Charcoal brooding heaters

So in some parts of Africa, clay or metal charcoal burners are used to keep young chick's warm.
They are valued because they can burn for upto 12 hours, and they are "clean burning" enough to use indoors.
Some of them have reflectors, some don't.
The metal ones can be as small as a cook pot or as big as a 55 gallon drum.

Does anyone here use them?

Could these be good greenhouse heaters?

When I was a kid, my father would bank the fire in a chick brooder stove with the biggest lumps of coal that would fit through the door. This kept the chicks warm all night but was slow burning so it wasn't a major fire hazard. That dry, warm heat was amazing (spiced with the peep-peep-peep of fuzzy chicks -- good memories)!

That would have worked well in a greenhouse as well. I imagine a charcoal barrel heater would also. It would need to have a larger volume given the lower BTU value of the fuel, and a system to ensure the air flow wasn't choked off by the charcoal fines and ash.

The problem with wood charcoal is that a lot of the heat value has already been lost in process of making it. (That's why adding mass is a hot topic here.)

A possible experiment: I've noticed partially burned wood chunks that have been completely cooled, with a layer of char on the outside and what I assume is a partially torrified wood core, burn much slower than regular firewood -- even in a regular fire. I wonder if that might be a reasonably efficient homemade fuel for banking a greenhouse burner. This fuel could be deliberately made as part of a biochar burn, cooled and stored.

That sounds like quite the sense memory!
As I continue to look into this idea, I've even found people using charcoal heat for incubating eggs.
The steadiness and the cleanliness seems to be why charcoal heat is favored in these applications.

I'm facinated because it's yet another use for charcoal, and a way to be self sufficient in brooding heat, with minimal infrastructure.

Solo smokeless firepits are basically a gasifire woodstove or tlud.
They sell a heat deflector to go over the firepit,  because the double walled construction cools the sides and sends almost all the heat strait up.
I think a homemade version could be useful as a brooder, especially if it were used to heat a low slung mass that had an insulated top, like a Kotatsu...

I just checked,Kotatsu table chicken brooder picks up no relavant hits on Google!