Utilization and Disposal of Fly Ash and Other Coal Residues in Terrestrial Ecosystems: A Review

Abstract A major shift to coal as an energy source adjunct with more stringent air quality standards will result in the increasing production of vast quantities of the already difficult‐to‐dispose coal residues in the United States. Since coal residues contain potentially hazardous substances, improper handling and disposal could cause undesirable environmental effects. This report intends to summarize impacts of land‐oriented utilization and disposal of various coal combustion residues. The physical and chemical properties of coal ashes are dependent on the coal's geological origin, combustion conditions, efficiency of particulate removal, and degree of weathering before final disposal. Coal residues, applied on cropland, are not practical sources of essential plant nutrients N, P, and K; however, they can effectively serve as a supplementary supply of Ca, S, B, Mo, and Se to soils. Fly ash could also be an effective amendment in neutralizing soil acidity. Many of the observed chemical and biological effects of fly ash applications to soils resulted from the increased activities of Ca 2+ and OH − ions. Most unweathered fly ashes, especially those coming from the subbituminous and lignite coals of the western U.S., are high in these constituents and usually will cause high soil salinity. The accumulation of B, Mo, Se, and soluble salts in fly ash‐amended soils appear to be the most serious constraints associated with land application of fly ash to soil.