8-08: Overcoming the recalcitrance of softwood, hardwood and grass by ionic liquid and dilute acid pretreatment

Pretreatment of lignocellulosic biomass is an essential step for biofuel production via biological routes. In this study, three energy crops (pine, eucalyptus and switchgrass) were evaluated for their potential to be used as feedstocks for fermentable sugar production via ionic liquid and dilute acid pretreatments and enzymatic hydrolysis. The mechanisms of how these two pretreatment techniques disrupt the cell-wall matrix and break down lignin was investigated using Fourier Transform Infrared and Raman spectroscopy at the molecular level. Results show that the three feedstocks respond differently to the two pretreatment techniques. Significantly enhanced saccharification kinetics and sugar recovery is observed for all three feedstocks treated with ionic liquid. Among the three feedstocks, switchgrass has the highest sugar yield and fastest hydrolysis rates after both dilute acid and ionic liquid pretreatment. Of the two wood species, eucalyptus has higher and faster sugar recovery after ionic liquid pretreatment than pine. Dilute acid pretreatment does not have a significant enhancement effect on the saccharification of pine and eucalyptus. Spectroscopy indicates that lignin depolymerization induced by the two pretreatment techniques varies as a function of feedstock type, which may contribute to the observed variance in saccharification yields and rates. These results indicate that ionic liquid pretreatment works effectively on wide range of feedstocks, and may offer unique advantages over comparative pretreatment technologies.