gani et se wrote:I'm sorry, I have no links to John Miedema's system. One reason I like his setup is that he is using char and wood chips to fuel a flame that is fed into a retort. Some of the mobile units in existence use propane. He also is mechanizing fuel feed. The char and chips produce a flame that is fed through a flexible pipe which is inserted into another unit that is producing char and byproducts. He estimates that he is producing enough heat to run 3 chambers, but as this is a prototype, only one is being utilized.
That sounds like the hornito retort. Here it is in action:
And an image:
There's enough surplus gas produced to fire several retorts, but I think you could do more with it, like run an engine or something else.
R Scott wrote:Anybody find a good system for making char out of sawdust on a homestead/small business scale? Every system I have seen for sawdust is either REALLY small (like a handful per batch) or REALLY complicated huge industrial process.
The problem with sawdust is that it insulates well, so in a retort, the center won't get charred. I think I read somewhere where the heat can penetrate 3-4 inches in sawdust. So, they usually do it in tubes 8" in diameter, or in a continuous feed (the industrial method) that has an auger that pushes the sawdust through a tube being heated. I was thinking that you could do a rotating barrel retort for sawdust. That might work, kinda like a concrete mixer with a fire underneath.
the pit/cone kiln method is different, because you are burning the material directly, not in a retort, so it should work better. TLUDs work, too, but usually you need a fan to push the air through the sawdust.
Rice hulls represent similar problems as sawdust, and typically, they char them using mounds:
It's similar to the pit/cone kiln method. You start a fire and then cover it with rice hulls, let it burn through, then add more, until you run out of material, and then you quench it.
If I only want to make a very small amount of biochar (to use in potting soil since none of the commercial amendments are available here), can I just throw water on a fire when the wood is fairly burned up? Or spread the fire out so it dies? Or is real biochar only made by cutting off the oxygen?
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
Thanks Abe and Daniel. Those give me more angles to think about. A tumbler/rotisserie, never thought of that.
The insulation issue is tough, plus the fact it blocks gas flow.
My dream is to get to a gasifier than can run on sawdust and be "detuned" to produce more char as needed.
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You know you can always put tin cans full of what you want to char in your 55 gal TLUD drum and retrieve them at the end of the burn. I find that those tins that Christmas cookies come in work really well. Punch a few holes in them so they can outgas during the burn and you can make your own willow charcoal for drawing. Have you seen the prices for willow charcoal? Char one little tin full of willow sticks and that one little container will bring in more money that the rest of the biochar in the drum.
Even better are those big 3 or 4 gallon metal drums that they sell ridiculously overpriced specialty popcorn in. Another christmass treat for the charers.
And Rebecca, I am no expert here but yeah - if you just rake out a fire and poor water on it, or put a couple shovel fulls of earth on a fire you're trying to put out you'll end up with black char. I have been experimenting the last couple months making potting soil with it and its going really well. I have some really healthy looking squash starting to pop up Courtesy of fellow permie Deb
Rebecca Norman wrote:If I only want to make a very small amount of biochar (to use in potting soil since none of the commercial amendments are available here), can I just throw water on a fire when the wood is fairly burned up? Or spread the fire out so it dies? Or is real biochar only made by cutting off the oxygen?
I'm new to this biochar notion but I believe that char is char by whatever method you make it. Starving it of oxygen lets you get a lot more char per unit weight of wood burned, but you can get a fair bit in a regular open-air fire.
I've got a jungle of early-succession thorny trees on my property -- honey locusts and osage orange. As my energy levels allow -- all I have is hand tools -- I have been "savannah-ifying" them by removing the lower branches. That's left me with a bunch of really hostile brush piles, consisting of almost nothing but thorns. I live in a climate where proper hugels need to be buried, and these woods are both bad for hugel anyway, being very slow to decay. So I do burn some of these piles when conditions are right.
Trouble is, conditions are almost *never* right for safe burning around here -- I need still air and high moisture in the underbrush, which almost never happens. But last week it did -- there was a slight drizzle that had been going for hours, and not a breath of wind. So I burned one of my piles. I needed some accelerant to get the pile burning, and as soon as the big flames died down the fire started to go out because of the continuing rain. So I just raked the hot coals apart and let the rain hit it. Went back the next morning when the ashes were cold and filled two five-gallon buckets with the resulting char. It's not enough for amending acreages, but I put five gallons straight into the mixing bin I use to prepare soil for my container gardening. The other five gallons is soaking in a bucket with some dog poop; I'll mix that deep into the soil of some of my larger planters after it's had a chance to ferment and mellow a bit.