Wednesday, March 19, 2014

Terra Preta - Actually Burning Something in the TLUD

There's not much point in building a TLUD unless you actually use it to make biochar, so I'm going to do a quick rundown of the process. 

If you search online for information about TLUDs and making biochar, you'll find all kinds of people saying that you have to carefully pack the material in the barrel to get the most efficient result.  Since I'm not in the business of  'obsessive-compulsive biochar manufacturing', I don't see the need for being that finicky, so I tend to just throw some smaller pieces in the bottom third or so (pack it down a little with a sledge hammer or ax if you have any finicky tendencies).  With the small pieces on the bottom, I think that the process goes a little quicker because the heat from the top will burn through the smaller pieces a little quicker at the end.

After filling the bottom part,  I just fill up the rest of the barrel with a good mix of whatever material I'm using on that day.  

Once the barrel is a little bit below being more or less full, I throw in a couple of empty feed bags (if you don't have any empty feed bags laying around, you'll have to figure out something else, a decent sized pile of dry straw or grass works great).  Throw some nice dry, small kindling type of sticks on top of the bags and you're almost ready to fire it up.

Usually it's a simple matter of  striking a match and setting the bag on fire to get the process started, the draft from the fire seems to start pulling air in from the bottom pretty quick.

Once the kindling on top of the bag starts to burn, the chimney goes on the barrel and the flames should start intensifying because the heat will cause gases to start volatilizing out of the wood and the flames from those burning gases will start traveling up the chimney, and in a few minutes should be coming out of the top of the chimney.

Here you can see the sticks I put the barrel on (bricks and 2x4's also work).  If you use sticks or 2x4's, they'll start to burn when the fire has burned it's way to the bottom of the barrel, letting you know it's time to put the lid on and cover up the bottom of the barrel with dirt to smother the fire.

If you look real close at this picture you can see the fire through a hole in the chimney, at this point there is almost a roar to the fire (it's hard to imagine until you actually hear it).

That simple little hole is an important part of the whole TLUD, it's designed to let me stick one of the tines from a pitchfork into it so I can maneuver the chimney off and on the barrel without having it crash to the ground or burn my hands.  The concrete blocks are on there because the wind was blowing like a hurricane on this day and the chimney was rocking back and forth in the wind (I wouldn't usually burn it when it was that windy but it had drizzled rain all night and everything was soaking wet).

It's harder than you think to catch an elusive flame poking it's head out of the top of a chimney, and it looks smokier than it really is in this picture, but that's the best picture I could get.

About an hour into the process when  the sticks under the barrel have started burning, it's time to remove the chimney, put the top on, throw a couple of concrete blocks on the lid to keep it tight, spray the outside of the barrel down with water to cool everything down a little, and cover up the bottom of the barrel with enough dirt to smother the fire. 

That's basically it, the next day you can dump out your biochar and start the next batch of biochar. 

Next time, I'll show some of the finished biochar, and give you an idea of what I do with it.


  1. Very nice! I'm not OCD, either, so some of the youtube videos made be a bit hesitant. It's nice to see your process and hear about the results.

    Setting the barrel on sticks to see when it is done is a nice detail. Also the chimney-hoisting hole.

    1. It's amazing to me how often someone takes something that's relatively simple to do and then they somehow manage to over complicate the whole process.

      The barrel on sticks and hole in the chimney ideas came to me while I was watching the TLUD burn when I first started using it. Watching a TLUD burn, listening to it roar, and letting your mind wander is a little like a supercharged campfire gazing experience.

  2. I can't wait to see what your bio char looks like. I have a picture in my head but I'm guessing it will be different.

    1. The bio char coming out of a TLUD is a little different than the typical charcoal you get from a open fire or the lump charcoal you might use to grill or smoke.

      It has an almost shiny appearance and easily shatters into little pieces.