Techno-economic analysis of water precipitation for lignin value prior to pulping

Abstract Lignocellulosic biorefinery strategies are evolving to include recovering value from lignin as well as the sugar components. Dissolving the lignin in a solvent to separate it from the cellulose fraction is a popular strategy. Lignin solvation techniques must be paired with complementary lignin and solvent recovery strategies. Water precipitation to decrease the solvent concentration is a popular method of laboratory-scale lignin precipitation, but it requires solvent concentrations of 3–10% v/v. High lignin precipitation yields must be tempered by the economic challenges of recovering the dilute solvent in an industrial process. Herein we describe several solvent recovery strategies and their implementation for lignin value prior to pulping (LVPP) with water precipitation. We model the use of distillation, multi-effect evaporation, and reverse osmosis (RO) to concentrate and recover solvent. Two different solvents, low and high boiling, above and below water, (b.p. 120 °C), are concentrated from dilute to pretreatment solutions of 70% v/v and 90% v/v. We show that the annual costs of solvent recovery after water precipitation, given current industrial separation techniques, would be prohibitive for lignin commercialization due to a required lignin selling price of a few times its fuel value.