(115c) Design of a Laboratory Scale Pyrolysis System for Evaluating the Recycle Potential of Cca-Treated Wood Waste

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

Pyrolysis, the heating of biomass at temperatures between 400°C and 650°C in the absence of oxygen, is a well studied technology that can be applied to CCA-impregnated wood waste. Pyrolysis of lignocellulosic material produces char, liquid condensate (bio-oil), and non-condensing gases. The focus of this research is on removing the CCA components from wood while recovering the energy value of the wood. This is accomplished by concentrating the CCA metals in the bio-oil, for possible re-use in wood preservatives, during pyrolysis. A 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. This paper discusses the process of designing the laboratory scale pyrolysis system and preliminary experimental results.