Environmental qualification of ash from wood-based recycled fuels for utilization in covers for landfills

Abstract

Combustion of recycled fuels as well as incineration of waste are excellent means to generate heat and to convert redundant objects and spent items to a form that readily lends itself to sampling and characterization, Many harmful substances may be efficiently destroyed in the process and others, such as heavy metals, may become concentrated, Consequently, it is necessary that any decision on the future fate of an ash volume be based on the content (as checked by chemical analysis) as well as on the availability (as checked by leach tests) of possibly hazardous substances, However, in the case of heavy metals in ash, an assessment based on content - and by direct application of the existing legislation - is essentially impossible to carry out in practice, The reason is that the chemical form is very complex and cannot readily be associated with the substances appearing in the data bases on hazardousness of chemical substances, Another major concern is that the assessments need be valid for very long times while the time spans available for measurements and experiments is very short in comparison, A methodology to cope with these issues has been developed and applied in a project on utilization of ash in covers, including seals, for landfills, At present, four hectares of old domestic waste have been protected at Telge Atervinning AB (Telge Recycling Plant) in a full scale test and the plans for the subsequent step include another eleven hectares, The ash originates from recycled wood based fuel (also containing paper and plastics) combusted for district heating purposes at Soderenergi AB (lgelstaverket), It was found that it is possible to identify reference substances which appear in the data bases on hazardousness and which represent the actual chemical form of the various elements in a conservative manner, In order for such an approach to be valid and robust, it was found necessary that a knowledge base on chemical composition and speciation be developed and compiled, The knowledge base is also used for predictions of the future properties and behaviour of the ash in terms of content and availability of hazardous substances as well as and permeability The Swedish legislation is the prerequisites for the work together with the National strategy of the thousand year perspective as expressed by the Swedish Environmental Protection Agency. Our legislation is based on that of the European Union and is thus very similar in a number of countries.