Clod or “natural” charcoal is produced by partially burning wood or by heating wood without oxygen. Unlike charcoal briquettes, clod charcoal contains no additives and is not compressed or molded; instead, it retains the shape of the wood from which it was produced. Clod charcoal is made from either natural wood (from trees or saw mills), or from processed wood (from building material scraps, furniture remnants, pallets, flooring scraps, etc.).
If unlimited oxygen is available, clod charcoal will burn hot and fast. Therefore, clod charcoal is best suited for grills that allow the user to control the airflow, thus regulating the temperature and speed at which the coals burn.
Charcoal briquettes consist of crushed charcoal mixed with various additives that improve combustibility and bind the charcoal together. The mixture is compressed into uniform, pillow-shaped chunks, which generally burn slowly at a consistent temperature, regardless of airflow. Therefore, briquettes are useful when cooking on an open grill or whenever airflow can’t be controlled.
Manufacturers now offer a variety of charcoal briquettes, including briquettes infused with wood flavors and instant-light briquettes which can be ignited without lighter fluid. Charcoal briquettes are readily available in supermarkets, and are usually cheaper than clod charcoal.
Some experts advise against using instant-light charcoal since the additives in these briquettes can leave a bad taste in your food and can be harmful if not fully burned off. If you do use instant-light charcoal, be sure to let the charcoal burn until all the accelerants are eliminated.
Other grillers avoid charcoal briquettes altogether, asserting that the additives in briquettes give foods a bad flavor and are harmful when released into the air.