Coal with a good blower is hotter than propane. It will get the surface of iron up to white hot for forge welding. When the old time blacksmiths couldn't get coal or good charcoal, some of them used green chestnut.
Good forge coal has to be low in sulpher and not produce a lot of clinkers. Impurities like that will prevent a good forge weld. If you're not doing forge welds, your choices in coal more plentiful.
BTW, a forge weld is done by hammering the two pieces to be joined to a scarf joint, then heating them to white heat, with some kind of flux to keep the air away. Borax works well, but some smiths used clean sand. It would melt down to a glass coating across the surface of the metal. When both pieces were ready, they were lined up and struck together with a heavy hammer. The classic shot of sparks flying off the anvil only happens at white heat. Typically a forge weld, unless the smith is playing to the camera.
Incidentally, I did my first lost-foam casting this morning. It's getting late, so I'll post it in a new thread tomorrow.