I see this stuff everyday, I work at a coal fired power plant. They don't rail it in here, they have their own mines and dig Lignite, a young coal.
Our other plant rails in a 100 car train every two days or so, they get whats called Western Coal, they burn a mix of lignite and western. The western burns cleaner and at a higher BTU, we sell one of the by products called Fly Ash, amazing stuff, main use is in concrete. My locations main customer is a roofing plant, they use the ash in the process of making shingles.
Ever get some time and want to educate yourself, google fly ash, its wild stuff, specially the class c, we are class f here.
The class c you can put in a cup, add water and it will be rock hard in under 10 minutes.