If we could turn it to become a resource, perhaps it will be consumed out, just like the rest of resources we humans discover.
One possibility maybe applying photosynthesis, if we knew how to do it in a practical manner. We know that plants can do it, we know generally how they do it, but still can't replicate it.
With photosynthesis, the CO2 ends up in some form of sugar among other things. Where the hydrogen comes from water, and we want that hydrogen for energy.
Of course, as with anything done by humans, there's a danger of abuse. In such case, we could 'overharvest' the CO2 such that it could starve the plants, leading to oxygen shortage... And that's another doomsday scenario.
All in all, the problems point at the humans, so far Earth tolerates us.
Unfortunately, you can't just magic something from a waste product into a resource, particularly something like CO2, due to the second law of thermodynamics.
Carbon fixation is endothermic. It requires a lot of energy, and very specific conditions. Organic carbon fixers (plants & algae) are by far the most efficient way to turn CO2 into something useful, but they require sunlight, and there's only so much of that to go around.
> Unfortunately, you can't just magic something from a waste product into a resource
That's a semantics game... First thing that comes to mind is manure, turned from literally waste into fertilizser. It may not be a high demand resource, but with a utility nevertheless.
CO2 is used in greenhouse farming to increase produce yield. The CO2 gets turned into vegetables. Unfortunately the CO2 will eventually be released again, after the vegetables are eaten.
The O2 content of the atmosphere is 21%. The CO2 content is 0.04%. If you removed 0.04 percentage points of the O2 from the atmosphere, nobody and nothing would bat an eye.
And photosynthesis, as well as any other capture process from air, has negative feedback. If CO2 content (technically, CO2 partial pressure) goes down, the efficiency of the capture process goes down faster.
A great deal of CO2 is absorbed by oceans, which is a moderating factor, but it has its capacity limit. If we tried to 'harvest' the CO2, the oceans may be a more valuable target. Marine plants process it similarly to land plants.
Sure photosythesis needs external energy to work, no one is suggesting a perpetuum mobile. The question is what valuable (to humans) product could be at the end of the processing chain, and how would this balance with the costs? The next question is how to make the process more efficient to drive the costs down?
If plants' process is the most efficient, perhaps it should be delegated to plants, then the humans need to find ways to supply the supporting elements, like soil, light, water.
Photosynthesis is a very inefficient process. It's efficiency is in the single-digit range. It is only worthwhile because the energy source is free and very abundant. And reforestation is only worthwhile because there are benefits to it besides carbon capture.
If we could turn it to become a resource, perhaps it will be consumed out, just like the rest of resources we humans discover.
One possibility maybe applying photosynthesis, if we knew how to do it in a practical manner. We know that plants can do it, we know generally how they do it, but still can't replicate it.
With photosynthesis, the CO2 ends up in some form of sugar among other things. Where the hydrogen comes from water, and we want that hydrogen for energy.
Of course, as with anything done by humans, there's a danger of abuse. In such case, we could 'overharvest' the CO2 such that it could starve the plants, leading to oxygen shortage... And that's another doomsday scenario.
All in all, the problems point at the humans, so far Earth tolerates us.