(412e) Scale-Up Evaluation of Ionic Liquid Based Sugar Production At High Solid Loading

Ionic liquid (IL) pretreatment is receiving significant attention as a potential process that enables fractionation of lignocellulose and produces high yields of fermentable sugars suitable for the production of renewable fuels. However, successful optimization and scale up of IL pretreatment involves challenges, such as high solids loading, biomass handling and transfer, washing of pretreated solids and formation of inhibitors, which are not addressed during the development stages at the small scale in a laboratory environment. As a first in the research 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 biofuels enabling technologies, have performed benchmark studies to resolve key challenges associated with IL pretreatment using 1-ethyl-3-methylimidazolium acetate and subsequent enzymatic saccharification beyond bench scale.

Using switchgrass, eucalyptus and mixture of both as feedstocks, we have successfully executed 600-fold, relative to the bench scale (6L vs 0.01L), scale-up of IL pretreatment and 60-fold (1.5L vs 0.025L) scale up of subsequent enzymatic saccharification at 15% (w/w) biomass loading. The results generated are consistent with those from the small-scale experiments that have been conducted at JBEI and elsewhere, and indicate there are no fundamental issues in terms of performance associated with the scale-up of an IL-based conversion technology. High solids loading during pretreatment and enzymatic hydrolysis offers several industrial advantages, including decreased reactor size, increased sugar titer and hydrolysis rate, and decreased water consumptions, but also disadvantage such as mass transfer limitations caused by high material viscosity, which needs process optimization. Clear enzymatic inhibition was observed when pretreated materials were not washed completely prior to hydrolysis, and thus, the inhibitors generated during pretreatment and washing can persist into hydrolysis and the downstream steps. As a result, optimization and engineering of the enzyme cocktail and design/operation of the pretreatment and post separation system must be realized before a commercially viable process is realized. The knowledge gained from this initial scale-up study is an essential first step in demonstrating the commercial viability of this promising pretreatment technology.