Charcoal

Charcoal is a type of fuel. it is produced in the Charcoal burner by burning wood in the absence of oxygen, driving off all impurities and leaving mostly pure carbon. It is a type of Resource.

Wood or Charcoal
Charcoal has a net fuel efficiency that is three times higher than regular wood, and is generally considered the better choice.
 * First level charcoal clamps converts wood into charcoal at a 4:3 ratio.
 * First level foundry uses 4 times more wood than charcoal in its production.
 * The efficiency of charcoal divided by the wood to charcoal ration gives us (4/(4/3)) = 3.
 * This gives us an overall efficiency that is 3 times that of wood.

Peat
Charcoal can also be made by the Soil miner.

the Soil miner is able to gather Peat a resource sometimes present in Nordic swamps.

The technolegy Soil collectors usualy comes in before Charcoal (Knowledge),

The tech for Charcoal is not nessasary for the Soil miner to collect peat and make it into charcoal.