Comparison between two different approaches for the deconstruction of lignocellulosic feedstocks using alkanolamine-based solvents

Abstract

Exploring the feasibility of applying alkanolamines as biomass pretreatment solvents for the deconstruction of biofuels is useful, owing to their ease of accessibility and their potential to serve as a low energy-intense, cost-effective downstream conversion. For the current study, we have selected a wide range of biomass feedstocks and evaluated biomass deconstruction efficiency using dual-functional solvents, ethanolamine and ethanolammonium acetate, and comparing two different solvent recovery approaches – water washing and solvent evaporation. Pretreatment conditions for both processes included 15% solid loading of 2 mm size ground and homogeneously mixed biomass with pure ethanolamine (EA) and ethanolammonium acetate (EAA) at 140 °C for 3 h. For the first solvent removal process, the pretreated biomass was washed until the pH reached 7.0, and for the second solvent removal process, solvent evaporation was performed in a vacuum oven set at 80 °C and 140 °C for EA and EAA respectively, followed by pH adjustment to 5.0. The next step involved saccharification using Cellic® enzymes to liberate glucose and xylose from the pretreated solids. Enzymatic hydrolysis of coconut chips, hay, rice hulls and a pelletized 4-crop blended mix (corn stover, switchgrass, pine, and eucalyptus) revealed significantly higher sugar release through the solvent evaporation route as compared to the washing process as washing led to high solid losses. Through this study, we demonstrated the effective use of alkanolamines as biomass pretreatment solvents relevant to a commercial biorefinery setting, as well as that vacuum-based solvent removal is a better strategy for improved release of fermentable sugars that also enables facile solvent removal.