Biochar “kiln” made from an old 4’x12’x 3/16″ thick scrap steel tank, trailer axles, a few trunk jacks from the auto wreckers, and a new 2″ ball hitch receiver. Great for small-medium size production, just wheel the wagon up to your feedstock pile , fill it up, start it at the top and keep on adding til the pile is gone. There are many better and more elegant options for making biochar, but at this scale, its operation is relatively time efficient, though the material production and carbon sequestration efficiencies are not the best. But it only cost a whopping $100 in materials to make!