carbonisation

Carbonisation, or carbonization, is the process of converting an organic material into a carbon-rich solid by heating it in a limited or zero-oxygen environment. It is a form of pyrolysis in which volatile compounds are driven off and the remaining material becomes char with a high proportion of carbon and an increasingly aromatic structure.

Temperatures typically range from about 400 to 1000 °C, depending on feedstock and desired product. At lower temperatures, more volatile matter remains, while higher temperatures promote greater carbonisation and, in some cases, graphitic ordering. The solid residue is commonly called char, charcoal, or coke, while gases and liquids are collectively called pyrolysis products.

Feedstocks include wood and other biomass, coal, and certain plastics or polymers used in high-temperature processing. In biomass processing, slow pyrolysis favors char production (biochar) for soil amendment and carbon sequestration, whereas fast pyrolysis produces liquids and bio-oil with a smaller char yield. In industry, coal is carbonised to produce metallurgical coke used in metal smelting.

In materials science, carbonisation also refers to heat treatment of carbon-rich precursors—such as polyacrylonitrile fibers—under inert conditions to form carbon fibers with high strength and stiffness. The resulting carbon materials find use in filtration, adsorption, energy storage, and structural composites.

Environmental and practical considerations include control of emissions, energy input, and the potential for carbon sequestration via stable char in soils. Historically, char making and coke ovens played key roles in metalworking and fuel supply before modern gas and oil technologies.