LAUSR

The amount of biomass-derived ashes is expected to rise in the EU due to targets to increase the use of renewable energy resources. To promote the reuse of biomass ashes, a regional case study of natural ageing of approximately 1 year was carried out on two landfill fly ash materials originating from wood and wood/peat. The results showed that leaching behaviour differed considerably between the fly ashes. Natural ageing had beneficial effects on the leaching properties of wood fly ash. The leached concentrations of sulphate, chloride, Cr and Mo decreased significantly in this residue. In peat and wood-derived fly ash, natural ageing decreased the leaching of Cr, but had no significant effect on the leaching of Mo and chloride. It was also notable that the leaching of sulphate increased in wood/peat fly ash by more than 130%, exceeding the upper limit value given in national legislation for a paved structure. To comply with the limit values of national legislation concerning the recovery of waste in earth construction, natural ageing alone was not shown to be a sufficient method to reduce the leaching of harmful elements in biomass-derived fly ashes and, thus, further treatments are required.