Depends on what you want to do with it?
Are you using it for cooking, blacksmithing or as an amendment to your garden, or to make gunpowder?
Since it keeps basically indefinitely, the ideal amount is probably as much as you can get/make.
I make my own, predominantly to use on the garden at this point, but I could also use it for blacksmithing if needed. I make batches mainly over the Winter and usually end up with 2-3 wheat bags worth ground charcoal.
Having the ability to make charcoal is, I think, more important than having charcoal on hand. This means that I have effectively an infinite amount of charcoal on hand (though in practicality, my charcoal retort has a limited lifespan before it will burn out, I've already gone through two inner drums that have burned up, each batch oxidizes a layer of the steel, thinning it until it finally burns through). My retort is probably about 5 years old now, with dozens of batches through it. It's cheap and easy to make, so re-making it should not be an issue (unless the world has gone to utter shit).
Awesome, This is the response I was looking for. Thank you for sharing your process/knowledge.
Whoa! I'd like to make my own. Could you post some information about how you do it? I think I know the basics but how do you efficiently cut up pieces of appropriate size?
Here's a post I put up a while ago detailing my process: https://poal.co/s/DIY/627390
My source wood is just small branches that fall off trees in my wood lot. I have about 2 acres of Blue Gum trees that are used for fire wood. This provides me with as much wood for charcoal making as I would ever need.
The key to making it is it really needs to be dry. So, I fill the retort, then leave it for a while to dry out thoroughly before lighting it. If it's at all damp, it won't burn well (as the heat is sucked out to evaporate the moisture), and you'll end up with partial pyrolyzation. As for wood size, I generally use branches that are up to the thickness of my arm. I cut them to the full length of my inner drum, and they will pyrolyze fine. You can go smaller, as small as you want, I often pack in offcuts from woodworking to fill up the gaps. That depends on what you want as the final product though. If you're after lump charcoal for smithing or cooking, go with larger branches. I wouldn't go much bigger than ~3" diameter though, otherwise the center might not pyrolyze fully
Here's a pic of a more recent batch that shows the size of the wood I'm using: https://pic8.co/sh/IhGJVP.jpg
(post is archived)