Containers for making biochar inside a wood burning stove?

i admit that i have never used biochar but in terms of producing it, what about a butane gas cylinder, either the ones used for domestic cooking or smaller ones used for camping. the steel is definitely strong enough to last. if its cut  into a large piece maybe 80% of the total volume, the remaining 20% would be used as a top. The larger lower part would have its top bent in to allow the other piece to sit on top in the form of a cap or lid.

Yes, like others have said, biochar is when you burn the wood or other material so that all of the oils, aromas, and volatile compounds are gone and it is just a light, easily crunchable black piece of carbon, which is now usable for microbe hotels.  There is no wood left in it either, so it's not good for barbeques.  

I just use a 55 gallon steel drum I got for free. I made it into a TLUD. I've made 30 or so burns with it. No sign of wear.  

I drench the fire when the tiny flames are just barely above the charcoal, like one or two inches above.  
Very little smoke, great biochar, very little ash.

JohN S
PDX OR

Thank you guys! We own an old heavy duty pressure cooker, like this one, but much older. Bought it used at an antique store, thought we might ahve gotten a bargain, but it's not water tight. Of course, that means it's also NOT air tight. All I have to do now is figure out where to cook it. It's way too tall for our wood stove.

Jennie Little wrote: All I have to do now is figure out where to cook it. It's way too tall for our wood stove.

What would be the ideal dimensions for your stove? Print it up and post at your local bulletin boards{church?} for a trade{this comes from the tale of Ali Baba and the Forty Thieves - fiction is useful}. Specify that it is unrepairable as a pressure cooker. I always make it a point to highlight the dangers or shortcomings up front. I can't shake this particular habit/compulsion/obsession. If you are lucky, you can join the ranks of biochareers very soon. You might even convert the other party. Mention biochar in your notice. If people understand the purpose they might make more effort to rummage through their kitchen. If you run out of fuel, I understand there is a surplus of used clothing in the USA. Make charcloth and offer it to outdoorsmen and women.  I missed the too tall bit. Ask around for anyone handy with an angle grinder. That should do the trick then.