Shortly after I first heard about biochar I knew I had to at least experiment with making some. Unfortunately I do not have an easy access to big barrels, metalworking skills or a place to store a big kiln. Instead I went small and made myself a home-made TLUD kiln from an old (thoroughly cleaned) paint can and some soup cans. After a little experimentation with getting proper air circulation, I got some good results. Here are a few pictures.
The "construction" is really simple. I used a single 1 gallon paint can and 3 soup cans. One soup can I remove the top lid. The other two soup cans I removed both the tops and bottoms with a can opener. On the paint can I used a drill with a 3/8 inch bit to drill about 10 holes into the bottom sides. I then drilled a hole in middle of the lid and used a tin snip to cut away 4 petals. These petals are pried back and used to help hold a soup can in place. I then fit one soup can over the petals and rested the last soup can on top of the 1st. I experimented with air holes in the soup can chimney, but I think I drilled at least a dozen 1/4 inch holes around the base of the chimney and a few on the chimney 2nd level. The two soup cans that make up the chimney are simply resting one atop the other and they are held in place by the petals I peeled back. I did not want to make anything too rigidly constructed as I have heard of these bursting under the right (or wrong) conditions.
To start a batch, I split a piece of hickory (good hardwood, but other wood will probably work just fine) into pieces about the diameter of my thumb and as long as the interior soup can. I really pack that soup can full and then turn it upside down (the wood is tight enough that it stays in place) and place in the paint can. Then I put more hickory in the paint can around the soup can and fill with as much wood as I can get in. I try to keep a piece of charcoal from my last batch to use as a starter, but this is not strictly necessary as long as there is some fine kindling on the top. After I have packed in as much wood and kindling as I can, I light the top of the kindling and put the lid on, then stack the chimney, sit back and wait. My batches took about 90 minutes. WARNING, this gets VERY hot! Make certain you do this far away from anything heat sensitive/flammable.
I had to try this twice before I got it right. At first I got nothing but smoke from my chimney--and LOTS of it. After I fiddled and drilled some additional air holes (really, you need to figure out the exact fuel/air ratio yourself. I really don't know what wood you will burn, nor the moisture content. Mine was fairly dry hickory) it burned COMPLETELY smoke free.
Really it is a simple process, you just need to experiment a little.
I really hope this helps. If you want any more suggestions, feel free to ask. And when you make your own batch, please do send pictures!!
Some places need to be wild
Location: Suburbs Salt Lake City, Utah 6a 24 in rain 58 in snow