system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can charcoal burn when it's made from from burnt wood?

Shouldn't all the innate energy already have been used up during the initial combustion leaving you with material equivalent in flammability to ash.
gpt
Charcoal isn't burned wood. It is produced by heating the wood in an oxygen free environment, which prevents it from burning. The heat causes liquids and gases to be expelled from the wood, leaving a solid residue that is made up mostly of carbon, which is more combustible than plain wood.