10-30: Effects of Hardwood Mixtures on Xylose and Glucose Yields during Dilute Acid Pretreatment and Enzymatic Hydrolysis

Real-life forestry harvesting scenarios will dictate that forestry feedstock will come as a mixture of multiple biomass species present in the forest. Moreover, bark biomass, which is an integrated part of the tree, will probably be part of that mixture. This work used sweetgum wood, oak wood, oak bark, and sweetgum bark to investigate the effect of mixing biomasses on xylose and glucose yields, as well as developing a model to predict sugar yields ensuing from mixed biomass samples during dilute acid pretreatment and enzymatic hydrolysis. Pretreatment with 0.98% (v/v) H₂SO₄ at 160°C for 20 min followed by cellulose hydrolysis yielded carbohydrate recoveries for pure samples and samples consisting of 70% sweetgum wood mixed with: 1) 30% sweetgum bark; 2) 30% oak bark; or 3) 30% oak wood. Results showed that xylose and glucose yields were species and plant-part dependent. Oak wood yielded 35% of its theoretical xylose content, whereas sweetgum wood yielded 65%. However, both bark species were resistant to enzymatic hydrolysis. With 100% sweetgum wood as experiment control, statistical analysis of data demonstrated that addition of oak bark and wood to sweetgum wood did not have a significant effect (P > 0.05) on xylose and glucose recoveries. Significantly higher concentration of xylose observed with addition of sweetgum bark to sweetgum wood indicated synergetic interactions between them during pretreatment. Finally, addition of weighted sugar yields from pure biomass was a valid method to predict sugar yields produced by mixed samples, except for xylose from sweetgum wood and bark combination.