So, using an Imbert or even an old side draft is just fine for any demo, any plant will run on charcoal.
Char, biochar, charcoal whatever you want to call it is a byproduct of wood gas plants, not the other way around, except in emergency running and , education, so your project is a good one for teaching.
For me its all about the fuel and learning to handle that, and getting a minimally processed fuel to do what I want. So with that in mind, if you want to do a machine that produces fuel, look at the "Laimet screw chipper", open source build that and you got my attention. This is one of the best machine available for fuel wood chunks and has variable spacing on the blade sets for different sizes. https://www.youtube.com/watch?v=2JU5DFSf5Ow The one in this video has a fine cut blade, I am looking for more of a 2" block size for my stuff.
This is or should be one of the machines vital to society, just not too many people know about stuff like this because most people have never had to provide their own fuel.
I cant run this seminar just now, I have too many irons in the fire.
You may have this but its a really good basic book (PDF) on charcoal production and history from the good ol Forest Products Lab in Madison.