An example managed biochar kiln includes drum walls, a drum floor, and a lid formed to be fitted to a top edge of the drum walls to close a top end of the drum walls and form a combustion chamber between the lid, the drum walls, and the drum floor. The example managed biochar kiln also includes a chimney stack attachable to the lid. The example managed biochar kiln also includes a valve on the lid operable by an electronic controller to vary airflow through the chimney and out of the lid.