Biochar Mini-Kiln Success | The Survival Gardener

I got two #10 cans and made a little biochar retort with the method shared in this post.

My six-year-old son and I then packed it full of wood chips and sweetgum seed pods. Then we started up a fire in the fireplace, put in some logs, then put the retort in with them for the night.

In the morning, the fire had burned out so I pulled out the retort. To my surprise, it was really light. Disappointed, I assumed the interior had burned away into ash.

Yet when I opened it, I found it was half-full of beautiful, perfect biochar.

Since almost everything had burned out of them except for the carbon, the char left was quite light.

The sweetgum pods looked amazing.

This is really a clever way to make small-scale, perfect char.

Our next experiment will be to make artist’s vine charcoal for one of my daughters so she can draw with it. We cut a bunch of pieces of wild muscadine vine and put them into a smaller retort made from two “family size” tomato soup cans.

If you regularly run a wood stove, a cooking fire or a fireplace, this is a fun way to make biochar for free. The charcoal is higher-quality than you can get by doing a burn outside and quenching it, plus you can char materials that would just melt away in an open fire.

I’d like to try this with some pecan shells.

As LiveOnWhatYouGrow commented on my YouTube post about our success with his method:

“Because I’ve been making biochar for so long this way I’ve forgotten that leaves, grass, cardboard, paper, pinecones, hair, and other things like that, really can’t be made into biochar in an open fire because they’ll completely turn to ash! In the retort, everything inside turns to char because, at temperatures of over 1200°F, all the volatile compounds in the organic matter expand and turn to gas, but with no oxygen, they can’t burn. So, at those temperatures, all the gasses are driven out of the end hole and the seams where they combine with oxygen and burn outside the retort leaving only carbon inside! The best part is that I get to heat my house for free here in Connecticut while making at least 600lbs (275kg) of biochar each year! I used to make it outside in a pit, but then I had to pay for fuel to heat my house!”

Pretty cool, and a great project to do with kids.

Once you have your char, just soak it in something mineral-rich to “charge” it, then add it to your gardens.