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

The costs of sugar production from different feedstocks and processing technologies

“…75 The ionic liquid pretreatment has higher fixed capital costs than other pretreatments because of the special storage requirements for ionic liquids. 76 The assumptions for miscanthus-derived sugar production are similar to those reported in Davis et al 69 Enzymes are produced in the plant, so the fixed capital costs increase by approximately 14%. 71 In the study by Boakye-Boaten et al, 71 the capital investment in hydrolysis, 40.83 million dollars, was also included in fermentation.…”

“…The lower fixed capital costs reported by Yang and Rosentrater might result from the Lang factor and estimations of other indirect capital investments . The ionic liquid pretreatment has higher fixed capital costs than other pretreatments because of the special storage requirements for ionic liquids …”

“…The sugar production cost with the LMAA (low‐moisture anhydrous ammonia) pretreatment was estimated to be $0.54/kg by Yang and Rosentrater . Baral and Shah reported a high sugar production cost using a ionic liquid based process ($2.84/kg) due to the high costs of the ionic liquid and anti‐solvent, despite recycling of the solvent …”

“…for miscanthus . The highest production cost, which is approximately $3.37/kg, is associated with the ionic liquid pretreatment …”

Synergistic effect of pretreatment with dimethyl sulfoxide and an ionic liquid on enzymatic digestibility of white poplar and pine

“…14,18,19 Great progress has been made on understanding the relationship between IL pretreatment, structural features of lignocelluloses and hydrolytic efficiency. 14,18,24 However, EmimAc is expensive 25 and highly viscous. 8,[20][21][22][23] Among the various ILs that have been tested for biomass pretreatment, 1-ethyl-3methylimidazolium acetate (EmimAc) is one of the mostly investigated ILs and has been shown to be able to handle a variety of biomasses.…”