainly help, it seems more likely that a massive technological advance will be needed to reduce the energy required by DAC to an acceptable level.

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