The Walden Effect: Farming, simple living, permaculture, and invention.

How to make biochar

The internet is chock full of articles glowing about biochar's potential, but I seldom find any useful, hands on information.  The Abingdon Biochar presentation we attended delved into the nitty gritty.

Today's video highlights methods you can use to make biochar on any scale.  I was especially intrigued by the idea of modifying a rocket stove to produce biochar while cooking your dinner.

Our homemade chicken waterer is a simple DIY project that requires an hour or less to produce clean water for your flock.

This post is part of our Biochar Videos lunchtime series.  Read all of the entries:

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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The production of carbon fiber is made by pyrolysis too. A synthetic fiber (usualy polyacrylonitril) is heated to up to 3000K in an oxygen-free atmosphere. This shakes all hydrogen atoms loose leaving only pure carbon. There seem to be two important factors in this process;

  • high temperature
  • lack of oxygen

The second means using a closed container to contain biochar. When heating organic materials which are mainly carbohydrates, volatiles will be released (at the very least all the hydrogen you've cooking off). You'd want to capture those to help fuel the process.

A fluidized bed reactor would probably be the most efficient to char organics (they've been used successfully for energy generation from coal and biomatter) but they're probably out of reach for most people.

So take two concentric drums like the video suggested. Put the dry material (boilding off water takes lots of energy; not efficient) to be charred in the inner drum and put a lid on it. This drum goes in the outer drum where wood is burned to heat everything. The lid of the inner drum should contain a pipe to lead the escaping volatiles through a check valve and to a burner under the inner drum.

The check valve is important since you don't want oxygen getting into the inner drum but you want the volatiles to escape without pressuse build-up (think explosions :-) )

Comment by Roland_Smith Wed Sep 1 15:01:51 2010
Thanks for breaking it down so simply --- I'd been meaning to do some research on pyrolysis and see if there was more to the process than I'd gotten out of the talk. Mark thought high heat was essential from something Rory Maguire said, and it sounds like he's right. Thanks!
Comment by anna Wed Sep 1 15:48:37 2010

The following page will give you an idea of how much fuel it takes to make charcoal (which is more or less the came as biochar I think, but made from wood instead of other plant material :-) ), pretty much using the process I described; Making Charcoal.

You'll be burning about ½ as much wood as you're putting in to make charcoal. And that is with using the volatiles from the wood itself.

I'm surprised that steel barrel can withstand the heat. I wonder how long they'll last?

Comment by Roland_Smith Wed Sep 1 19:07:37 2010

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