When CO2 is pumped underground, the high pressure makes carbonic acid in any moisture which reacts with calcium to make calcium carbonate. In the ocean, marine

When CO2 is pumped underground, the high pressure makes carbonic acid in any moisture which reacts with calcium to make calcium carbonate. In the ocean, marine life catalyze this reaction to make skeletons, shells, and coral. In shallow bodies of water, the organic material gets mixed in and packed under this lime and sand, and becomes oil and gas. In swamps, plant material gets packed under itself until it becomes coal, and yes, some of it escapes as gas. On dry land carbon fixation is very complicated with many life forms, mostly insects which have skeletons too, but actually the big carbon fixer is fire. There isn’t enough oxygen in a massive fire to oxidize all of the carbon, so you end up with reactions that create large amounts of carbon charcoal and water vapor. Charcoal is biologically useless, so it is fixed, but the minerals in the ash are great fertilizer. Life on earth has been doing this for about 3 billion years now, regardless of us, because the earth is constantly burping up huge amounts of carbon in volcanic eruptions (in addition to great mineral fertilizer). Could we do it better? Maybe, but probably not. I think if you look into any of the new technologies for this, the total carbon cost of production and operation is far far greater than the amount sequestered. I doubt it will ever reach significantly greater carbon:carbon efficiency than nature. There may be something to gain by speeding up the natural processes, but almost certainly more by simply reducing negative interference.