This is pretty fast. From memory regrowing tropical forests can fix 20 tonnes of carbon per hectare per year. Most of these forests are slash-and-burned on a 30 to 50 year cycle that is carbon neutral, but a slash-and-char approach of about 30% of the forests would capture our total carbon output [0]. It would also have the nice side effect of providing local jobs to some of the poorest people in the world.

0. Research I did when I was an academic and never published. I really should get around to finishing it.