Kolning

Kolning is the process of producing charcoal by carbonizing wood or other biomass in a limited-oxygen environment. The term is Swedish in origin and is commonly translated as charcoal production. In a typical kolning operation, logs or billets are stacked in a kiln, pit, or mound, and air supply is restricted to prevent full combustion while heat drives off volatile substances.

During heating, water, tar, and other volatile compounds are released as gases and vapors, some of which are burned within the kiln to help sustain the temperature. When most volatiles have been driven off and the remaining material has cooled, the product is charcoal: a carbon-rich, porous, solid fuel with a high energy content.

Historically, kolning was essential for metal production, since charcoal served as the primary reducing agent in iron and steelmaking before coke became widespread. Kolning was practiced in many regions with specialized kiln designs and required careful control of heat and airflow.

In modern industry, large-scale kolning has largely been replaced by coke-based processes and other fuels. Small traditional kilns and demonstrations survive in some areas, and charcoal produced by kolning continues to be used for cooking, artistry, filtration, and soil amendment in the form of biochar or activated carbon. Environmental concerns include deforestation and smoke emissions, prompting regulation and the adoption of more efficient, lower-emission methods.