Depends on your definition of "radioactive waste". From the figures I've seen, coal fly ash is pretty similar to say granite in terms of overall activity and is

Depends on your definition of "radioactive waste". From the figures I've seen, coal fly ash is pretty similar to say granite in terms of overall activity and isotopic composition. It doesn't seem to enhance the concentration to the same worrying levels that say rare earth mining does, probably because the radioisotopes and all the other unwanted non-carbon trash is heavily diluted by all the carbon.