Biomass Pre-Extraction as a Versatile Strategy to Improve Biorefinery Feedstock Flexibility, Sugar Yields, and Lignin Purity

Abstract

Feedstock flexibility is highly advantageous for the viability of (solvent-based) biorefineries but comes with the considerable challenge of having to cope with the varying nature and typically high abundance of nonlignocellulose compounds in the most readily available residual biomass streams. Here, we demonstrate that mild aqueous acetone organosolv fractionation of various complex lignocellulosic raw materials (roadside grass, wheat straw, birch branches, almond shells, and a mixed stream thereof) is indeed negatively affected by these compounds and present a versatile strategy to mitigate this bottleneck in biorefining. A biomass pre-extraction approach has been developed to remove the detrimental extractives with (aqueous) acetone prior to fractionation. Pre-extraction removed organic extractives as well as minerals, primarily reducing acid dose requirements for fractionation and loss of hemicellulose sugars by degradation and improved the purity of the isolated lignin. We show how pre-extraction affects the effectiveness of the biorefinery process, including detailed mass balances for pretreatment, downstream processing, and product characteristics, and how it affects solvent and energy use with a first conceptual process design. The integrated biorefining approach allows for the improved compatibility of biorefineries with sustainable feedstock supply chains, enhanced biomass valorization (i.e., isolation of bioactive compounds from the extract), and more effective biomass processing with limited variation in product quality.

Tuning the Properties of Biobased PU Coatings via Selective Lignin Fractionation and Partial Depolymerization

“…As described in a previous work, lignin aggregates, likely formed during lignin precipitation, do not fully dissociate in the 0.5 M NaOH solution used for SEC analysis leading to an overestimation of the lignin molar mass. 33 To resolve such an aggregation issue, the lignin was heated in methanol under an argon atmosphere (30 bar) to 150 °C, followed by immediate cooling and subsequent evaporation of the solvent to obtain a dry lignin sample that was subjected to SEC analysis. This procedure reduces aggregation, as reflected in the lower recorded lignin molar masses, without altering its structure or linkage abundance.…”

“…Acetone organosolv fractionation, the so-called Fabiola process, enables the isolation of sugars and lignin in relatively high yield and purity from a wide variety of lignocellulosic biomass streams. 29,30 The relatively mild pretreatment process preserves part of the cleavable ether bonds and thus produces a lignin that is less-condensed as compared to other technical lignins. The organosolv process was validated at pilot scale using industrial size beech wood chips, low liquid-to-solid ratios, and continuous lignin precipitation from the pulping liquor.…”

“…Beech wood lignin fractions, with molar masses ranging from roughly 1000 to 6000 g/mol, were obtained by stepwise precipitation of beech wood lignin from 60% aqueous acetone, gradually increasing the amount of water as antisolvent, similar to the earlier reports by Sadeghifar et al and Jaäskelaïnen et al 21,32 The as-is beech wood lignin and selected fractions are used as polyol for the formation of PU coatings. Additionally, the recently reported strategy for lignin partial depolymerization by reduction (PDR), 33 which aims to reduce lignin molar mass and dispersity by cleaving the remaining lignin β-aryl ethers using reductive conditions, was applied to the organosolv beech wood lignin and one of its high-molar-mass lignin fractions. PDR was successfully upscaled to the kilogram lignin scale to produce depolymerized lignin in sufficient quantity for application testing.…”

Laboratory- to Pilot-Scale Fractionation of Lignocellulosic Biomass Using an Acetone Organosolv Process

“…10 Compositional analyses of the pilot-scale feedstock and samples were performed by Celignis Analytical as described in the work of Pisano et al 20 Lignin characterization methods (SEC, 31 P NMR, and 2D HSQC-NMR) were conducted as described in the Supporting Information and in previous work. 21 The water-insoluble lignin (WIL) content in the pulping liquors was determined gravimetrically. The pulping liquor was first dried (60 °C/10 mbarA) until the weight was constant.…”

“…Biochemical composition analysis of feedstocks and pulps (L-BEC and L-BIC) as well as quantification of sugars and derivatives were conducted as described in previous work . Compositional analyses of the pilot-scale feedstock and samples were performed by Celignis Analytical as described in the work of Pisano et al Lignin characterization methods (SEC, 31 P NMR, and 2D HSQC-NMR) were conducted as described in the Supporting Information and in previous work . The water-insoluble lignin (WIL) content in the pulping liquors was determined gravimetrically.…”