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biochar

Questions About Making Biochar

pollinator

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Location: Zone 10a, Australia

posted 10 years ago

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It is raining the third day in a row and I am spinning ideas around......
I am reading about biochar.
I think of building a drum biochar oven, it sounds easy.
I have some questions, how dry must the stuff be? How small must I cut it? Can I use twigs with the leaves on it?
I would like to build something with cooking option too.

It seems that the biochar is an easy way to use the twigs I really can easily get hold of (only ask some gardeners and you have heaps).
I investigate this after having asked how much it cost to hire a chipper for a day ($185).

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R Scott

pollinator

Posts: 4182

Location: Tennessee 7b

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posted 10 years ago

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Dryer the better. You have to cook out all the water with outside fuel before you can start to gasify and self sustain the burn.

Twigs work, leaves and all, if dry. Maximum size depends on the size of the retort and ability to maintain heat. A 55 gallon drum can do 2x4's scrap, or anything you can prune with a loppers, much bigger and it won't char all the way through before you lose heat.

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Angelika Maier

pollinator

Posts: 1475

Location: Zone 10a, Australia

posted 10 years ago

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Thanks that means that I pile the stuff up for several months before burning?
And what do you think of the drum burners? However, we are not allowed open fires (bonfires) because of the bushfire danger.

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R Scott

pollinator

Posts: 4182

Location: Tennessee 7b

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posted 10 years ago

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Drum burners that use the woodgas to keep the fire going are fairly efficient if insulated or wrapped properly. It all depends on the scale you want to do. Going bigger than a 55 gallon drum gets expensive fast.

I don't know your climate for how long it would take to dry down trimmings. I find more value in leaves and new wood as compost material, but I have a shredder to speed up composting.

Patrick Mann

Posts: 310

Location: Seattle, WA, USA

posted 10 years ago

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Check out this video on a simple pit burn method for making biochar
https://turkeysong.wordpress.com/2014/10/04/simple-efficient-cheap-flexible-trench-biochar-method-video/

http://thirteenvegetables.wordpress.com

Bryant RedHawk

gardener

Posts: 6829

Location: Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5

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The safest, cheepest method I've found is to build a small J tunnel rocket stove that feeds a 55 gal drum that fits over the riser.
If you make the drum a bell, with the outflow at the bottom of the barrel, then you install the chimney pipe to end at least three feet above the barrel (bell) top.
Build a small rack (can be made of bricks or even cinder blocks) to hold the wood upright, fill as tight as you can for maximum char production, there will still be room for airflow with round wood.
If you are using split wood, just make sure there are channels for air flow between the splits.
fire up the rocket stove and the heat will flow all around and through the wood to become char, one full burn is usually enough if you are using split wood or branches and twigs.
The top of the barrel also functions as a cook top when done this way. Make sure the wood doesn't reach all the way to the barrel top or it will stall the rocket.

There are good threads on this site and at pdf rocket stove build directions
Using the pdf, you can build a smaller char builder such as using a cheep 12 quart and up stock pot with steel lid not glass. This is easier and doesn't need as much rocket stove knowledge or outlay of money.

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Angelika Maier

pollinator

Posts: 1475

Location: Zone 10a, Australia

posted 10 years ago

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A rocket stove seems to be a bit complicated. I will not use split wood, need that for heating. I will have to use the leftover bits. The climate here is unpredictable, mountains climate.
How much can I produce in 55 gal drum? HOw much do I need per m2 anyway?
I do no want to use an open fire pit because I will have the fire service here very soon.

Medicinal herbs, kitchen herbs, perennial edibles and berries: https://mountainherbs.net/ grown in the Blue Mountains, Australia

Bryant RedHawk

gardener

Posts: 6829

Location: Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5

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posted 10 years ago

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I use small branches for most all my biochar, I spread it at a rate of 4 cups per sq.ft. then dig it in. That's the only time we till soil, to get the biochar down where it does the most good.
I have a test plot of 2' by10' that I just spread it on the surface then used a broadfork, that test area was a bust.
The gardens where it was dug in, are very healthy one year after the introduction, and we won't have to ever do it again, which is one of the up sides.
The microorganism counts are now up at least 10 fold from before the introduction and the mycoremediation is really going strong.
We did not have any water retention issues before the introduction of the biochar and still don't have any water issues.

a short term rocket can be built just using bricks with mud used as the mortar, they only take an hour to put together and that is far safer than an open pit fire since the flames are contained.
a 55 gal drum will make enough biochar (in one loading) to properly do a 4x8 bed. I don't currently have biochar everywhere, just in the garden beds. I may never have it everywhere.

Ci Shepard

Posts: 16

Location: Vancouver Island, BC

posted 10 years ago

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Can someone please link me to an easy metal drum biochar oven build instruction?

Bryant RedHawk

gardener

Posts: 6829

Location: Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5

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posted 10 years ago

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list of biochar oven videos These should get you going.

Bryant RedHawk

gardener

Posts: 6829

Location: Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5

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posted 10 years ago

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The simplest method is to take your sticks and twigs, cut to a length that will fit on aluminum foil, wrap tightly (two layers or three layers), poke two small holes (one at each end), then set this package in your charcoal grill and fire it up. The wood inside the aluminum foil package will char nicely. Depending on your grill's size, you could make a fair amount at one firing of the grill or you can make some biochar while you cook supper. It takes about one hour using this method. Note: This works best if you have a grill with a lid, that way you are giving it the oven effect.

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