Fly Ash Discussion, page-12

another variable, related to flyash supply and may be trivial at this stage, is competition for use, as more uses are being found to it in addition to its pozzolanic properties in the construction industry

fun fact of the day from the the American Coal Ash Association - almost half of the concrete pruduced in the USA is made from flyash

source https://www.acaa-usa.org/About-Coal-Ash/A-Sustainable-Future

another thought and also trivial in a situation of abundance is a reduced supply in the setting of a prolonged low natural gas price, which may make the economics of electricity generation from gas better than coal for some plants