title: Impact of high biomass loading on ionic liquid pretreatment.
abstract: BACKGROUND
  Ionic liquid (IL) pretreatment has shown great potential as a novel pretreatment technology with high sugar yields. To improve process economics of pretreatment, higher biomass loading is desirable. The goal of this work is to establish, the impact of high biomass loading of switchgrass on IL pretreatment in terms of viscosity, cellulose crystallinity, chemical composition, saccharification kinetics, and sugar yield.
  
  
  RESULTS
  The pretreated switchgrass/IL slurries show frequency dependent shear thinning behavior. The switchgrass/IL slurries show a crossover from viscous behavior at 3 wt% to elastic behavior at 10 wt%. The relative glucan content of the recovered solid samples is observed to decrease with increasing levels of lignin and hemicelluloses with increased biomass loading. The IL pretreatment led to a transformation of cellulose crystalline structure from I to II for 3, 10, 20 and 30 wt% samples, while a mostly amorphous structure was found for 40 and 50 wt% samples.
  
  
  CONCLUSIONS
  IL pretreatment effectively reduced the biomass recalcitrance at loadings as high as 50 wt%. Increased shear viscosity and a transition from 'fluid' like to 'solid' like behavior was observed with increased biomass loading. At high biomass loadings shear stress produced shear thinning behavior and a reduction in viscosity by two orders of magnitude, thereby reducing the complex viscosity to values similar to lower loadings. The rheological properties and sugar yields indicate that 10 to 50 wt% may be a reasonable and desirable target for IL pretreatment under certain operating conditions.
authors.affiliation: Deconstruction Division, Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley CA, USA. seesing@sandia.gov.
authors.forename: Alejandro G
authors.initials: AG
authors.lastname: Cruz
authors.forename: Chessa
authors.initials: C
authors.lastname: Scullin
authors.forename: Chen
authors.initials: C
authors.lastname: Mu
authors.forename: Gang
authors.initials: G
authors.lastname: Cheng
authors.forename: Vitalie
authors.initials: V
authors.lastname: Stavila
authors.forename: Patanjali
authors.initials: P
authors.lastname: Varanasi
authors.forename: Dongyan
authors.initials: D
authors.lastname: Xu
authors.forename: Jeff
authors.initials: J
authors.lastname: Mentel
authors.forename: Yi-De
authors.initials: YD
authors.lastname: Chuang
authors.forename: Blake A
authors.initials: BA
authors.lastname: Simmons
authors.forename: Seema
authors.initials: S
authors.lastname: Singh