Classification of ash as hazardous or non-hazardous waste

Combustion and incineration are utilized extensively in Sweden for the generation of heat and electricity. Substantial volumes of ash with varying chemical composition are also generated in the process. Classification of such ash as hazardous or non-hazardous under the European union legislation is, in principle, a “mission impossible” since the chemical forms of the inorganic components are very complex. Consequently, a method has been identifiedaccording to which reference substances are selected such that they represent the hazards of the actual forms of those trace elements that might influence health and the environment. The reference substances have been selected such that the hazard is not underestimated, that the result becomes reasonable realistic and that the evaluation is feasible to carry out. There areindications, especially with regard to ecotoxicity, that the method is overly cautious, and a potential is identified for combining testing with information from Authority data bases. It is explained and exemplified that ash may be very susceptible to ageing, and that this in many cases, and for most of the elements of interest, may improve the properties considerably. This not only influences the status of an ash with regard to the acceptance criteria for landfilling, butalso influences the classification. Leach properties are important when the degree of solid solution is to be assessed. Elements with similar properties, especially regarding their ionic radii, tend to exchange for each other even in solids. The effect is strongest for those elements that are the lowest abundance. Solid solution effects may lead to that trace elements become as inaccessible as the major elements in a certain crystalline phase. Iron(hydr)oxides and other ironrich phases frequently act as sinks for chromium, nickel and zinc, and in many cases this implies that most of these elements may not contribute to a classification as hazardous. The method has been applied to around 30 facilities with typically several ashes at each facility. It is concluded that this approach has lead to that many ashes have been classified in a cautious bur also reasonably realistic manner which at the same time has been practical.Godkänd; 2014; 20150523 (rolsjo