[OliverM]

No, not in this case. The article already assumes the existence of a near perfectly-efficient process. It's just looking at the minimum energy needed to remove the carbon dioxide from the atmosphere, according to long-established physical laws, no matter what mechanism is used.

We could definitely work harder at supporting the existing natural mechanisms for removing CO2 from the atmosphere, but it's far, far easier to reduce the amount we're emitting.

[aeternum]

Are we all just ignoring that plants pull CO2 out of the air and produce usable energy in the process?

So clearly it is possible to do more efficiently.

[LinAGKar]

Plants aren't that efficient, there's just a lot of them. You could cover the requisite 764 GW with about 3000 km^2 of solar cells (assuming 250 W/m^2). That's a bit over the land area of Luxembourg. Minuscule compared to the amount of area on Earth taken up by plants, and sunlight that falls on those plants.