I don't understand your question. GP proposed to filter out O2 by burning carbon. This will create a CO2-rich gas, perhaps at about 30% (depends of the density

I don't understand your question. GP proposed to filter out O2 by burning carbon. This will create a CO2-rich gas, perhaps at about 30% (depends of the density of CO2 compared to O2). GP didn't mean that we deplete oxygen in the athmosphere, but that this is an intermediate step inside the CO2 scrubbing apparatus. Perhaps that's why you got downvotes. The burnt carbon will be gained back by the Gallium process, however this might not work out anyway because the process needs to be very efficient in filtering out CO2, as someone else already pointed out. In my opinion the idea of burning hydrogen seems a lot better: https://news.ycombinator.com/item?id=29994000 https://news.ycombinator.com/item?id=29994000