As far as reducing carbon dioxide concentration is concerned, what we ought to do is make things - houses, furniture, ships - out of wood. This will stop (or at least greatly delay) it decaying and its carbon being respired by the decomposing microorganisms.

Or even just grow a lot more of it and then store it somewhere it won't rot. Like shrink-wrapped in plastic, down an empty coal mine.   

Has nobody thought of this?

S