38,000,000,000/4000 = 9,500,000 plants needed to get to net zero, just for the the carbon we are currently putting out, to say nothing of all the carbon currently causing warming...
Reasonable if you assume that progress of this technology has already plateaued. I'm pretty sure we could be putting a lot more money behind this and we would see substantial improvements to efficiency (i.e. $/kg/year).
We need every tool we can get to fight this thing.
A tree absorbs around 20kg of carbon dioxide a year while growing. To sequester 38 Gigatons you'd need to plant and cut down and bury around 10^12 trees each year, give or take an order of magnitude or two.