Proceedings of SEEP2016, 22-25September 2016, Kayseri 36 FREEZING PRETREATMENT OF LIGNOCELLULOSIC MATERIAL: A CHEAP ALTERNATIVE FOR NORDIC COUNTRIES Vahur Rooni 1 , Merlin Raud 2 , and Timo Kikas 3 1 Estonian University of Life Sciences, Institute of Technology, Tartu; email: vahur.rooni@student.emu.ee 2 Estonian University of Life Sciences, Institute of Technology, Tartu; email: merlin.raud@.emu.ee 3 Estonian University of Life Sciences, Institute of Technology, Tartu; 1. email: timo.kikas@.emu.ee Abstract Using lignocellulosic biomass as an alternative transportation fuel resource is attractive due to its abundance and low cost. Conventional pretreatment methods such as steam explosion or ammonia fibre expansion need technically complex devices, high energy input and the use of toxic chemicals in order to achieve high glucose and ethanol yields. In this paper freezing pretreatment of barley straw was investigated as a low energy input and cost effective alternative pretreatment method for second generation bioethanol production. Laboratory and field tests were conducted. In the freezing pretreatment method milled biomass mixed with water was frozen up to -18°C for a certain period of time. The frozen biomass was then defrosted to room temperature (ca. 22°C). The freezing cycles were repeated several times to study the effect of repeated freezing. In addition, field experiments were carried out by taking samples of barley straw that was stored outside both in bales and swaths during a time period from September to March of two consecutive years (in winter 2014 to 2015 and 2015 to 2016). Freezing pretreatment was followed by enzymatic hydrolysis and fermentation. Glucose and ethanol concentrations were used as indicators of pretreatment efficiency. The highest hydrolysis efficiency of 30.37% was achieved in the laboratory tests where biomass was frozen and thawed six times. The best result from a field test was 2.56% from straw stored as swath and gathered in March. Fermentation yields ranged up to 66.37 g/kg. Field tests show that in the bale the temperature never fell below freezing and thus, the pretreatment was not effective. In the swath the straw does freeze through but the winter in Estonia was too mild for this method to work effectively. Keywords: bioethanol, lignocellulosic biomass, biofuel, freezing pre-treatment. INTRODUCTION Lignocellulosic biomass has been widely used as an energy source for a long time. Most commonly it is used for heat and electricity production by burning it directly. Yet, most of the primary energy (up to 80%) consumed worldwide today is produced from fossil fuels. From this 58% is used for the transportation sector alone [1]. Demand for energy rises daily and therefore, new, cheap and sustainable alternatives for liquid fuel production are needed. At the moment biofuels are considered to be the most favourable choice due to their abundance, renewability, biodegradability and cost- effectiveness [1–3]. Global bioethanol production in 2015 was 98.3 billion litres, majority of which was first generation bioethanol, produced from food crops such as sugar cane, maize, etc. [4]. Thus, a new and cheap alternative has to be found to prevent food crops usage as fuel production feedstock. Plants consist primarily of plant cell walls from which about 75% are different polysaccharides, which can be used for ethanol production with right conversion treatment [5]. Therefore, lignocellulosic