Municipal Solid Waste Combustion Ash: State-of-the-Knowledge

Abstract

This chapter discusses ash characteristics, the state of ash management in the US, federal initiatives, results of laboratory and field characterization of leachates from the ashes, barriers to ash utilization in the US, and international perspectives. Municipal Waste Combustion residues are generated at several points in the process of burning municipal solid waste (MSW) for energy recovery. Solids retained on furnace grates following combustion and solids passing through the grates (siftings) are generally referred to as bottom ash. The ashes from combustion of MSW are routinely classified into three categories: bottom ash, air pollution control (APC) residues, and combined (i.e., the combination of bottom ash and APC residues). The chemical characteristics of ashes and residues are the major reason for the concern regarding their classification as hazardous or non-hazardous wastes and their ultimate management requirements. Cumulative release in the field can be estimated on knowledge of the unified pH curve, availability, anticipated field pH, and the anticipated liquid-to-solid rates.