(793f) Measuring Free Water Content and Pore-Size Distribution of Biomass

Authors: 
Lischeske, J. J., National Renewable Energy Laboratory
Nelson, R. S., National Bioenergy Center, National Renewable Energy Laboratory
Stickel, J. J., National Renewable Energy Laboratory



Conducting unit operations such as pretreatment and enzymatic hydrolysis at high-solids loading offers economic advantages, but presents challenges in characterizing the flow and kinetics inside reactor vessels. An important factor in predicting the rheology of biomass slurries is their free water content. While this is typically estimated by the total water content, biomasses may have different water-retention properties based on their distinct structures, which in turn are affected by their physical and chemical treatment histories. Two orthogonal benchtop methods are presented for measuring free water content of biomass slurries. One uses centrifuge dewatering, which removes water not bound to the surface of the biomass particles. The other relies on solute exclusion of a macro-molecular tracer, while accounting for adsorption phenomena, to measure water external to biomass particles. These methods provide different and complimentary means to determining biomass slurry free water content.

Additionally, there has been significant interest in the effect of porosity and enzyme accessibility on reaction kinetics. Therefore, the solute exclusion method was extended to study porosity distributions of pretreated biomass. Taken together, the ability to measure both free water content of biomass slurries and pore-size distribution of biomass particles provides a basis for investigating flow properties and reaction kinetics in high-solids reactor systems.

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