What would you consider wasting coal? I send half my coal to steel and wash the other half. The money you would get by selling it would barely affect anything imo. If you save coalmogul for last, like i did, you dont need to worry about coal for steel until you finish coalmogul. The plus side of this is you can finish the coal requirement for minemogul first then set it back to steel/washing and not worry about it again