(192f) Towards a Cost-Competitive Ionic Liquid Based Pretreatment: Insights from Technoeconomic Analysis

In a traditional ionic liquid (IL) pretreatment process, IL is removed from pretreated biomass slurry to facilitate subsequent hydrolysis using commercial enzyme cocktails that are usually not IL-tolerant. The IL removal is commonly accomplished by washing pretreated biomass with water – in this study, we refer to this configuration as ‘water-wash (WW)’ route. The WW route has been widely used as it facilitated the early-stage development of biomass pretreatment technologies using solvents such as ILs. Based on our recent studies (Konda et al. 2014, Shi et al. 2013), one main disadvantage with the WW route is the large amount of water that is required in the water-wash step. For instance, depending on the biomass loading during pretreatment and process integration techniques employed (e.g., water recycling), water loading in water-wash step (i.e., the mass ratio between water required and dry biomass) could be as high as 50-150. These water requirements are not feasible in the context of an industrial scale integrated biorefinery. In addition to environmental concerns associated with the large water footprint, significant water usage has negative impact on capital and operating expenses in multiple sections in the plant (including pretreatment, wastewater treatment and cogeneration sections). Our preliminary TEA has shown that the novel pretreatment configurations, such as those that involve consolidation of pretreatment and saccharification, that address these cost-bottlenecks could potentially reduce minimum ethanol selling price (MESP) to $3/gal or less. Though the focus in this study is on the use of ILs, some of the findings from our study are generally applicable to any pretreatment process that uses solvents that are not compatible with commercial enzyme cocktails and fermentation hosts.

References:

• Konda NM, Shi J, Singh S, Blanch HW, Simmons BA, Klein-Marcuschamer D. 2014. Understanding cost drivers and economic potential of two variants of ionic liquid pretreatment for cellulosic biofuel production. Biotechnology for Biofuels 7: 86.
• Shi J, Gladden JM, Sathitsuksanoh N, Kambam P, Sandoval L, Mitra D, Zhang S, George A, Singer SW, Simmons BA. 2013. One-pot ionic liquid pretreatment and saccharification of switchgrass. Green Chem. 15: 2579-2589.