Once again, the acrid tang of innumeracy wafts from from a BBC report. The claim in the article is that the technology may remove CO₂ from the atmosphere for less than US$ 100 per tonne. Let’s assume they manage to achieve that goal. Extracting CO₂ from the ambient air is just the input to a scheme for Direct Air Capture (DAC). Swiss company Climeworks sells subscriptions to virtue-signaling corporations with more money than sense such as Microsoft to remove 10,000 tonnes of CO₂ over ten years, or 1000 tonnes per year, in a subscription at an estimated price of around US$ 1100 per tonne. Now, it is estimated that the technology Climeworks is using for capture costs around US$ 350/tonne, so if you could reduce that to US$ 100 and all of the savings are passed on to the “subscriber”, that only reduces the total cost to US$ 850, including processing, transportation, and sequestration. Let’s be generous and assume they can get it down to US$ 500 per tonne, all expenses included.
Now, between 2020 and 2021, global carbon dioxide emissions increased by around 1.5 billion tonnes. So, suppose we want to offset all of that increase (the second derivative of atmospheric carbon content), stabilising the emissions of carbon dioxide at their 2020 level via DCA? Well, that will cost 1.5 billion tonnes times US$ 500/tonne, or US$ 750 billion. Now, that doesn’t sound too bad, when everything seems to cost a trillion here and a trillion there. But there’s a bit more to it than that. According to the International Energy Agency, Direct Air Capture requires, depending on the technology used, between 6 and 10 gigajoules of energy per tonne of CO₂ removed from the atmosphere. So, the 1.5 billion tonnes of increase will require (assuming the lower figure of 6 Gj/t) 9 exajoules per year. Global energy consumption is around 550 exajoules per year, so this would add 1.6% to energy consumption. Where is that energy going to come from? 9 exajoules per year amounts to 285 gigawatts of base load generation power, which at 2 gigawatts each (much higher than the actual average which is around 0.58 gigawatts), would require 143 dedicated nuclear power stations just to power carbon capture.
But this is just to offset the increase in emissions in one year. To reach “net zero”, you’d have to take out all of the CO₂ emitted every year. That’s about 33 billion tonnes per year, so now we have an annual cost of US$ 16.5 trillion per year, or around 70% of total GDP of the United States, and an energy requirement of 198 exajoules, or 6274 gigawatts from 3137 nuclear power plants, which is around seven times the total number of nuclear power plants in operation worldwide today.
And that’s just to offset the yearly increase in atmospheric CO₂. You say you’d like to reduce it…?
