Charcoal Grill

Step 1: Fuel Source
Coal is formed by natural earth processes just like petroleum and natural gas. As plants and animals die, their organic matter builds up and is covered with layers of sediment. Over time, the temperature and pressures the organic matter is exposed to will transform it into coal.

The composition of the organic matter determines whether it will form coal, petroleum or natural gas. Wood tends to form coal based on its high levels of carbon and relatively low levels of oxygen that get trapped underground with the wood. However, any organic matter can form any hydrocarbon based on a myriad of factors, including the environment and surrounding material. Coal formed underground varies in its quality, which is based on the carbon content. The higher the carbon content, the more valuable the coal.


In our grill we will not be using natural coal, as it is better suited to industrial purposes. Charcoal used for grills is a specific type of man-made coal that is produce by heating wood in a low oxygen environment. The result is charred wood, which is what we call charcoal. This combustion reaction for wood is shown below.
 6 C10 H15 O7 (s) + heat → C50 H10 O (s) +10 C H2 O

Notice the difference in the chemical formula between the wood we are heating and the char we are producing. The char is almost completely made up of carbon. When the reaction is done, you have a mainly-carbon rock and are ready to get the grill going! The two most popular forms of charcoal are charcoal briquettes and hardwood lump.

Charcoal briquettes are the most popular and widely used form of coal. Charcoal briquettes have a high degree of symmetry which leads to a nice even burn. However, they also use fillers and binders to achieve their uniform shape and maintain their burn. They don't have a distinct flavor of their own, but will generally lead to a better flavor than using a gas grill. Whereas propane burns as a flavorless gas, charcoal smoke has a distinct smell which imparts flavor on the meat.
Hardwood lump charcoal is made using the same process as briquettes, however it uses chunks of wood that do not have a uniform shape. It is also not as dense as briquette. Both of these differences are due to the lack of fillers in hardwood lump. While this type of charcoal doesn't burn as long or evenly as briquettes, these are small factors compared to the amazing flavor one can achieve using different types of hardwood lump.

Step 2: Converting Charcoal to Heat
Charcoal grills are more simple to use as their are no gas lines or tanks involved, and we need only to ignite our coal. Once our coal is lit it will continue to burn. However, many things burn when we light them so what is it about coal that makes it so special and valuable as a heat producing source?

Coal is made up of carbon and hydrocarbons, which produce relatively large amounts of heat when they undergo combustion. Since we know the molecular formula for char, we know that it is mostly carbon. The combustion reaction of carbon is exothermic, which means it releases energy. In our case, this energy is released in the form of heat. The combustion reaction of carbon is shown below.

C + O2 → CO2 + heat

The coals maintain their burn for two reasons. First of all, they are a dense source of carbon fuel.  Secondly, the combustion reaction of char is relatively slow due to the large amount of carbon in one molecule. The result is a steady, long-lasting supply of heat for a  seemingly small amount of fuel. 

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