Ethanol Production From Steam-Explosion Pretreated Wheat Straw IGNACIO BALLESTEROS, M a JOSÉ NEGRO, JOSÉ MIGUEL OLIVA, ARACELI CABAÑAS, P ALOMA MANZANARES,* AND MERCEDES BALLESTEROS CIEMA T-Renewable Energies Division, Av. Complutense, 22, 28040-Madrid-Spain; E-mail: p.manzanares@ciemat.es Abstract Bioconversion of cereal straw to bioethanol is becoming an attractive alternative to conventional fuel ethanol production from grains. In this work, the best operational conditions for steam-explosion pretreatment of wheat straw for ethanol production by a simultaneous saccharification and fermentation process were studied, using diluted acid [H 2 SO 4 0.9 % (w/w)] and water as preimpregnation agents. Acid- or water-impregnated biomass was steam-exploded at different temperatures (160–200°C) and residence times (5, 10, and 20 min). Composition of solid and filtrate obtained after pretreatment, enzymatic digestibility and ethanol production of pretreated wheat straw at different experimental conditions was analyzed. The best pretreatment conditions to obtain high conversion yield to ethanol (approx 80% of theoretical) of cellulose-rich residue after steam-explosion were 190°C and 10 min or 200°C and 5 min, in acid-impregnated straw. However, 180°C for 10 min in acid-impregnated biomass provided the highest ethanol yield referred to raw material (140 L/t wheat straw), and sugars recovery yield in the filtrate (300 g/kg wheat straw). Index Entries: Wheat straw; ethanol; diluted acid pretreatment; steam- explosion. Introduction During the past century , world energy consumption has mostly depended on the utilization of fossil fuels, which has led to harmful changes in our climate and increased the amount of greenhouse gases in the atmosphere. According to the World energy, technology and climate policy outlook report published in 2003 by the European Union (1), given the continued dominance of fossil fuels, world CO 2 emissions are expected to increase more rapidly than the energy consumption (2.1%/yr on an average). In 2030, world CO 2 emissions are expected to be more than twice the level of 1990. This scenario is a clear encouragement for developing Applied Biochemistry and Biotechnology 496 Vol. 129–132, 2006 Copyright © 2006 by Humana Press Inc. All rights of any nature whatsoever reserved. 0273-2289/06/129–132/496–508/$30.00 *Author to whom all correspondence and reprint requests should be addressed.