The amount of heat released during combustion is measured in units of energy per unit of the substance.
Measured in approximate Calorific value the answer to this question is charcoal.
FUEL = kJ/g
Dry Wood = 19
Coal (mineral of fossilized carbon) = 28-33
Coke (made from coal is smokeless) = 28-30
Charcoal (made from wood) = 29-30
Fuel Oil = 42-44
Kerosene = 46
So apart from the fact that Charcoal burns hotter than burning wood it is also a better fuel to use in the BBQ because it is mostly smokeless and a lot cleaner than burning wood.
Do note that it is a common misconception that all wood based charcoal burns with the same heat intensity and duration. Yes there are many different types of fuel clasified under the general heading of charcoal, but they have different characteristics.
Differences in Charcoal
Lump Charcoal is basically natural material looking like branch or root material. Can be brittle and irregular in shape and different hardwoods provide variations in heat and longevity as a fuel source.
Pillow shaped briquettes is compressed and binded (usually with starch) together. Some may contain brown mineral coal, borax, sodium nitrate, limestone or other additives.
Compressed logs, sticks or briquettes are made by extruding sawdust (usually wood but can also be other like coconut shell) under pressure without binders or additives. The sawdust can be either raw or carbonized prior to being compressed.
Japanese Charoal is charred wood which has gone through a process of rapid tempurature rise followed by rapid cooling leaving a smooth hard surface. This type is considered high grade charcoal and yields long burn times. There are 3 types - White charcoal (Binchotan), Black charcoal and Ogatan (made from sawdust).
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