Optimization of rice husk pretreatment using Box-Behnken design (BBD) Teck Nam Ang a , Gek Cheng Ngoh a* and Adeline Seak May Chua a a Department of Chemical Engineering, Faculty of Engineering University of Malaya, 50603 Kuala Lumpur, Malaysia * Corresponding Author’s E-mail: ngoh@um.edu.my Keywords: Rice husk; Optimization; Pretreatment; Response surface methodology (RSM); Box- Behnken design (BBD). Extended Abstract Rice husk, the by-product of rice milling industry, is a widely available lignocellulosic biomass. In Asia-Pacific region alone, approximately 43.2 metric tonnes of rice husk per year is generated along with the production of rice (FAOSTAT 2010; Hashim et al. 1996). This lignocellulosic agricultural by-product has relatively high cellulose content, and the application of this alternative raw material could improve the process economy of industrial bioprocesses. Nevertheless, direct utilization of rice husk gives low bioconversion yield. Therefore, pretreatment is necessary to disrupt its recalcitrant structure prior to the biomass conversion. Till date, there is no specific pretreatment reagent reported particularly effective in pretreating rice husk. In general, acid and alkali are used in the pretreatment of the biomass. A preliminary study was conducted in this work to screen the effect of various acids and alkalis in the pretreatment of rice husk. The amount of total reducing sugars (TRS) released into the hydrolysate reflects the effect of each pretreatment reagent on rice husk (Figure 1). Acid pretreatments yielded higher TRS than the alkali pretreatments with the highest TRS content achieved by hydrochloric acid (HCl) pretreatment (15.04 ± 0.63 mg/ml), followed by nitric acid (HNO 3 ) and sulphuric acid (H 2 SO 4 ) with 12.20 ± 0.13 and 7.22 ± 0.27 mg/ml TRS, respectively. Meanwhile, the alkali pretreatments yielded less than 1 mg/ml TRS as the pretreatment reagents mainly delignifying rice husk rather than resulting in extensive hydrolysis of cellulose (Brannvall 2004; Weil et al. 1994). The findings obtained indicating HCl pretreatment has the greatest effect on rice husk. Hence, an optimization study on the pretreatment of rice husk by HCl was performed using Box-Behnken design (BBD) to evaluate the optimum operating condition for achieving the desirable TRS release. Figure 1: The effects of various pretreatment reagents on rice husk. In the optimization of HCl pretreatment, the effects of HCl loading (0.25 – 1.25%, w/v), pretreatment duration (1 – 3 hours), and pretreatment temperature (100 – 140 o C) were investigated. The effects of all model terms were analyzed with ANOVA using Design-Expert Version 6.0.6 (Stat- Ease Inc., Minneapolis). A quadratic model was selected to fit the responses, and the proposed model was statistically significant with insignificant lack of fit. Having had the insignificant terms removed, the reduced quadratic model is shown in Equation (1), where Y represents TRS as a function of HCl loading (X 1 ), pretreatment duration (X 2 ), and pretreatment temperature (X 3 ). Proc. of the 14 th Asia Pacific Confederation of Chemical Engineering Congress Editors: Chi-Hwa Wang, Xin Wang and Praveen Linga. Copyright © 2012 APCChE Organisers. All rights reserved. Published by: Research Publishing ISBN: 978-981-07-1445-1 doi:10.3850/978-981-07-1445-1 211 669