Multi-elemental analysis of wood waste using energy dispersive X-ray fluorescence (ED-XRF) analyzer

The performance of solid wood and wood-based materials is generally increased by applying chemical and physical treatments; however they may compromise the recyclability of the products reaching their end life. Among the wide range of chemicals applicable to wood-based materials some are source of concern and a few (e.g. Chromate Copper Arsenate) are considered to be dangerous waste. This work focuses on the elemental analysis of wood residues developing a survey on contamination levels of wooden materials, intended either for quantifying wood not polluted that may be re-used as “virgin” raw material, or as a preliminary step of an automated sorting method using Energy Dispersive X-ray Fluorescence (ED-XRF). The analyses are referred to elemental concentration reported for natural solid wood and to those thresholds set by law. In a sampling carried out mainly in north Italy, 336 wood waste specimens were collected, classified using descriptor fields and analyzed with ED-XRF technique, implementing a validation method for short scan time. Roughly 84 % of the specimens comply with the EU decision (Ecolabel) on heavy metals, ranging from 94 to 63 % (fibreboard, hardwood, softwood, plywood, particleboard recycled and particleboard). Most detected heavy metals originate from furniture and building materials, whereas packaging and specimens of unknown origin presented no major concern. Very high concentrations of Cl, Pb and Cr were found. The technique has been proved to be effective with certain limitations. Great attention should be taken to manage wood waste critically polluted in some cases and possible source of clean raw material in others.