Increase of accessibility of mixed fruit waste for effective digestion Shouvik Saha, Mayur B. Kurade, Byong-Hun Jeon* Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul. 2. Contour response surface and 3D plots Introduction Agro-food industries discard enormous amounts of fruit and vegetable processing wastes (liquid and solid) into the environment (Panda et al., 2016; Wadhwa and Bakshi, 2013). The disposal of this large amount of wastes is correlated with the emission of greenhouse gases (GHG) such as methane (28–36 times more potent in atmospheric warming than carbon dioxide) (Chai et al., 2016). A proper waste management strategy in the form of anaerobic digestion could reduce the amount of material added to landfills. Pretreatment is the first step toward complete utilization of these valuable substrates in bioenergy production (Saha et al., 2016). Objectives Fig. Temperature with acid concentration (a. b), time with acid concentration (c, d) and time with temperature (e, f). Optimization of the acetic acid pretreatment conditions for mixed fruit wastes (FW) using Response Surface Methodology (RSM). Validation of sugar recovery through Fourier transform infrared spectroscopy (FTIR), Thermogravimetric (TG) and X-ray diffraction (XRD) analyses. Scanning electron microscopy (SEM) to confirm the cellular destruction and integrity lose in the pretreated FW. Comparative methane production between untreated and pretreated FW to confirm the effect of acetic acid pretreatment on FW bioavailability. 3. Validation of the sugar recovery Materials and Method Box-Behnken design summary Fig. FTIR (a) and TG (b) analyses of untreated and pretreated FW. 4. SEM observations Experimental design Fig. SEM observations of untreated and pretreated FW. 5. Methane production Results and Discussions 1. Response recovery of the fermentable sugars Fig. Cumulative methane production in pretreated and untreated FW. Conclusions Dilute Acetic acid (0.2 M, 62.5 °C, 30 minutes) pretreatment minimized the loss of sugar during pretreatment by achieving the maximum recovery (95.01%) of fermentable sugars, considering the carbohydrates (701.7 mg g-1) in the pretreated FW and the reducing sugars (21.92 mg g-1) in the hydrolysate. Acetic acid pretreatment also increased substrate vulnerability to microorganisms for better digestion. Higher methane yield (53.58 mL g-1 VSinitial) was obtained with pretreated FW, indicates improved accessibility during anaerobic digestion. Dilute acetic acid pretreatment of FW before anaerobic digestion will improve the performance of the digestion process on the industrial scale. Acknowledgement This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry, & Energy (MOTIE) of the Republic of Korea (No. 20163010092250), and a National Research Foundation of Korea (NRF) grant funded by the Korean government (MEST) (No. 2017R1A2B2004143). References Panda SK, Mishra SS, Kayitesi E, Ray RC, Microbial-processing of fruit and vegetable wastes for production of vital enzymes and organic acids: Biotechnology and scopes, Environ Res 146, (2016) 161-72. Wadhwa M, Bakshi MPS, Utilization of fruit and vegetable wastes as livestock feed and as substrates for generation of other value-added products, Editor: Makkar HPS, In: FAO; 2013. Chai X, Tonjes DJ, Mahajan D, Methane emissions as energy reservoir: Context, scope, causes and mitigation strategies, Prog Energy Combust Sci 2016;56:33-70. Saha S, Kurade MB, El-Dalatony MM, Chatterjee PK, Lee DS, Jeon B-H, Improving bioavailability of fruit wastes using organic acid: An exploratory study of biomass pretreatment for fermentation, Energy Convers Manage 127, (2016) 256-64.