Metals content of recycled construction and demolition wood before and after implementation of best management practices.

A limitation to recycling wood from construction and demolition (C&D) waste is contamination of metals from the inadvertent inclusion of preservative treated wood, in particular wood treated with chromated copper arsenate (CCA) and newer copper-based formulations. To minimize contamination many regions have developed best management practices (BMPs) for separating treated from untreated wood. The objective of this study was to evaluate the fraction of preservative treated wood in recycled C&D wood after the implementation of BMPs, using Florida as a case study. Methods involved collecting recycled C&D wood samples from throughout the state, measuring metals concentrations (As, Cu, and Cr) in the samples to compute the fraction of recycled wood treated with waterborne wood preservatives, and comparing measurements with those taken prior to the formalization of BMPs. Metals concentrations were measured using two methods, one based on traditional laboratory digestion methods and another using a more rapid hand-held X-ray Fluorescence (XRF) device in the field. The proportion of waterborne preservative-treated wood in recycled wood products has reduced significantly in the intervening 20 years (from 6% to 2.9%), and the fraction of CCA-treated wood has been reduced even further, to 1.4%. The remaining fraction of waterborne preservative-treated wood is comprised of new formulations of copper-based preservatives. This suggests that restrictions from the wood preservation industry and best management practices implemented at recycling facilities have been effective in reducing heavy metal contamination from pressure treated lumber in recycled wood products.