Chromated copper arsenate timber: A review of products, leachate studies and recycling

Large volumes of chromated copper arsenate (CCA)-treated wood are disposed of in lined and un-lined landfills across the world. Studies regarding the disposal and reuse of CCA-treated timber date back to the 1980s. This paper provides a comprehensive overview of the research undertaken regarding reconstituted chromated copper arsenate-treated timber products, and considers the relevant health issues and disposal techniques, such as incineration and thermochemical conversion, as well as long-term solutions for the managing of chromated copper arsenate-treated-waste wood. The results from reviewing the literature regarding reconstituted timber products consisting of CC-treated timber such as particle board, cement-bonded particle board, flake board, remediated wood composites, wood-plastic composites, and wood-cement composites revealed that products such as particle board, wood-plastic composites and flake board composed of CCA-treated timber show considerable promise. Further research is required to determine the optimum percentage of CCA-treated timber in wood-plastic composites to minimize leaching while attaining suitable physical and mechanical performance, and to evaluate the durability of reconstituted chromated copper arsenate timber products via severe accelerated aging tests. Several CCA-waste wood disposal methods were investigated in the form of extraction and destruction techniques including thermochemical conversion (pyrolysis, gasification), incineration, co-incineration and combustion. Such management techniques demonstrate promising, feasible, future solutions providing the ability to trap arsenic gas, recover metals, and create secondary energy forms. However, more research is required, especially regarding resultant arsenic compounds and their volatile behaviours. Industries that create and sell chromated copper arsenate-treated wood products are encouraged to follow the United States Environmental Protection Agency leachate testing procedures (Methods 1314 and 1315, published in 2013), since these methods are more accurate at evaluating the leaching behaviour during their lifetime, and various disposal scenarios that reflect differing pH values and liquid to solid ratios.