We burned coal for heat on the coldest of nights when we lived off grid on a ranch in the mountains of colorado. We only used it if we absolutely had to as its super stinky, dirty and gross. We would get maybe two or three big chunks a year that weighed maybe 1-2 lbs. You can go up into the mountains and see the huge mountains of coal from the mines that have shut down. There are also rows of of coke ovens in monument canyon (used in the 19th century to turn coal into smelting iron)