I had a small old woodstove in my step-van and lived comfortably through a Colorado winter. I kept an eye on ventilation and installed it with a heat shield and air space and all that. Made a nice slow cooker and water heater and was oh, so homey.
If there is a next time I would like to try building a small double-cylinder packed sawdust stove that I ran across online recently. Silly me, I forgot to save the page, but if I can track down the design I'll post it.
But here's the gist of it:
The inner cylinder has a small hole in the bottom and sits a bit above the bottom of the outer cylinder and also isn't as tall. Sawdust is hard packed into the inner cylinder around a middle tube (like an old shock absorber) which is then carefully twisted out, leaving a center well. At the bottom of the outer cylinder is a small air intake box with a damper. A lighting tube goes from there to the hole in the bottom of the inner well.
Lit material is shoved into the lighting tube, the sawdust (dry) ignites and slow burns for several hours. The heat goes up the center, hits the lid, goes back down the inner walls of the outer cylinder and comes back up to exit through the chimney, placed midway up the outer cylinder. The chimney has a lower moisture drain and cleanout.
A smaller lid with a small hole in the center can be fashioned for the top of the inner cylinder to blast all the heat to the bottom of the top lid if cooking is desired, then removed for ambient heating.
If built/vented properly for use in a van and used safely, this might be a low-cost indoor heating/cooking appliance, but I make no claims; just sharing something I found interesting.