The Immense Scale of Carbon Capture

The World’s Biggest Vacuum

Direct air carbon capture, such as the process developed by Carbon Engineering, pulls CO2 directly from atmospheric air. It is an interesting concept. Such systems could be located anywhere in the world, presumably in lower-cost, remote locations for economical reasons. Unfortunately, they do have some major challenges as well. The CO2 portion in the air, while very high compared to historical levels and significant for the climate, is quite small. In 2019, the average was 408.9 parts-per-million. No carbon capture technology is expected to be 100% efficient, nor would it be good if it were. A massive scale, fully efficient carbon capture system could be bad for the nearby environment by reducing the local CO2 levels too much. For argument’s sake, let’s consider a system which can remove 5% of the CO2 in any air that passes through it. To extract 1 gigaton of CO2, this system would need to process 4.4 quadrillion kg of air. If we assume air pressure at sea level and room temperature, this is roughly 3.6 quadrillion cubic meters of air. If we consider all of the air up to 1 km (3,280 ft.), this volume would cover 14 million square miles. The entirety of North America covers only 9.355 million square miles, so we would need to process significantly more air than covers all of North America up to 3,280 ft. high! Hitting the eventual goal of 10 gigatons per year by 2050 is even harder. The concentration will increase by then, which modifies this calculation, but at current levels this would require processing all of the air covering 71% of the Earth up to 3,280 ft. every year.

Just Plant Trees, Dummy

Perhaps the simplest approach to this problem is to use nature. Trees and other plant life are Earth’s natural carbon sequestration technology. How hard can it be to plant some trees and walk away? Surely they will grow, processing CO2 and producing oxygen. Many scientists and environmentalists have also pushed for this. Not only does it sequester carbon, reforestation does not pollute and has a variety of other benefits (biodiversity, erosion resistance, drought resistance, etc.) if done properly. The process is truly solar powered. In the words of Jeremy Clarkson, “how hard could it be?”

What About The Ocean?

So far, we have focused on carbon sequestration from the air. The prize also covers technologies or approaches to pull carbon from the oceans. The oceans absorb carbon from the atmosphere to the tune of 34 gigatons of CO2 between 1994–2007. That stat alone shows the immense scale of the task — absorbing more CO2 per year than all of the world’s oceans do.

Closing Thoughts

If nothing else, I hope this story is not discouraging. I hope that thinking about the scale brings out new, fresh ideas. Elon Musk is injecting a massive amount of money into a critically important field. He has a long history of leading real progress on ideas that many think are crazy at the time. Landing a rocket on an autonomous boat is stupid, until it works. One company launching more of its own satellites than the total number currently in orbit is laughable, until they just start doing it. Directly interfacing with the brain is not possible, until it works. Electric vehicles are not practical or profitable, until they are. Digging tunnels is way too expensive and slow, until it’s not. If you asked Bell Labs engineers to make giga-transistors when they were building them by hand in 1947, they would probably start crying. Today, a single Cerebras’ AI chip has 1,200 giga-transistors. I am hoping that the same story will be told of carbon capture technology.



Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store