The System
Commercial production of biochar is possible here. But these family farms are all less than an acre. My goal was to design a biochar system to match the existing scale of operations and power sources (solar and human power).
The system I designed has four parts:
trail building, to access steep terrain
a portable kiln, to make biochar where the brush is
a hand-powered charcoal grinder
a powered wheelbarrow, to neutralize the terrain
This system was designed to be affordable and accessible. It can be adapted for other conditions, in whole or in part.
Trails
To approach the problem at this scale, the first step was to build trails, paying careful attention to grade for wheelbarrow access. This was begun in year one (2010). Finished trails are surfaced with wood chips.
Kiln
The kiln design is licensed by Vuthisa in South Africa. It is a flame cap type, consisting of a steel cylinder in three flanged sections joined by bolts, plus a lid. Snuffing the fire with the lid and sealing air leaks with mud makes water unnecessary for extinguishing the fire. Most of the forest is too far from water sources. (Inaugurated in 2015)
Grinder
The grinder is my own design, based on an obsolete compost grinder (Rotocrop). It makes very little dust and converts all the char to a suitable size for biochar using the least work. The hopper holds a wooden cylinder with a 1/4" gap on either side, studded with decking screws and turned by hand. It fits on the lid of an ordinary 5-gallon bucket. An Autodesk version of the fully assembled model is available here. This work is licensed under a Creative Commons Attribution 4.0 International License. (Built in 2018) There is now a fruit grinder made by EJWOX that appears to be capable of the same thing.
Char is made during the winter rainy season and left outdoors. By the spring, it has an ideal moisture content for grinding with minimal dust.
Powered Wheelbarrow
To move the kiln, char, and other materials in the steep terrain, I retrofitted a wheelbarrow with a powered hub from China and a 24V battery that recharges from the house solar system. (Completed in 2019)
The wheelbarrow facilitates transport of various loads. Char is moved to a central location for grinding and inoculation. Trails are surfaced with chips from occasional chipping operations along the access roads. Firewood is brought to the cabin. The three sections of the kiln itself can be strapped on and carried, not to mention tools, soil, and anything else that fits in the bin.
This is the Wellmade HD6 brand of wheelbarrow, which is widely available. Modification included cutting slots in the dropouts for the chamfered spindle so that the hub can turn against them, plus turning handle extensions on a lathe for the controls, which are designed to fit scooter handlebars. The battery and controller are strapped on with a tie-down. The electrical parts are not weatherproof, but the modifications can be reversed in about five minutes.