It may be just a byproduct, but the state government has earned Rs 15 crore out of it. The fly ash from the thermal power plants in the state, once a major air pollutant, has now become a gold mine as construction companies and cement manufacturers compete to take a major chunk of the byproduct. The AP Power Generation Corporation (Genco) has earned Rs 15 crore by selling this fly ash. This is usually used to make bricks or add as a mixture to cement, used for construction or laying roads. More than nine million tonnes of ash was sold this year by Genco.