Small Farm Scale Biochar Projects

We are planning our first attempts at making biochar on the farm to use to improve the soils and crop yields.

Most of the simple means of production that I have found online either produce a very small quantity per batch or require large pits, with an associated danger of a person or animal falling through the soil layer and being severely burned. Also, the fires typically seem like they have to burn for an extended period.

I have a long row of pines that I need to take down as they are starting to shade the kitchen garden near the house, and would like to make biochar from them in the spring or summer.

I read that some make biochar by taking a 55 gallon steel drum, making air inlet holes in the side up about a 1/3 of the barrel height from the bottom, then installing a grate just above the air holes. As the wood above the grate burns, the smaller pieces drop through the grate into the bottom of the barrel where there is little or no oxygen to complete combustion.

My current thoughts are to enlarge this design vertically. First have a steel barrel that has a clamp on lid sitting on the bottom (without the lid). Then stack a second barrel on top of the first. The second barrel would have no top or bottm. It would have short sections of angle iron welded on the inside at the bottom that project about 6" out the bottom to help it nest on top of the bottom barrel. It would have a ring of air holes close to the bottom and a grate of 1/2" steel rods just above the air holes.The entire top barrel would be filled with wood and ignited from the bottom through the air holes. The smaller charred pieces would drop through filling the bottom barrel. Addition wood could be added at the top until the bottom barrel was filled. Then the top barrel would be removed and the lid installed on the bottom barrel.

For utilizing leaves, plant litter, etc. we are thinking about building a device like the one at the link below:

http://www.arti-india.org/content/view/80/52/

I am also looking into Top Lit Updraft Kilns:

http://thinkingglobalactinglocal.com/biochar-workshop-may-9-2009.html

Farm scale biochar making:

http://thinkingglobalactinglocal.com/making-some-biochar/farm-scale.html

Double barrel biochar retort:

http://www.puffergas.com/historic/rules/rules.html

Mac