The auto-thermal process as the most realistic option has been proposed for the participation
of local communities in using biochar to build soil fertility, especially in developing countries.
It is lower cost, and easier and simpler than pyrolysis systems where ratios of solid, liquid
and syngas products have to be optimised. A comparison of three alternative options has
recently been investigated for the carbonisation of biomass wastes from tree plantations: a
drum kiln, a Hume pipe kiln, and a brick kiln (Okimori et al., 2003; Ogawa et al., 2006). For
wood, 24% of wood mass was converted to biochar of 76% carbon content at 400 to 500°C,
but carbonisation at 600°C gave 28% biochar with a higher carbon content of 89%. The 50%
of feedstock carbon stabilised in each case was similar to the maximum yield obtained in
slow pyrolysis.
Brazil has the largest concentration of industrial charcoal manufacture. This is associated
with the pig-iron (smelting) industry, where substitution of charcoal for fossil-derived coke has
been achieved in a number of very large projects under the Clean Development Mechanism,
and associated with large-scale plantations of eucalypt.