A briquette is a chunk of combustible material that is commonly used in igniting and maintaining a fire, either in a boiler, grill or in an open space such as a fire pit. It is commonly in the shape of a square or rectangle, but can also be found in lump form or other molded shapes. The size of the briquette is dictated by how it will be used. Larger briquettes are often used in manufacturing environment and smaller versions are mostly used in fireplaces and for outdoor food grilling purposes. The most popular briquettes are biomass and charcoal varieties.
The majority of biomass briquettes are made from sawdust or similar wood waste products. The manufacturing process generally involves compressing the sawdust and forcing it into a machine that heats it and extrudes briquettes shaped like small fireplace logs. The particles in the log are held together by a natural substance in the sawdust, so no binders are required.
Commercially produced fireplace logs favored by many homeowners are actually biomass briquettes. A similar biomass briquette is commonly used as a substitute for coal or oil to heat manufacturing plant boilers. It is often preferred over other fuel sources because its use does not release any harmful fossil fuels into the environment. Another popular reason to use biomass briquettes for boiler fuel is that they reportedly are 30% to 40% cheaper to burn than oil or coal.
Charcoal briquettes are commonly used to cook food on outdoor grills, barbecue pits and hibachis. The lump form, typically made from hardwood materials, is favored by some cooks. This preference is generally attributed to the fact that lump charcoal produces considerably less ash than charcoal briquettes.
Depending on the brand, charcoal briquettes can contain many ingredients. Besides sawdust, other wood products may be part of their composition. Starch is commonly used as a binder for charcoal briquettes. Igniting aids are frequently added to some briquettes and generally include paraffin, petroleum solvents, borax and sodium nitrate. Limestone is often added to make the ashes turn white which alerts some cooks that the fire is the correct temperature to grill food items.
A less common use for charcoal, usually in the form of large briquettes or lumps, is as a fuel for commercial road vehicles, ordinarily buses. This is a regular practice in areas where oil is in short supply or completely unavailable. Charcoal powered buses were popular in Japan immediately following World War II and are used today in parts of North Korea.