Alkanolamines as Dual Functional Solvents for Biomass Deconstruction and Bioenergy Production

Abstract

This work demonstrates the feasibility of applying dual functional solvents called alkanolamines towards the conversion of biomass into biofuels. Alkanolamines have the potential to serve as effective pretreatment solvents that promote a low energy intensity, process intensification, and downstream conversion via a cost-effective route. Several key factors were considered to effectively integrate the pretreatment technology into a biorefinery, including solvent screening (both experimentally and computationally), feedstock screening (capturing the effectiveness on softwood, hardwood, and grasses), fractionation of lignocellulose components (lignin removal), bioconversion efficacy, and a sustainability impact assessment. After a thorough and systematic optimization, the following conditions emerged for optimal process economics (i.e., shortest time, lowest temperature, and highest solid loading): pretreatment of sorghum biomass via ethanolamine (25% solvent in water) with temperature 100 °C, time 1 h and solid loading 40%. These conditions generated yields of 90% glucose, 76% xylose, 59% lignin removal, and 73% solid recovery. The pretreated biomass and recovered lignin were studied using PXRD/TGA/FTIR/NMR analyses, revealing that the morphology and crystallinity of biomass does not change after pretreatment, and recovered lignin is dominated by guaiacyl groups, which are suitable for lignin valorization. Subsequently the process was consolidated and scaled up (40X) to generate >99% sugar yields followed by a test of bioconversion using the omnivorous host R. toruloides, which converted >97% C5, C6 and phenolic into the biofuel precursor bisabolene at a titer of 1155 mg L⁻¹. The TEA revealed that the cost of biomass deconstruction was severely reduced (up to 50%) compared to similar pretreatment methods, including ethanolamine acetate and cholinium lysinate, evaluated under the same modeling assumptions. This study has demonstrated the effectiveness and robustness of alkanolamines towards biomass processing and presents a new solvent group to be considered for biomass pretreatment within a commercial biorefinery for the deconstruction of lignocellulosic biomass.