If you accept that dumping carbon into the sky is detrimental...
...(and we don't need to bog ourselves down with that controversy, here, do we?) then it really does not matter where it comes from. Carbon in the atmosphere is carbon in the atmosphere.
Now if you want to promote removing carbon from the atmosphere, then maybe you should give a bonus to the guy growing the crop. Hmmm, what an odd idea. Wonder why no one's thought of it...