The air-borne solid particles that result from the burning of coal and other solid fuel. Using coal fly ash conserves energy by reducing the demand for typical pavement materials such as lime, cement and crushed stone, which take energy to produce. Each ton of fly ash used to replace a ton of cement, for example, saves the equivalent of nearly one barrel of imported oil. Also less greenhouse gases are produced that would otherwise contribute to global warming. Every ton of ash reused in cement products equates to nearly a ton of CO₂ savings.