When CO2 is stored underground, it includes oxygen atoms. What is the impact of taking all that oxygen out of the atmosphere?
I am not expert in this field, but I have two thoughts on the matter. First, there is much more oxygen in the atmosphere than carbon dioxide. The amount of CO2 that needs to be removed from the environment, while it may be an enormous amount of substance, actually represents a small fraction of a percent of the atmosphere. Meanwhile, the atmosphere is about 20% oxygen, so that sequestering that CO2 will have much less effect on the proportion of oxygen than it will on the amount of carbon dioxide.
Second, the oxygen in that CO2 is already bonded in the molecules, so it is not oxygen we can breathe anyway. We can't and we wouldn't ever want to eliminate all the CO2 in the atmosphere. That would bring on other disasters such as the stopping of photosynthesis. The object of carbon sequestration is to try to balance CO2 levels against our consumption of fossil fuels. If there is a threat from the loss of oxygen in the atmosphere, (I don't think there is.) the culprit is the combustion of fuel for our energy.
