Rheological Characterization of Liquefaction Processing Effect on Corn Stover Biomass Slurries

Second-generation biofuels are being developed from non-food plant resources to address the socio-economic concerns derived from first-generation biofuels of food and land competition. However, second-generation biofuel processing confronts many processing challenges with high yield stresses at economically necessary solids loadings (>20wt.%). Various liquefaction techniques are employed to convert sugars from corn stover biomass slurries, which directly impact the rheological response through lowering solids concentrations and altering particle properties. In this study, the flow response of corn stover biomass slurries processed by enzyme liquefaction and dilute acid pretreatment are explored using a wide-gap geometry rheometer. Flow curve experiments reveal that yield stress is a function of solids loading and enzyme liquefaction further reduces the yield stress by reducing the total insoluble solids within the slurry. Combined dilute acid pretreatment and enzyme liquefaction reduce static yield stress and particle size. Drying and fractionating of particles from slurries reveal that larger particles produce a larger shear stress response than smaller particles. For successful processing on a large scale, maximizing the initial solids loading and minimizing the yield stress and viscosity of corn stover biomass slurries are essential.