[BariumBlue]

Quick math, it takes 10+ times more energy to scrub and then store carbon from the air, then you get by burning natgas for the same amount of CO2. (1 ton of LNG produces 100 KWh and 2.76 tons CO2, and the thermodynamic minimum energy required to extract CO2 from ambient air is about 250 kWh/ton CO2, but apparently realistically closer to 1,200 kWh / ton.)

It'd make way more sense to first focus on decarbonizing our energy grid, before starting to spend 10+x more energy to recapture and push it back underground.

[hedora]

We’ve already emitted so much CO2 that we have to capture a lot of what is currently in the atmosphere. Also, decarbonizing the grid with solar, wind, tides, nuclear, and even geothermal is going to involve generating massive amounts of waste electricity.

On top of that, some energy generation technologies (like solar) are ramping faster than Moore’s law used to. That means that non-peak energy production will no longer be scarce, so thermodynamic efficiency is a second-order effect.

In all likelihood, the most economic path forward probably involves simultaneously drawing down CO2 and also generating 5-10% of the energy we use from fossil fuels, 90-95% from renewables, and an additional 10-100% on carbon capture.

[notatoad]

obviously not putting the carbon in the air in the first place is the best solution, and carbon removal has the real potential to take away electricity that could be used for other productive purposes.

but clean energy isn't entirely fungible, and if you've got a context where it's abundant then it can make sense to use it for carbon removal. we just need to be careful that the carbon removal projects are only getting built in places where the energy would otherwise be wasted.

[cperciva]

While I agree about the thermodynamic argument -- you can't extract CO2 from the atmosphere without using significantly more energy than you released by burning fossil fuels -- there's an argument to be made that not all kWh are equal. If you can extract CO2 from the atmosphere close to the equator at noon on a sunny day, you're going to be able to do that pretty cheaply.

[Thorrez]

>thermodynamic minimum energy required to extract CO2 from ambient air is about 250 kWh/ton CO2

How is Heirloom doing it? Are they spending 250 kWh/ton for the extraction? They're reacting it with limestone, and it doesn't sound like that's taking a lot of energy.

[jgilias]

They need to initially (and then repeatedly) heat the limestone in order to release and capture the CO2 in it. This way they get some really CO2 hungry sand that binds it from the air.

I’d expect it’s the rock baking part that takes the most energy.