Techno‐economic analysis of cellulose dissolving ionic liquid pretreatment of lignocellulosic biomass for fermentable sugars production

Abstract Pretreatment of biomass is essential to produce fermentable sugars, which can be further transformed into biofuels. Most of the common pretreatment methods, including sulfuric acid pretreatment, lead to low sugar yields and high microbial inhibitors formation, and require an additional detoxification step prior to fermentation. Ionic liquid ( IL ) pretreatment has the potential to reduce or eliminate these problems, and, thus, recently, has gained significant attention as an alternative pretreatment technology. However, before commercial deployment, IL pretreatment requires a thorough assessment of its techno‐economic feasibilities and bottlenecks. Thus, the main objective of this study was to assess the techno‐economic feasibility of a commercial‐scale IL pretreatment for a 113 million liter/year (30 million gal/year) cellulosic biorefinery and identify operational targets for process improvement. 1‐ethyl‐3‐methylimidazolium acetate IL was used for analyses, which is one of the mostly investigated ILs and is currently best at dissolving the lignocellulosic biomass. Corn stover, poplar, and switchgrass were used as the model feedstock. Input data were obtained from recent literatures on IL pretreatment of these feedstocks. Estimated sugar production costs ($/kg) from corn stover, switchgrass and poplar were 2.7, 3.2, and 3.0, respectively. IL recovery was identified to be the most sensitive parameter followed by IL cost and heat recovery. Furthermore, for IL pretreatment to be economically competitive with sulfuric acid pretreatment, >97% IL recovery, ≤$1/kg IL cost, and >90% waste heat recovery are necessary, all of which are very optimistic considerations at the present state of technology, thus requires further research and development efforts. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd