Easy kiln/retort ideas

Hi all.

I've seen twice now cast iron bathtubs being given away in my area. Also have seen the info on basically making biochar in a trench. THEN I saw a blog post about using a cast iron tub as fire pit.

So I'm here to ask can I make biochar in a cast iron tub? I'm talking no modifications. The price of a plasma cutter is just out of my range.

But I've got these terrible weed trees that i need to get rid of. They won't make hugelkulture material because they're liable to sprout again if I bury them. And I can't count on the city to clear them. I just want to make the best use of all this waste and brush.

Thank you for any thoughts.

I think it will work.
I suspect the ceramic lining will shatter dramatically,  and after that,  you will be good to go.
Quenching should be a snap.
Those things can be heavy,so be careful with your back, etc.

If you wanted to, you could build a really cool/weird chimney/top for your bathtub.  It could funnel the heat straight up and burn more efficiently.  I just went down to the local restore and bought a tube for $1 and drilled and screwed one together for mine. It's a 55 gallon drum.  This is the video that got me to do it:



John S
PDX OR

I know a few people who are using bathubs as simple open trough kilns. They work pretty well. The enamel does shatter and go away, leaving a cast iron shell that is still fit for purpose. Just be careful of the ceramic shards in the interim, as they are a pain (literally) to deal with in crushed char.

NZ Lifestyle Block magazine did some feature articles last month on biochar production. One of them was about me and my volcano.

Another one was my mate Ben in the South Island with his kontiki, and that one has a sidebar on bathtubs. I'll put up a link to this one when they make it available online.