Fly ash
Fly ash, also known as flue ash, is one of the residues generated following the combustion of coal and lignite. In the past it was released into the atmosphere through the smoke stack but pollution control requirements have put an end to that practice. It is now captured by electrostatic precipitators and stored at the point of generation, placed in landfills or recycled - where it will typically replace Portland Cement in concrete production. Typical fly ash recovery rates, for Saskatchewan lignite-fired power stations, are 31 kilograms per megawatt hour. Fly ash, depending on its use, can attract a range of prices. The best arises from concrete-quality ash which fetches $22–$49 per tonne.