(167f) Comparing Maximum Overall Pretreatment and Enzymatic Hydrolysis Sugar Yields from Poplar Wood Following THF Co-Solvent Enhanced Lignocellulosic Fractionation (CELF), Dilute Acid, and Organosolv Pretreatments

Because lignocellulosic ethanol production typically requires a costly pretreatment step to overcome biomass recalcitrance, advanced pretreatments could lead to significant reductions in overall ethanol production costs. The University of California at Riverside recently invented a novel pretreatment we now call Co-solvent Enhanced Lignocellulosic Fractionation (CELF) pretreatment that uses tetrahydrofuran (THF) in a homogeneous solution with water containing dilute sulfuric acid to achieve very high recovery of hemicellulose sugars in solution and removal of lignin during the CELF process.  Furthermore, the highly glucan enriched solids produced by CELF can be readily digested to high glucose yields with much lower and more economically attractive enzyme loadings than typical for most pretreatments.  This study optimized CELF pretreatment of poplar wood to maximize total xylose and glucose yields from the combined operations of pretreatment and subsequent enzymatic hydrolysis and compared the results to maximum total sugar yields from dilute acid and ethanol organosolv pretreatments of the same substrate. CELF pretreatment conditions that achieved the highest combined total sugar yields from poplar wood at high enzyme loadings were determined to be 160°C for 15 minutes with 0.5% H₂SO₄ as the catalyst at a 1:1 THF/H₂O ratio.  At these conditions, CELF removed more than 90% of the lignin from poplar and realized xylose plus glucose yields of more than 95% at low enzyme dosage.  Yield data will be presented over a range of enzyme loadings from 2 to 60 mg/g for CELF pretreatment compared to optimized application of dilute acid and ethanol organosolv pretreatments to the same poplar material.  In addition, composition analysis, SEM imaging, and other characterization tools will be employed to identify key differences in pretreated solids features that could be responsible for differences in sugar yields, particularly at lower enzyme loadings.