The most widely used wood preservative since the early 1970's has been chromated copper arsenate (CCA), resulting in nearly 80% of all treated wood products in North America being treated with CCA. However, by late 2003 CCA-treated wood was restricted to industrial applications, leading to a considerable increase in the volume of CCA-treated wood slated for disposal. Landfilling was an acceptable means of discarding CCA-treated wood products until recently, which has lead to approximately 24 million tons of CCA waste. Problems associated with soil and groundwater contamination, caused by CCA-metals leaching from landfills, have generated the need for an effective and efficient disposal method for CCA-treated wood.

In this research, fast pyrolysis is evaluated as a means of recycling CCA-impregnated wood waste. A primary goal is to concentrate the CCA components in the bio-oil, for possible re-use in wood preservatives, while recovering the energy value of the wood. An easily modified lab-scale pyrolysis system, capable of operating in the desired temperature range under atmospheric and vacuum conditions, was designed. The system allows for the collection of each pyrolysis product so that complete mass balances on the metals can be performed, tracking the fate of the CCA metals. Initial testing was completed with the system in a batch reactor configuration. Experiments were performed in which the reactor was operated at temperatures between 400°C and 550°C using different carrier gas flow rates, to determine the optimal conditions needed to produce bio-oil rich in CCA-metals. Mass balances were performed by evaluating the concentrations of the metals in each pyrolysis product using ICP-AES analysis. This paper discusses the lab-scale pyrolysis system, characterization of the CCA-treated wood waste, results of the optimization experiments, and details of on-going research.