13-17: Combined silage and hydrothermal pretreatment of wheat straw

Biomass ensiling is a well known method for crop preservation to provide nutrient rich animal feed all year around. Ensiling is an anaerobic fermentation dominated by lactic acid bacteria (LAB) that produce organic acids, decreasing pH, thus inhibiting growth of fungi, yeasts and bacteria that decompose the carbohydrate structure. At present, silage is mainly used as animal feed; however, it has received increased attention as storage and pretreatment method for bio-refineries and bio-fuel production in recent years.

Within the past decade many pretreatment methods have been applied for treatment of lignocellulosic biomass prior to an enzymatic hydrolysis and fermentation. DTU has been involved in developing hydrothermal pretreatment where it is possible to handle biomass at high dry matter contents (30-40 %) based solely on steam application without addition of chemicals. This process is performed at high temperatures (˂180°C). Our preliminary experiments showed that ensiling as a stand-alone pretreatment is not severe enough to break down lignocellulosic structure of wheat straw, however in combination with hydrothermal treatment it can serve as a “pre-pretreatment” method by providing organic acids that stimulate autohydrolysis which therefore decrease the requirements of high temperature in the hydrothermal treatment . In the frame of a collaborative project between Europe and Brazil the aim is to establish joint research on hydrothermal pretreatment on wheat straw and sugarcane bagasse. One of our tasks is to test ensiling as a biological pretreatment prior to hydrothermal pretreatment, by optimizing ensiling conditions.