Municipal solid waste combustion ash: State-of-the-knowledge

Abstract

Over the past several years there has been significant controversy concerning the proper management of the residues from combusting municipal solid waste (MSW) and their regulatory classification as hazardous or non-hazardous waste. This controversy and other factors (e.g., lack of federal guidance, heavy metal content, etc.) have resulted in inconsistent management requirements among several states and uncertainty about beneficial utilization of the residues. Heavy metal content and leaching of these metals (especially in the TCLP test) is most often cited as the reasons the material should be managed as a hazardous waste. If not managed properly, contamination of ground water by leaching of soluble salts from the ashes may also be a concern. The United States lags behind some countries in ash utilization. Although research and demonstration projects have indicated that the ashes can be beneficially utilized, less than 5% of the ashes are utilized in the United States. Other countries, including Denmark, the Netherlands, France, Germany, Switzerland, and Japan are further advanced in ash utilization and in establishment of a systematic process for evaluating and selecting disposal and utilization options. This paper discusses ash characteristics, the state of ash management in the United States, federal initiatives, results of laboratory and field characterization of leachates from the ashes, barriers to ash utilization in the United States, and international perspectives.