- (Disambiguation: In Dwarf Fortress, bituminous coal is not the same as "coal" - see that article if desired.)
Fuel, refined coal, and just coal are three in-game terms that refer the same thing, any unit of charcoal or coke, the two fuels used to power high-temperature industries, namely metalworking, glassworking, and pottery. One unit of either of these fuels is required for every task at a conventional (non-magma) smelter, forge, kiln, or glass furnace. Magma versions of these facilities do not need fuel, and in fact cannot use conventional fuel to power them if their magma sources fail. Refined coal is also needed as part of the pig iron and steel creation process (see below).
Although both "charcoal" and "coke" are simply listed as such when viewed in the game with the z-stocks menu, and can be used to build vertical bars, and so a unit of fuel is usually considered "a bar". To place bars of fuel in a stockpile, create a Bars/Blocks stockpile, or a custom stockpile with "coal" (found in the "Bars" sub-category) nabled and ermitted., they are found under the "bars" section of the
 Fuel: charcoal and coke
The two sub-types of fuel are charcoal and coke, and they are effectively identical for in-game purposes, even if they come from different sources and have different in-game names. Whenever you see "fuel", "refined coal" or "coal" in-game, those refer to either charcoal or coke - they are interchangeable, and either one will serve the same purpose, as fuel for the desired activity. (Bituminous coal is not the same as "coal", and does not refer to fuel, but can be converted into coke at a Smelter.)
Both charcoal and coke come in bars, and are stockpiled in Bars/Block stockpiles if the "coal" entry is selected within the "Bars" section. There is currently no way (or need) to distinguish between the two when designating stockpiles.
At the risk of repetition, but to be perfectly clear - despite the different names, there is no distinction between charcoal and coke for any workshop-related activities. Both are "refined coal" or "coal", or just "fuel". The only actual difference between charcoal and coke has to do with Elven traders - selling them charcoal will offend them, but coke will not.
Charcoal and coke are, of course, not fire-safe building materials.
 In-game usage
The different terms are found in different places in the game, but all refer to the same thing, bars of either coke or charcoal.
"Fuel" is sometimes used informally in the forums and in various wiki articles. Since some understandable confusion can arise over the usage of the various terms "refined coal", "coal fuel", "coal", "charcoal" and "coke" (and also "bituminous coal", which is not a fuel), the simple umbrella term "fuel" will be used in the explanations in this article.
At a conventional (non-magma) smelter, if you try to add a smelting task and have no fuel, you will see the message:
- No tasks available
Check for raw material access
and fuel if necessary
- (Note that this message will also be seen if there is no path to your workshop or needed materials, including fuel.)
You will not be allowed to add any tasks to any conventional smelter until that workshop has access to at least one unit of either charcoal or coke. (However, if you have just one bar of un-used fuel, you can queue up as many jobs as you want - see next...)
If you have queued up multiple tasks and then run out of fuel, you will get an announcement similar to:
"Urist McFuelUser cancels job: needs refined coal."
Note that a forge or glass furnace will let you add tasks if you have no fuel, and only once a dwarf arrives and finds they cannot complete that task will you get the announcement to that effect. You will get one announcement for each un-fueled task that is unable to be completed. Jobs are canceled when there is no fuel.
When you get either of these messages, you need more fuel - either charcoal or coke will serve equally well.
 The two sub-types of fuel
There are 2 sub-types of conventional fuel - charcoal and coke. Charcoal and coke are identical in use - a single unit of either one powers one activity at a conventional smelter, forge, kiln or glass furnace, or can serve as the ingredient to make pig iron or steel. They are completely interchangeable, the only difference is their source.
 Charcoal, from wood
Charcoal is created at a wood furnace using one wood log by a dwarf with the Wood burning labor enabled. Skill levels in the Wood burner skill are not required but reduce the time required for this activity.
 Coke, from bituminous coal or lignite
Coke is a type of refined coal, and is identical to charcoal for all game purposes. It is created at a smelter using one unit of fuel by a dwarf with the Furnace Operating labor enabled. Skill levels in the Furnace operator skill are not required but reduce the time required for this activity.
Coke can be created from bituminous coal, producing 3 coke (net gain of 2 fuel), or lignite, producing 2 coke (net gain of 1 fuel). Magma smelters do not require conventional fuel for this process, and so the net yield for each is effectively +1 greater.
- Required Building - Smelter or Magma smelter
- Required Labor enabled - Furnace operating
- Required Material - Bituminous coal or lignite
- - plus one unit of fuel per unit smelted, if at a conventional smelter
Bituminous coal blocks and lignite blocks (sometimes offered by traders) can neither be used as fuel nor converted into fuel or back into stones in any way. They can only be used for standard block purposes -- though they are of course not fire-safe!
Because you need fuel in order to refine fuel, you will probably need to create at least one unit of charcoal at a Wood Burner first.
 Magma facilities
Magma replaces conventional fuel for magma smelters, magma forges, magma kilns and magma glass furnaces. No fuel is needed, nor can it be used, for activities at these facilities. Note that you will still need charcoal or coke for smelting bars of pig iron and steel. (And see next section.)
 Pig iron and steel production
Note that when smelting pig iron or steel at any location, one unit of either charcoal or coke is required in the reaction (presumably as carbon). Again, there is no distinction - both charcoal and coke serve equally well in the production of bars of either. An additional unit of fuel is needed to power the furnace at conventional (non-magma) smelters.
[MATERIAL:COAL] - reconstructed from data extracted from memory [STATE_COLOR:ALL:BLACK] [STATE_NAME_ADJ:SOLID:coal] [STATE_NAME_ADJ:SOLID_POWDER:coal powder] [STATE_NAME_ADJ:SOLID_PASTE:coal slush] [STATE_NAME_ADJ:SOLID_PRESSED:pressed coal] [BASIC_COLOR:0:1] [BUILD_COLOR:0:0:1] [TILE_COLOR:7:7:1] [MATERIAL_VALUE:2] [SPEC_HEAT:409] [IGNITE_POINT:11440] [SOLID_DENSITY:1346]