Second generation bioethanol from steam exploded Eucalyptus globulus wood

Second generation ethanol was obtained from steam exploded Eucalyptus globulus. The wood was subjected to steam explosion without external catalyst addition, in order to alter the feedstock structure and to solubilise the hemicellulosic fraction. The experimental work was carried out at severities (So) in the range 3.52-4.83, and the treated solids were subjected to enzymatic hydrolysis. The effects of temperature (°C) and processing time (min) on the sugar yield (glucose and xylose) obtained in enzymatic hydrolysis and on the kinetic parameters describing the saccharification were measured. In most of experiments, cellulose was almost quantitatively retained in solid phase. Autohydrolysis experiments performed under selected conditions (195 °C and 34 min) enabled the recovery of 18.1 g sugars/100 g oven-dry raw material in liquor, and led to spent solids highly susceptible to enzymatic hydrolysis (for which cellulose conversions up to 99.5% were reached). Simultaneous Saccharification and Fermentation of solids from selected autohydrolysis experiments led to media containing 51 g ethanol/L (corresponding to 91% cellulose conversion into ethanol).