Proceedings of the 14 th International Conference on Environmental Science and Technology Rhodes, Greece, 3-5 September 2015 CEST2015_00080 LOW-TEMPERATURE THERMAL TREATMENT OF LIGNOCELLULOSIC WASTE PRIOR TO ANAEROBIC DIGESTION PELLERA F.M., ACHEILAS I. and GIDARAKOS E. School of Environmental Engineering, Technical University of Crete, Politechnioupolis, 73100 Chania, Greece E-mail: gidarako@mred.tuc.gr, fpellera@isc.tuc.gr ABSTRACT This study aims to determine the effect of low-temperature thermal pretreatment on two lignocellulosic materials originating from agroindustrial activities, namely grape marc and cotton gin waste. More specifically, this paper focuses on the impact of thermal pretreatment on the solubilization and the methane potential of these two materials. Thermal pretreatment was carried out by soaking the materials in deionized water at three different temperatures, i.e. 75, 50 and 100°C. The effect of pretreatment duration was investigated in the range of 30 – 240 min. Solubilization of the materials was determined by measuring soluble chemical oxygen demand (sCOD) and total phenols concentrations in the liquid phase obtained after pretreatment. The methane potential of the solid and liquid fractions was determined through Biochemical Methane Potential (BMP) assays. The samples used in these assays were chosen on the basis of the solubilization data after pretreatment. According to the results, pretreatment temperature affects solubilization more, compared to pretreatment duration. Methane production data indicated that pretreatment favored both release of biodegradable material in the liquid phase, and digestibility of remaining solids. Thermal pretreatment at 75 °C provided the highest SMY for what concerns GM-solid substrates and CGW-liquid substrates, while the best results for GM–liquid substrates and CGW-solid substrates were obtained after pretreatment at 100 °C. Keywords: anaerobic digestion, lignocellulosic, thermal, pretreatment, methane 1. Introduction Anaerobic digestion is a biological process which is widely used to treat complex organic substrates in order to produce biogas (Aragaw et al., 2013; Ariunbaatar et al., 2014). This technology can serve as a means of both sustainable waste management and alternative energy production (Bruni et al., 2010). In fact, in the last years the application of anaerobic digestion of solid substrates, particularly waste, has been intensively investigated (Ariunbaatar et al., 2014). Among the most studied solid substrates for anaerobic digestion are lignocellulosic biomass and waste. However, the effectiveness of such a process is often limited by the fact that these materials are recalcitrant to biodegradation due to their composition, consisting of cellulose, hemicellulose and lignin. For this reason, pretreatment is usually applied, aiming to enhance digestibility of lignocellulosic substrates. Pretreatment methods include physical, chemical and biological processes (Haghighi Mood et al., 2013; Hendriks and Zeeman, 2009). In the present study the effect of low-temperature (50–100 °C) thermal pretreatment on solubilization and methane potential of grape marc (GM) and cotton gin waste (CGW) was investigated, through batch hydrolysis experiments and Biochemical Methane Potential assays. 2. Materials and methods 2.1. Substrate and inoculum Grape marc (GM), comprising of red grape skins, seeds and stalks, was obtained from a local winery, while cotton gin waste (CGW) comprising of cotton fiber, stalks and leaves was obtained