Anybody who’s grilled with charcoal knows what it’s like — black, hard, long-burning, and relatively smokeless. It gets those characteristics from the way it’s made, a centuries-old process that essentially involves heating carbon-based substances, like wood or bone, in an environment with little or no oxygen. This process removes water and gases that were in the original material, creating “char.” The char is then mixed with other substances, including binding materials such as corn, and shaped — often into briquettes or other shapes.
Charcoal literally goes through a trial-by-fire process, which makes it, in turn, a substance that can be burned to deliver steady, reliable, and long-lasting heat. There are three basic stages to the production process: charring, shaping, and bagging.
In the first stage, wood, bones, or other carbon-rich materials are dried and then subjected to extreme heat of around 840° to 950°F (450° to 510°C). This is accomplished by placing the materials either in a kiln or a continuously-fed furnace called a “retort.”
In the kiln or batch method, there is a cooling period, in which the air and exhaust vents are closed off and the material is left in an oxygen-free environment. During this cooling off time, the materials becomes char.
In the retort or continuous method, the materials are fed through a furnace with multiple hearths, and mechanical arms stir them to make sure they burn evenly. At the end, the char is sprayed with cold water. Coal can also be charred by crushing carbon-rich materials, then drying and heating them to about 1100°F (590°C), and then cooling them by air.
The second step in making charcoal is shaping it, typically into some form of briquette. To make these, the char is mixed with other ingredients, such as a starch binder like wheat. The mixture is then dropped into a press that cuts it into standard briquette shapes. These briquettes then go through a dryer. Charcoal is sometimes also extruded into larger, log-like shapes.
After the material is shaped and cooled, the briquettes are bagged and sent off to store shelves, industrial plants, and other destinations.