Where to Find Charcoal?

I've already done the herbalist unlock quest, but my poor wolf rolled in some poop and got diarrhea. I haven't found any charcoal at all in explore even though guides place it existing in many of the biomes, including my pack's home. 

Basically just wondering what encounter or anything else has a chance of giving it? Or is it completely RNG?

It's mostly random.

Some herbs are easier to find in some biomes, as you read in the guide, but there's no encounter that gives you surely a certain herb.

If you need charcoal and you have some other herbs, you can exchange 3 other herbs for 1 charcoal in the Exchange section of the herbalist page.

Oh no! I hope your wolf gets better soon. However, you are correct, Charcoal is found in many biomes! The encounter to get it is having your wolf come across some herbs in a biome with those plants and gathering them. The herb you get is unfortunately random; otherwise you could also have your herbalist forage for some herbs and (also) return back with a random herb native to your biome.

Also, yes, you can exchange for herbs at Herbert for 3x your own to a Charcoal!

Oh, thank you both for the information! The tip about exchanging herbs is actually very useful, and I had no idea about it. Managed to get 2 out of the 3 charcoal needed, hopefully I can find another before the end of this day. 

Seriously, thanks so much. :)