Journal of Hazardous Materials 178 (2010) 604–611 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Environmentally friendly wood preservatives formulated with enzymatic-hydrolyzed okara, copper and/or boron salts Sye Hee Ahn a , Sei Chang Oh a , In-gyu Choi b , Gyu-seong Han c , Han-seob Jeong b , Ki-woo Kim d , Young-ho Yoon e , In Yang f,∗ a Department of Forest Resources, Daegu University, Gyeongsan 712-714, South Korea b Department of Forest Sciences, Seoul National University, Seoul 151-921, South Korea c Department of Wood and Paper Sciences, Chungbuk National University, Cheongju 361-763, South Korea d National Instrumentation Center for Environmental Management, Seoul National University, Seoul 151-921, South Korea e KCI Co. Ltd., Seosan, Chungcheongnam-do 356-874, South Korea f Research Institute for Agriculture and Life Sciences, Seoul National University, San 56-1 Sillim-Dong, Kwanak-gu, Seoul 151-921, South Korea article info Article history: Received 30 December 2009 Received in revised form 25 January 2010 Accepted 25 January 2010 Available online 1 February 2010 Keywords: Okara Wood preservatives Leachability Treatability Decay resistance SEM-EDX abstract Novel biocides, such as copper azole (CuAz) and ammoniacal copper quaternary (ACQ), are extensively used as substitutes for chromate copper arsenate (CCA) in wood preservation. However, the expense of these biocides has necessitated the development of cost-effective and environmentally friendly wood preservatives. This study was conducted to investigate the effectiveness against decaying fungi of the preservatives formulated with enzymatic-hydrolyzed okara (OK), which is an organic waste produced from the manufacture of tofu, CuCl 2 (CC) and/or Na 2 B 4 O 7 ·10H 2 O (B). With the addition of NH 4 OH as a dissociating agent, the addition of OK facilitated the target retention of most of the OK/CC and OK/CC/B preservative formulations in wood blocks. The OK-based wood preservatives (OK-WPs) were stable against hot-water leaching. When compared with control and CC-treated wood blocks, the leached wood blocks treated with OK/CC and OK/CC/B formulations showed excellent decay resistance against both Pos- tia placenta and Gloeophyllum trabeum, especially when OK was hydrolyzed by Celluclast at a loading level of 0.1 ml/g. Scanning electron microscopy (SEM) and SEM-energy dispersive X-ray (SEM-EDX) spectrome- try analyses demonstrated that preservative complexes, such as OK–CC and OK–CC–B, existed in the wood blocks treated with OK/CC and OK/CC/B formulations. This study results support the potential application of OK-WPs as environmentally friendly wood preservatives capable of replacing CuAz and ACQ. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The toxicity of chromium and arsenate elements, which are released from chromated copper arsenate (CCA)-treated wood, against human health and the environment has generated a lot of controversy [1–4]. As a result, the use of CCA-treated wood for residential purposes was prohibited by the United States Envi- ronmental Protection Agency, but CCA is still extensively used to protect wood for outdoor uses [5]. Additionally, when CCA-treated wood is removed from service, its disposal can cause serious envi- ronmental problems because it retains high levels of toxic elements. Humar et al. [6] predicted that the volume of the CCA-treated waste wood would be 16 million m 3 in 2020. Therefore, consider- able attention has recently been focused on the development of environmentally friendly, alternative wood preservatives to CCA. ∗ Corresponding author. Tel.: +82 2 880 4795; fax: +82 2 873 2318. E-mail address: dahadad2000@yahoo.com (I. Yang). The wood preserving industry has been engaged in several efforts to manufacture effective wood preservatives that are envi- ronmentally more acceptable. Consequently, novel biocides, such as copper azole (CuAz) and ammoniacal copper quaternary (ACQ), have become a predominant choice worldwide in today’s wood preservation systems from the end of the 1990s [7]. However, due to the high cost of these biocides compared to CCA, several researchers have investigated the development of new effective and economically practicable, preservation systems. For example, natural resources, such as egg albumin, milk casein [8] and soy pro- tein products [9,10], and industrial wastes, such as lignin [11,12] and tannin [13], were used as a raw material in their preservative formulations, because these resources are readily available in large quantities with preservative complexes retained from aqueous solutions, and might have a potential as inexpensive adsorbents. However, in Korea, such resources are unsuitable as ingredients in newly developed preservation systems because of their high cost or rarity. Okara (OK) is the residue generated as a byproduct dur- ing soymilk and tofu production. In Korea, approximately 0304-3894/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2010.01.128