10-41: Resolving Process Scale-Up Issues of Ionic Liquid Pretreatment and Saccharification of Biomass to Monomeric Sugars

The successful optimization of biomass processing challenges such as mixing, biomass handling and transfer, recirculation of water during washing of pretreated solids, and uniform enzyme loading and dosage are critical to large scale (LS) application of biomass conversion pathways. Scaling of these factors is not usually addressed during the development stages at the small scale (SS) in a laboratory environment. As a first in the community, the Joint BioEnergy Institute (JBEI), in collaboration with the Advanced Biofuels Process Development Unit (ABPDU), a DOE-funded facility that supports academic and industrial entities in scaling their novel technologies, have performed benchmark studies to resolve these key LS process issues associated with ionic liquid (IL) pretreatment and subsequent saccharification.

We executed 600 and 150-fold scale-up of IL pretreatment (6L) and saccharification (1.5L), respectively, from the laboratory scale of operations at JBEI. Switchgrass, eucalyptus, and mixed feedstocks were processed at 10 and 15%w/w, 1 and 3h, and 120 and 160°C. Shear mixing at LS caused high lignin removal (LS: 74.2 vs. SS: 79.2%), xylan recovery (38.3 vs. 11.9%), and glucose yields with faster enzymatic kinetics (86.7% at 24h). Rheological properties indicate that pretreated switchgrass (G*=1.2X10³ Pa; δ=30.9°) has reduced resistance to flow compared to pretreated eucalyptus (G*=2.3X10⁵ Pa; δ=19.6°). Energy balance based on energy density measurements on bomb calorimeter showed 45% (J/J) energy recovery in sugar-rich liquors. The results indicate that IL-based conversion technology can be effectively scaled to larger operations, and the results establish the first scaling parameters for this innovative biomass conversion pathway.