Secondary aluminum processing (SAP) wastes result from the smelting of primary smelting wastes and recycled aluminum products.  SAP wastes, which include ‘dross,’ ‘salt cake,’ or air pollution control filter dusts, typically contain oxidized aluminum, small particles of aluminum metal, aluminum nitrides, aluminum carbides, and metallic oxides.  In 1999, it was reported that approximately 2 billion pounds of SAP waste was landfilled in the U.S. (US DOE, 1999).

One difficulty in handling SAP waste is that metallic aluminum, when in contact with water, may cause self heating and evolution of gases such as hydrogen, ammonia, acetylene, hydrogen sulfide, and methane.  Additionally, within a landfill, the exothermic reaction may elevate temperatures to values sufficient to result in the combustion or pyrolysis of waste materials.  Several landfills in the U.S. have had significant problems attributed to SAP wastes such as subsurface heating, excessive subsidence & slope instability, engineering component failure, leachate outbreaks, gas collection & management efficiency problems, hazardous emissions, and dangerous working conditions on site for personnel.  Aside from the potential impacts on engineered systems relating to leachate collection, gas collection, and liner systems, there are potentially significant environmental and community health impacts associated with air emissions and surface water / groundwater releases.