Production of Concentrated Monosaccharride Solutions From Biomass Using CO2-H2O Mixtures At Varying Temperatures

Wednesday, October 19, 2011: 3:15 PM
211 B (Minneapolis Convention Center)
Jeremy S. Luterbacher1, Jefferson W. Tester1 and Larry P. Walker2, (1)Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, (2)Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY

Sustainably producing concentrated solutions of monosaccharrides from biomass is a key bottleneck in the conversion of lignocellulosic biomass to biofuels or bioproducts. Most pretreatment and enzymatic hydrolysis processes are run at low-solid concentration (<10 wt%) and use chemical catalysts, while high-solids enzymatic hydrolysis experiments are almost always performed with air-dried pretreatment mixtures.

This study uses a stirred 1 L reactor to study high solids (40 wt%) and high-pressure (200 bar) H2O-CO2 pretreatment of mixed hardwood and switchgrass. In addition, two-temperature stage pretreatment was introduced and optimized to take advantage of the temperature dependent biomass depolymerization reaction sequence (a short high-temperature stage at 200-210ºC for 0 to 24 min was followed by a long low-temperature stage at 160-170ºC for 60 min). Optimal glucan to glucose yields around 80% were obtained after 72 hrs of dilute hydrolysis (1 wt% glucan) for both substrates at similar pretreatment conditions (210ºC, 16 min for hardwood and 210ºC, 1 min for switchgrass, both followed by 60 min at 160ºC). These optimally pretreated substrates were used as feedstock in high-solids enzymatic hydrolysis reactions, which gave glucose yields above 80% for both hardwood and switchgrass after 48 hrs of hydrolysis. Therefore, without additional chemical catalysts or any drying, two-temperature stage H2O-CO2 pretreatment coupled with high-solids enzymatic hydrolysis can produce monosaccharide solutions of 185 gr/L (170 gr/L of glucose and cellobiose 15gr/L of hemicellulose sugars) for mixed hardwood and 148 gr/L (115 gr/L of glucose and cellobiose 33gr/L of hemicellulose sugars) for switchgrass. This suggests that H2O-CO2 pretreatment is an attractive alternative to chemically catalyzed processes such as dilute acid pretreatment.

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