Disposal Management of Preservative-Treated Wood Products

When treated wood structures reach the end of their useful lifespan they must be disposed of. Proper management of the preservative-containing wood is necessary to minimize any potential risk to human health and the environment. Treated wood products enter the waste stream in small amounts as remnants during construction activities, and at a much larger magnitude as a result of demolition. The first step in discarded treated wood management is determination of appropriate regulatory status, i.e. is should the waste be managed as a hazardous waste. Testing finds that creosote and pentachlorophenol treated wood do not typically leach preservative concentrations at sufficient quantities to be characterized as a hazardous waste in the US. Chromated copper arsenate (CCA) treated wood does often leach arsenic (As) and chromium (Cr) above hazardous waste thresholds, but in most of the US, CCA-treated wood is excluded from being defined as a hazardous waste because of a specific exemption under resource conservation and recovery act (RCRA). Other national or state specific regulations may impact disposal-end management requirements. The primary management options for discarded treated wood include landfilling, combustion and recycling. Landfilling is typically the least expensive option, but this practice is accompanied by concerns such as placement and compaction difficulties and the potential for contamination of leachate and groundwater. Recent research suggests that As leaching may pose a risk to groundwater at unlined C&D debris landfills and leachate management problems at a lined facility. Combustion is commonly practiced to recover energy from creosote and pentachlorophenol treated wood. Arsenic from CCA-treated wood may volatilizes at typical combustion temperatures so combustion facilities should be equipped with appropriate air pollution control devices. Recycling practices and extraction technologies such as bioremediation, chemical extraction, electrodialytic extraction and liquefaction have been developed, but these systems are more costly than traditional disposal options and separation of treated wood from the mixed wood stream can be challenging. As alternative treated wood products are developed and used, manufacturers should consider disposal-end management.