Hyperspectral imaging based procedures applied to bottom ash characterization

Bottom ash from Municipal Solid Waste Incinerators (MSWIs) is mainly land filled or used as material for the foundation of road in European countries. Bottom ash is usually first crushed to below 40 mm and separated magnetically to recover the steel scrap. The remaining material contains predominantly sand, sinters and pieces of stone, glass and ceramics, which could be used as building material if strict technical and environmental requirements are respected. The main problem is the presence of residual organic matter in the ash and the large surface area presented by the fine fraction that creates leaching values, for elements such as copper, that are above the accepted levels for standard building materials. Main aim of the study was to evaluate the possibility offered by hyperspectral imaging to identify organic matter inside the residues in order to develop control/selection strategies to be implemented inside the bottom ash recycling plant. Reflectance spectra of selected bottom ash samples have been acquired in the VIS-NIR field (400-1000 nm). Results showed as the organic content of the different samples influences the spectral signatures, in particular an inverse correlation between reflectance level and organic matter content was found.