Comment by vel0city

But if the CO2 recently came from the atmosphere it's still a net zero impact though.

Like, take 5 units of carbon out of the atmosphere to create the fuel. Burn it and release 5 units of carbon to the atmosphere. What's the net increase again? (-5) + 5 = ?

FWIW I'm not saying these processes actually achieve this in reality. Just pointing out that it could be carbon neutral in the end.