Pre-processing of lignocellulosic biomass; the way to improve the overall biomass to sugar conversion, technical feasibility and environmental impacts

The role of physical and chemical characteristics of biomass has been extensively studied in relations to production of sugars and other products. Equally important, however, is the role of biomass pre-processing prior to pretreatment in the improvement of the overall products yield. How can we pre-process biomass to provide the maximum yield of hydrolysable and fermentable sugars from lignocellulosics?

In this presentation we discuss how pre-processing of biomass by a) increasing the moisture content (MC) prior to pretreatment and b) mixing biomass during pretreatment can increase the overall sugar recovery in hydrolysable and fermentable form. During steam pretreatment and enzymatic hydrolysis of poplar with moisture contents of 0, 10, 35 and 50%, there was a significant increase (up to 29%) in hydrolysability of chips when comparing conversion of low MC chips with those that had greater than 35% MC. Increasing the moisture content of the dried chips prior to pretreatment resulted in an “evening out” of hydrolysis yields, with all of the pretreated substrates exhibiting the same hydrolysis yields regardless of their initial moisture content.

We will also present results that show that by mixing wheat straw and poplar at various ratios during steam pretreatment of 195^oC, 5 minutes and 3% SO_2, we can increase the glucose and xylose yield by 14 and 23%, respectively compared to 100% poplar. Finally, we will compare the environmental impacts of using single feedstock (100% poplar) with mixed biomass (poplar and wheat straw) during pretreatment and enzymatic hydrolysis using Life Cycle Assessments (LCA).