With the aim of understanding the contribution of enzymes to the cost of lignocellulosic biofuels, we constructed a techno-economic model for the production of fungal cellulases. We found that the cost of producing enzymes was much higher than that commonly assumed in the literature. For example, the cost contribution of enzymes to ethanol produced by the conversion of corn stover was found to be $0.68/gal if the sugars in the biomass could be converted at maximum theoretical yields, and $1.47/gal if the yields were based on saccharification and fermentation yields that have been previously reported in the scientific literature. We performed a sensitivity analysis to study the effect of feedstock prices and fermentation times on the cost contribution of enzymes to ethanol price. We conclude that a significant effort is still required to lower the contribution of enzymes to biofuel production costs.

The cost of ionic liquids (IL) is one of the main impediments to IL utilization in the cellulosic biorefinery, especially in the pretreatment step. In this study, a number of ionic liquids were synthesized with the goal of optimizing solvent cost and stability whilst demonstrating promising processing potential. To achieve this, inexpensive feedstocks such as sulfuric acid and simple amines were combined into a range of protic ionic liquids containing the hydrogen sulfate [HSO 4 ] -anion. The performance of these ionic liquids was compared to a benchmark system containing the IL 1-ethyl-3-methylimidazolium acetate [C 2 C 1 im][OAc]. The highest saccharification yields were observed for the triethylammonium hydrogen sulfate IL, which was 75% as effective as the benchmark system. Techno-economic modeling revealed that this promising and yet to be optimized yield was achieved at a fraction of the processing cost. This study demonstrates that some ILs can compete with the cheapest pretreatment chemicals, such as ammonia, in terms of effectiveness and process cost, removing IL cost as a barrier to the economic viability of IL-based biorefineries.

Lignocellulose dissolution in ionic liquids is a relatively new biomass pre-treatment technology that is receiving growing interest from the biofuels community as a route to provide readily-hydrolyzable holocellulose.Despite its proven advantages over other pre-treatment technologies -including feedstock invariance, high monomeric sugar yields over short saccharifi cation times, and extensive delignifi cation -there are several core issues that stand in the way of commercialization. These include the relative high cost of the ionic liquids themselves, a lack of knowledge in terms of process considerations for a biorefi nery based on these solvents, and scant information on the coproducts this pre-treatment technology could provide to the marketplace. We present an initial techno-economic model of a biorefi nery that is based on the ionic liquid pre-treatment technology and have identifi ed, through a comprehensive sensitivity analysis, the most signifi cant areas in terms of cost savings/revenue generation that must be addressed before ionic liquid pre-treatment can compete with other, more established, pre-treatment technologies. This report evaluates this new pre-treatment technology through the perspective of a virtual operating biorefi nery, and although there are signifi cant challenges that must be addressed, there is a clear path that can enable commercialization of this novel approach.