Biochar-making Cookstove, Top Lit - Not a TLUD #cookstove

Kevin McLean

Have any of you tried this and can you provide direction? 

I put additional holes in the bottom of a terra cotta pot.  I filled the pot with hardwood chips to 2" below the top and lit the top of the fuel.  Once the fire was strong, I added a handful of fuel every few minutes.  The level of the fuel remained the same throughout, about 2" from the top.  I quenched with water after 30 minutes. 

The fire burned very clean.  The result was about 50% biochar (by volume, compared to the total fuel used).  There was just a little unburnt wood that had not turned to char.

What seems to be happening is the heat from the fire pyrolyses the fuel below.  The pyrolysis gasses rise to the fire and ignite.  More photos and videos are in this folderThis video is particularly interesting.  Note the flame on the left side curling over the trapped smoke.

This method can probably be used with agricultural waste such as corn cobs and stalks.  There are many ways to place a cookpot above the fire.  We don't have a good way to turn down the heat, yet.

Ron Larson and I have been trying to design low-cost cookstoves that make biochar.  If we are successful, the Catholic Church can probably train smallholder farmers in Africa to make and use biochar to improve crop production.

If you have done something like this, I hope you will share your experiences.


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