The problem is the somewhat low atmospheric CO2 concentration; this is why all the "lets just pollute now and remove the CO2 from the atmosphere with some futuristic tech!" approaches are also kinda doomed, because even if you had some workable process that did not cause excessive costs by itself (like this one possibly), you still need to process millions of cubic meters of air, every year, just to compensate for a single (!!) car.
The problem is the somewhat low atmospheric CO2 concentration; this is why all the "lets just pollute now and remove the CO2 from the atmosphere with some futuristic tech!" approaches are also kinda doomed, because even if you had some workable process that did not cause excessive costs by itself (like this one possibly), you still need to process millions of cubic meters of air, every year, just to compensate for a single (!!) car.