The invention relates to an apparatus and a method for the production of charcoal from wood chips or other particulate organic waste material. The quality of charcoal produced is suitable for use in applications such as chemical reagents, fuels, and as absorbents. The reaction vessel defines a flow path extending from the input to the vessel, through to the output from the vessel, in which the thermal decomposition of the organic material progresses as the organic material passes through the reaction vessel. The vessel includes a reaction zone for autogenous reaction of organic material in a reaction bed of the organic material, and a cooling zone having at least one inlet for supplying cooling gas into the reaction bed and an outlet to extract heated gas from the reaction bed.