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Poster Presentation 1-20
Combined Use of H2SO4 and SO2 Impregnation for Steam Pretreatment of Spruce for Ethanol Production
Johanna Söderström, Linda Pilcher, Mats Galbe, and Guido Zacchi Department of Chemical Engineering 1 Lund University P.O. Box 124, SE-221 00 Lund Sweden
Telephone: 46 46 222 82 97; Fax: 46 46 222 45 26; E-mail: guido.zacchi@kat.lth.se
Fuel ethanol can be produced from softwood through hydrolysis in an enzymatic process. Prior to enzymatic hydrolysis of the softwood, pretreatment is necessary. In this study two-step steam pretreatment by dilute H2SO4 impregnation in the first step and SO2 impregnation in the second step to improve the overall sugar and ethanol yield has been investigated. The first pretreatment step was performed under conditions of low severity (180ºC, 10 min, 0.5% H2SO4) to optimize the amount of hydrolysed hemicellulose. In the second step the washed solid material from the first pretreatment step was impregnated with SO2 and pretreated under conditions of higher severity to hydrolyze a portion of the cellulose, as well as to make the cellulose more accessible to enzymatic attack. A wide range of conditions was used to determine the most favourable combination. The temperatures investigated were between 190 and 230ºC, the residence times 2, 5 and 10 minutes and an SO2 concentration of 3%.
The effects of pretreatment were assessed by both enzymatic hydrolysis of the solids and with simultaneous saccharification and fermentation (SSF) of the whole slurry, after the second pretreatment step. For each set of pretreatment conditions the liquid fraction was fermented to determine any inhibiting effects. The ethanol yield using the SSF configuration reached 66% of the theoretical value for pretreatment conditions of 210ºC and 5 min. The sugar yield using the SHF configuration reached 71% for pretreatment conditions of 220ºC and 5 min. In an attempt to improve the yield further, extensive washing of the solid material after the first pretreatment step is presently performed to increase the uptake of SO2 in the impregnation for the second pretreatment step. The results from this study will be presented.
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