Don't Hold Your Breath for Large Negative Emissions
Energy doesn't for capture doesn't have to come from the electric grid. How about the sun and photosynthesis or geological processes.
I’m particularly confused by this statement:
“A typical coal power plant emits a tonne of CO₂ for every 1,000 kWh of electricity it generates. Meanwhile, we learned that the energy needed to recapture 1 tonne of CO₂ from the air is at least 1,400 kWh. This means that recapturing the emissions of a coal power plant takes more energy than the coal plant produces!”
As you state in the following section, the emissions from the power plant flue gas has concentrated CO2. So, how can you say that recapturing the emissions of a coal plant takes more energy than it produces?
You are comparing the energy to capture CO2 from air with the energy produced by a power plant. What is the energy needed to capture CO2 from flue gas? Instead of the 1400kWh to capture CO2 from air, your number should be closer to 300kWh to capture CO2 from flue gas, leaving a 700net kWh energy from a coal plant.
Thanks for writing this. Having a physics background this was always my skeptical take on carbon capture. I mean you can always do it, just realize it will take more energy (greater cost) than avoiding the release. Still, if you hypothesize an clean-energy abundant future, it may very well be worth considering. At the moment it does not make sense; if you can put a dollar towards clean energy put it there and not direct air capture.