[tackem (OP)]

We can freeze carbon dioxide.
Can we not produce a propulsion system to send it into space like a home grown comet?

[Bored chemist]

It costs roughly as much to put something in space as its weight in gold.

[Colin2B]

For every molecule of CO2 you send into space you send 1 atom of carbon and 2 of oxygen, I’d rather we find a way of splitting off the carbon and keeping the oxygen.

[tackem (OP)]

The line between atmosphere and space is about 100km.
We have artillery that can fire projectiles further that that so if we had shells of frozen CO2 we can fire them into space at a reasonable cost.
We could alternatively use urea which sequesters CO2 during production (only to give it back when used as fertiliser).

[Halc]

The line between atmosphere and space is about 100km.
We have artillery that can fire projectiles further that that so if we had shells of frozen CO2 we can fire them into space at a reasonable cost.

Those projectiles 1) don't go 100 km straight up, and 2) always hit the ground.

To get something away from Earth, you need to exit the atmosphere at escape velocity, which is over 11 km/sec after passing through the entire atmosphere. Anything less and it just comes right back.
Assuming you had some unfathomable technology that would prevent the projectile from burning up during that, it would still require vastly more energy (more carbon dug up from the ground) than the amount of carbon ejected into space, so it would have negative benefit.