Tuesday, April 30, 2013
Exhibit Hall
Forest residues represent the most cost effective feedstock for biorefinery based on a recent report by the National Academy of Sciences. However, forest residues contain a significant amount of bark therefore has a very high lignin content, especially for softwood forest residues. The high lignin content is a significant challenge for bioconversion through the sugar platform. This study investigates the potential of using forest residues of Doulas-fir for sugar production using SPORL pretreatment. The optimized pretreatment conditions were: sulfuric acid dose 0.4 mL/L total liquor; sodium bisulfite 12% (w/w); cooking temperature165˚C; and cooking time 75 minutes. The sugars yield of the pretreated substrates is promising (i.e. 88% conversion) at low cellulase doses (i.e. 7.5 FPU/g dry mass). This yield is comparable to similar process using clean wood pulp chips feedstock. Comparing to clean chips, however, the forest residues contain higher amount of fine particles (i.e. approximately 30% of the mass are smaller than 95mm in diameter) and barks (i.e. 8~15%). Furthermore, the concentrations of the fermentation inhibitors were higher in the pretreatment spent liquor (i.e. hydroxymethylfurfural 3.9mg/mL and furfural 5.7mg/mL), which can be due to the uneven particle size distribution and varying chemical compositions of different size fractions in the feedstock. The arabinan content, for example, is particular higher in barks than in the cleaned chips, and the bark content is higher in the smaller particles. More detailed investigation on the physical/chemical characteristics of forest residues and their effects on recalcitrance to bioconversion will be presented.