Organosolv pretreatment of biomass for biofuel and biorefinery applications
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- Institutt for kjemi 
The overall objective of this Master thesis was to establish an optimized ethanol organosolv pretreatment of Norway spruce (Picea abies) for bioethanol production (63 wt% EtOH, pH~3.5 in aqueous phase, 170-240 °C, 90 min) utilizing hydrolytic enzymes in the saccharification. Focus in the ethanol organosolv pretreatment was on achieving a high degree of delignification with minimal degradation of cellulose. To test the generality of the method, a series of ethanol organosolv pretreatments were also to be performed on sugarcane bagasse (50 wt% EtOH, pH~3.5 in aqueous phase, 155-210 °C, 90-120 min). The degree of delignification increased with increasing temperature during pretreatment, the fastest increase was observed with sugarcane bagasse. Two reactor modes were utilized in the pretreatment of Norway spruce. Still, the use of a regular batch reactor achieved the highest degree of delignification. The maximum degree of delignification of ~66% was reached at ~235 °C for Norway spruce, while sugarcane bagasse reached ~82% at ~210 °C. Cellulose was subjected to degradation (5-10 percentage points) at these temperatures. This was not desired. Sequential enzymatic hydrolysis (30 FPU/g cellulose, 32 pNPGU/g cellulose, 50 °C, 48 hrs) of ethanol organosolv pretreated biomass achieved complete conversion for both rawmaterials at the highest degrees of delignification. SEM analyses of the ethanol organosolv pretreated biomass indicated reprecipitation of spherical lignin particles on Norway spruce pretreated at high temperatures.