3-drum Biochar Retort – Construction and User Manual

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Product Description


The 3-drum Biochar Retort was developed following extensive field trials with the TransPortable kiln and enclosing 55 Gal oil drums to serve as retorts to produce biochar. The kiln has also been widened and we have added special collars to strengthen vulnerable areas. The retorts can be filled with off-cuts from a sawmill, garden refuse, logs or any other woody waste material. A chimney and lid creates the necessary draft to fuel the fire inside the outer ring and consume volatiles expelled from the 3 enclosed retorts.

Preparation of biochar

After browsing through many resources on techniques to prepare your biochar before mixing it with the soil we found Peter Hirst (New England Biochar) gave the best instructions: “The biochar has a micro-porous structure and it also chemically attracts organic molecules and water and tends to hold them in place. To make them available for the plants it has to be soaked or saturated with all of those elements before it goes in the ground otherwise it will be competing with the plants for the water, the microbes and the nutrients and it can actually harm the plants if it goes in raw. So we advocate mixing the biochar with soil or a good active organic compost before it goes in the soil so it soaks up its full compliment of water and nutrients and microbes so that it can make those available immediately to the plants as soon as it is added to the soil. Ultimate concentrations after some time of repeated applications of biochar will work up to about 8 to 10% biochar by weight of the soil content.” Since this system produces approximately 265 lb (120 kg) of biochar, you would eventually be able to enrich an area of approximately 250 ft2 (23 m2) or 2860 lb (1300 kg) of topsoil.

For expert hands-on advice buy The Biochar Revolution. Chapter 8 is especially relevant and gives the best advice for characterizing Biochars: attributes, indicators, and at-home tests written by Hugh McLauglin, PhD PE.

To see more benefits of biochar as a soil amendment see this post:


See this video clip of some Biochar created with the above system:



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