Physical and mechanical properties of flakeboard produced from recycled CCA-treated wood

Chromated copper arsenate (CCA) treated wood has been most widely used in North America since the 1970s for many exterior applications such as decks, fences, playground equipment, utility poles, and others. A large volume of CCA-treated wood is currently coming out of service. Traditional disposal methods such as landfilling and incineration are not without adverse environmental outcomes. Recycling CCA-treated wood into composite products is one alternative to ease the disposal problem. In this study, the effects of different ratios of recycled CCA-treated wood and untreated virgin wood on flakeboard properties were compared. The mechanical, physical, and decay resistance properties of flakeboards manufactured fi-om five different ratios of recycled CCA-treated wood and untreated virgin southern pine wood were investigated. The ratios were 100:0,75:25,50:50,25:75, and 0: 100. The median ratio with 50 percent of CCA-treated wood and untreated wood was found to be the optimum combination. In this case, residual CCA level was sufficient enough to prevent substantial weight losses in the decay tests, but low enough so that panel mechanical and physical properties were not substantially reduced. Chmmated copper arsenate (CCA) has been widely used to treat exterior wood in North America for many uses, including decks, gazebos, playground equipment, landscape timbers, agricultural stakes, marinas, and utility poles. For the past two decades, CCA has emerged as the primary wood preservative for residential and commercial applications (Smith and Shiau 1998). Over 6 billion board feet (14.2 million m3) of lumber treated with CCA are produced mually in the United States (MicMewright 1998). When atreated woodproduct reaches the end of its service life, either through mechanical damage or failure, biological deterioration, or obsolescence, these products may be salvaged, abandoned in place, or removed from active service for disposal. Cooper (1993a) estimated that the future volumes of CCA-treated wood removed from service in the United States would rise from 1 million m3 in 1990 to 16 million m3 in 2020. The increasing volume of CCAtreated wood products coming out of service is posing disposal problems. Qpical waste disposal options such as landfilling or incineration are both generally regarded by the public as having negative environmental consequences. It should be noted that incineration can be done in a cement kiln with the proper controls. Nonetheless, both options are expensive. There are increasing public concerns and restrictions on disposal due to potential adverse effects on human health and the environment. Many scientists have studied various options to resolve these problems, including reuse, abatement, modification, recycling, retreatment, and destruction (Cooper 1993b, 1996). The recycling option is potentially economically feasible and definitely environmentally attractive; recycling into wood composite products can be regarded as the most viable option (Felton and DeGroot 1996, Cooper 1999). Moreover, the significant quantities of residual CCA content in the wood can still have preserving capability The authors are, respectively, Graduate Research Assistant, and Associate Professor, School of Renewable Natural Resources, Louisiana State Univ. Agricultural Center, Baton Rouge, LA 70803; Principal Wood Scientist, USDA Forest Serv., Southern Res. Sta., Pineville, LA 7 1360. This paper (0340-0976) is publishedwith the approval of the Director of the Louisiana Agricultural Expt. Sta. This paper was received for publication in August 2002. Article No. 9522. +Forest Products Society Member. @Forest Products Society 2004. Forest Prod. J. 54(2):89-94. FOREST PRODUCTS JOURNAL VOL. 54. NO. 2 Table 1. Experiment design -Treatment Ratil A flakes vs. untreated flakes