Thursday, December 27, 2012

A Burning Issue...

A completed burner for making biochar
It may just be the next best thing since sliced bread.


Or, if you like something more familiar… charcoal.

It’s what you get when you partially burn wood or other organic matter. Black, crumbly charcoal.

When I dumped the ash buckets today, I sifted and separated the charcoal from the ash with a screen I use for compost. That resulted in a bucket full of charcoal… or, biochar, it sounds more sophisticated.

A couple of years ago, I’d read about biochar being a good soil amendment and was intrigued, but not intrigued enough to actually try making any and using it. About three weeks ago I attended a workshop about biochar, which included construction of a burner to more efficiently make it. That’s when I was really sold on it.

Using a half-inch bit, drill a series of holes in the bottome of the barrel,
approximately 2 inches apart, with a cluster of holes at the center to
facilitate air flow in the center of the burning materials.
This char does not possess any special nutrients, but is porous and full of nooks and crannies that make good homes for all those beneficial fungi and other microorganisms so essential to soil health and plant nutrition. Also, the chemical structure of char (largely carbon) causes it to attract various ions of common plant nutrients, thus retaining soil nutrients long term when they might otherwise escape. The char also retains moisture, making plants growing in it more drought tolerant. And finally, it improves the structure of soil, turning clay into friable earth and sand into fertile fields.

And if that weren’t enough, biochar will save the world.

Cut a hole in the lid into which the stove pipe will fit tightly.
With tin snips, make tabs around the bottom of one lenght of
Or, at least, it might help reduce the release of greenhouse gases, particularly carbon dioxide, by keeping lots of carbon in the soil. If I understand the science correctly, when plants decay or are fully burned down to ash, pretty much all of the carbon in them is oxidized – that is, it links up with oxygen to create carbon dioxide and other greenhouse gases. By partially burning this matter, you prevent up to half of the carbon from being released into the atmosphere. Mixing it with soil sequesters the carbon, locks it up in the soil for centuries. If enough people do this, the theory goes, we can not only halt the increase of carbon dioxide in the atmosphere, but start decreasing it, thus preventing (or at least slowing) warming of the earth’s atmosphere.
...then slip the pipe into the lid and bend back the tabs so the pipe
is secured to the lid. The other two lengths will be added only
when you do a burn.

So, by mixing this char in my soil I can not only get healthier and more nutritious vegetables and fruits, but also save the world from global warming.


All of this theory is intriguing enough, but at the workshop, we heard first hand reports of its miraculous nature from people who have used it.

You can make biochar in a trench in the garden, as demonstrated in this article that appeared in Mother Earth News a few years ago. Or you can make it more efficiently by creating a burner from a 30- (or 50-) gallon steel barrel with a tight-fitting lid, three lengths of 8-inch stove pipe, some ceramic fiber insulation (fiberglass will deteriorate rapidly with the high heat of burning the char), chicken wire, a pair of tin snips and a half-inch drill bit for use on metal.
Wrap the ceramic fiber insulation around the barrel and
secure it with chicken wire.
The burner must be set up on bricks, so that air will flow from the bottom and up through the wood chips or weedy materials packed not too tightly into the barrel. Light the top of the materials with charcoal fluid or some kind of tinder, such as dry grass or newspaper. Put the lid on top and let it burn. In 60 to 90 minutes, the fire will have reached the bottom. You must then extinguish it immediately, before the fire starts back up and burns the charcoal to ash.

Two rows of holes at the lower end of the bottom length of
pipe create a "second burn," which creates a smoke-free burn.
We plan to make one of these, but I am not waiting for that to happen before I get some char. When we clean the stove, especially before it is completely burned out, a lot of chunks are in the ash. They are still burning embers, mostly, but putting all that ash and coals in a metal bucket with a tight lit prevents all of it from burning up (other stuff in the wood burns before the carbon does, then the carbon burns, leaving only ash). I use my compost screen to separate the char and the ash. Just crunch up the charcoal and spread it on the garden.

As a caveat, I read a recent article saying that the European Union has decided that biochar wil not save the world, and that it should not bear the exotic name biochar, but simply be called "plant charcoal." Whatever. The article did not cite particular studies or info as to why they made this decision. However, the testimonials I heard on that chilly Sunday afternoon were enough to convince me that at least it will help my garden grow.

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