COMPARISON OF SO2 AND H2SO4 IMPREGNATION OF SOFTWOOD PRIOR TO STEAM PRETREATMENT ON ETHANOL-PRODUCTION

The pretreatment of softwood with sulfuric acid impregnation in the pr oduction of ethanol, based on enzymatic hydrolysis, has been investiga ted. The parameters investigated were: H2SO4 concentration (0.5-4.4% w /w liquid), temperature (180-240 degrees C), and residence time (1-20 minutes). The combined severity (log Ro-pH) was used to combine the pa rameters into a single reaction ordinate. The highest yields of fermen table sugars, i.e., glucose and mannose, were obtained at a combined s everity of 3. At this severity, however, the fermentability declined a nd the ethanol yield decreased. In a comparison with previous results, SO2 impregnation was found to be preferable, since it resulted in app roximately the same sugar yields, but better fermentability.