First time firing up the TLUD - troubleshooting

Hay howdy -

I recently made a TLUD off the warmheart worldwide plans ( https://youtu.be/YIbGkmt1VdE)  Filled it up with twigs and branches up to 2" in diameter and fired it up on Saturday. OoOoo'd and ahhhhh'd at it's magnificence, as it deserved. Quicker than I thought (about 20-25 minutes firing time) I started seeing fire reflected out the bottom holes so I splashed the bottom of the barrel with some water and got instantaneous sizzle, all the way around. Per the video and other sources, that was the indicator the burn was done! So we doused and dumped.

What was in the bottom 1/5 of the barrel, maybe 2 gallons when all crumbled up, turned into a lovely biochar, the rest ranges from soot-stained to half way to char. The larger chunks (up to 2" diameter, kept them 4-6" long) were barely touched. It's like the fire got pulled to the bottom of the barrel too quick.

I'm not sure what to modify for next time. Does it just need more time, even tho the splash test was indicating it was done? Are there any other indicators of it being done I'm looking for?  Is there a strategy to loading it with material? Anything else I might have missed?

I wasn't expecting total success I know I need to get a feel for it - just not sure what to fiddle with first, timing, loading, material?

Also, i've been wondering if using mulch from tree trimmings, sourced from chipdrop (local tree trimming companies) would work int he TLUD.  Is that too small a material to make into biochar?

Thanks for any thoughts y'all. Enjoy your day.

Based off your report, I would try a taller chimney for more draft to reduce the "fire got pulled to the bottom too quick" effect. I would also sort your fuel so that it's all the same size per batch for a more consistent burn, and if that doesn't work do something like layer the larger fuels toward the top, so that they are fully charred by the time the fire reaches the bottom.

I also base my biochar system on the Warm Heart video.  It was the first system that I saw and could say, "I think I can do that!".  It works really well.  However, I think that splashing on the side as notification of when it is done was one of the weakest parts of their video.

Over time, I realized that I could make a much better predictor of when to douse the fire.  I realized that when the char is all pretty even in the bottom, and the flames are about 5-10 inches (12-25 cm) above the height of the char, that's the best time to finish it.  I literally just came back into the house after burning biochar, my first of the year.  I usually end up with just a few, maybe 3 or 4, pieces that are burned around the outside, but the inside is wood. I break off the char from the outside and store the inside for the next burn.  I figure that's about the right time. If I burn it much further, a lot of the char turns to ash, which is what I don't want.  I have noticed that I get a lot of char this way. Much more than burning just a bit further.  

The one other part of their video that I didn't think worked very well was the highly complicated measuring of the string on top.  I think it's easier just to put the chimney on top, draw around it, and use that as the basis for the cuts.

John S
PDX OR

Fuel consistency is a key factor in success with TLUDs. My personal favourite is stove pellets due to their high energy density.

I use my TLUD stoves, which all have forced air, to cook on and as the heat source for my retorts.