Ash

The non-combustible residue of a combusted substance composed primarily of alkali and metal oxides.

Residue remaining after ignition of a sample determined by a definite prescribed procedure. (Source: Domalski, E.S.; Milne T.A., ed. Thermodynamic Data for Biomass Materials and Waste Components. The ASME Research Committee on Industrial and Municipal Wastes, New York: The American Society of Mechanical Engineers, 1987)

The mineral content of a product remaining after complete combustion.