Handling of impregnated waste wood and characterization of ash residues after combustion of the wood

In the next ten years the amounts of waste wood impregnated with Cu, Cr and As (CCA) is expected to increase dramatically world wide. CCA has been widely used for wood preservation since the early 1950s and because the fixation of CCA in the wood is good, the concentration of CCA is still high, when the wood is at the end of service. In some countries e.g. Denmark and Norway, the use of As for wood preservation has recently been forbidden and both in EU and USA restriction on the use of CCA has been given. However, there will still be a lot of older CCA impregnated wood in the waste in many years to come. Development of safe methods for handling of the CCA impregnated waste wood is necessary mainly due to the content of As. The present paper outlines some treatment methods for the waste wood and problems of handling impregnated waste wood as e.g. sorting impregnated wood from not-impregnated wood Combustion of CCA treated wood together with municipal solid waste is problematic. To avoid emission of As it is necessary to install special flue gas cleaning systems at the plants. Furthermore the result will be a very large amount of ash residues enriched with Cu, Cr and As compared to the ash composition of today. Thus it is beneficial or even necessary to sort the impregnated wood from other waste, which is already done in e.g. Denmark and Finland, and treat the impregnated wood separately. Thermal treatment of the wood in plants equipped with special flue gas purification systems is one treatment method and residues from such processes (combustion and pyrolysis) are characterized and extraction experiments are performed. Knowledge of the characteristics of such toxic residues is of crucial importance in order to ensure safe handling.