Sunday, May 3, 2009
3-84
LHW pretreatment and enzymatic hydrolysis of rapeseed straw
Rapeseed cultivation is deserving a growing interest because rapeseed oil can be used for biodiesel production, adding interesting features (e.g. freezing point) for biodiesel to comply with EN 14214 quality norm. After seed harvesting, rape straw is left in the fields and usually eliminated by burning. Rapeseed straw is a lignocellulosic material containing on average 33% cellulose and 22% hemicelluloses (dry basis). This work examines the possibilities of using rapeseed straw as feedstock for fuel ethanol production. The raw material was submitted to Liquid Hot Water pre-treatment. The pretreated solid was further submitted to enzymatic hydrolysis, while the liquid fraction issued from pre-treatment was analyzed for sugar composition. A 22 factorial design was used to evaluate the influence of temperature (170-210ºC ) and time of pre-treatment (10-50 min) on the measured responses. Following first trials results, a composite central design was performed and response surface methodology was applied to determine the optimal operation conditions for either maximum glucose enzymatic yield or maximum xylose recovery in the liquid fraction. The maximum glucose recovery in the pretreated solid (68.3% of that in the raw material) resulted at 213.5 ºC and 42.4 min. If the glucose released by enzymatic hydrolysis together with the xylose recovery in the liquid is chosen as optimum condition, the best result was found at 191 ºC and 34 min, corresponding to 62.5% glucose yield, while sugars in the liquid fraction were 5.5 and 42.3% of the glucose and xylose present in the raw material, respectively.
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