Yeah - charcoal is incredible stuff. Nothing organic leaves my property. I burn green & brown waste in a simple kiln made from corrugated iron & then quench it at the end with water.

It's free charcoal & turns the soil a lovely black colour. I can't make enough of the stuff.

My soil doesn't crack that badly but it's rarely bare & full of rocks.

I used to try & rot the branches & cleared trees but they dry out & take forever to break down (a lot of Australian gum trees). The charcoal chunks get smaller & finer over time but don't really break down. I use the bigger chunks to grill with.

If you're going to purposefully grow material to make bio char, I think bamboo is best. It grows fast & the charcoal it produces is very porous & easily crushed.