The charcoal kiln produces coal, not charcoal, well, it’s not very detailed. When there are many coal resources on your map, charcoal kilns are not worth building. Charcoal kiln consumes firewood to produce coal, but coal can’t replace firewood for heating. I think charcoal is more efficient than firewood in heating.
it can make charcoal kiln useful, Charcoal can also be used in smeltery, but the effect is not as good as coal. Here are my suggestions.
Distinguish between charcoal and coal
Charcoal kilns can be used to produce charcoal with higher heating efficiency than firewood.
3.Charcoal is inferior to coal in smelting.
（My English level is poor, because my mother tongue is not English. Please understand.）
I think this limitation is due to the usage in recipes to make advanced products like ingots, weapons, cobbles, and so on. But indeed you can also add recipes to make them using charcoal too.
Anyway the most important thing is that if they implement this difference, they have to give the possibility to prevent citizens to use charcoal for heating, leaving it for other usages. This was amongst the most critical issues in Banished, for example, when you run suddenly out of tools because citizens compete with fundries for the coal usage, making things frustrating.
But I think if a player encounters a map without coal, it is highly probable that the player will change to a new map. So when the charcoal kiln can come in handy, it should be when the players on the map use up the coal resources in the late stage. This is my personal idea.
I have a map with 1 charcoal mine unfortunately. I ALWAYS need firewood. I built this building and its the only building I have toggled off because I just can’t spare the wood. It seems 90% of the building want to take my wood lol. I agree on making it a separate resource.
