Organosolv Fractionation of Birch Sawdust: Establishing a Lignin-First Biorefinery

Abstract

The use of residual biomass for bioconversions makes it possible to decrease the output of fossil-based chemicals and pursue a greener economy. While the use of lignocellulosic material as sustainable feedstock has been tried at pilot scale, industrial production is not yet economically feasible, requiring further technology and feedstock optimization. The aim of this study was to examine the feasibility of replacing woodchips with residual sawdust in biorefinery applications. Woodchips can be used in value-added processes such as paper pulp production, whereas sawdust is currently used mainly for combustion. The main advantages of sawdust are its large supply and a particle size sufficiently small for the pretreatment process. Whereas, the main challenge is the higher complexity of the lignocellulosic biomass, as it can contain small amounts of bark and cambium. Here, we studied the fractionation of birch sawdust by organosolv pretreatment at two different temperatures and for two different durations. We evaluated the efficiency of fractionation into the three main fractions: lignin, cellulose, and hemicellulose. The cellulose content in pretreated biomass was as high as 69.2%, which was nearly double the amount in untreated biomass. The obtained lignin was of high purity, with a maximum 4.5% of contaminating sugars. Subsequent evaluation of the susceptibility of pretreated solids to enzymatic saccharification revealed glucose yields ranging from 75% to 90% after 48 h but reaching 100.0% under the best conditions. In summary, birch sawdust can be successfully utilized as a feedstock for organosolv fractionation and replace woodchips to simplify and lower the costs of biorefinery processes.

Salicornia dolichostachya organosolv fractionation: towards establishing a halophyte biorefinery

“…In our previous study with birch ( Betula pendula L.) sawdust, the M w ranged from 1800 Da (180 °C for 15 min with 50% v/v ethanol) to 15 900 Da (180 °C for 30 min with 60% v/v ethanol). 35 When using birch chips, the M w ranged from 2700 Da (200 °C for 15 min with 60% ethanol and 1% w/w biomass H 2 SO 4 ) to 8000 Da (200 °C for 30 min with 60% ethanol without catalyst). 36 Pine wood pretreated at 190 °C for 60 min with 60% v/v ethanol and 1% w/w biomass H 2 SO 4 generated lignins with M w of 7700 Da; whereas cotton stalks pretreated at 200 °C for 45 min with 50% v/v ethanol and 1% w/w biomass H 2 SO 4 , as well as sweet sorghum bagasse pretreated at 180 °C for 30 min with 60% v/v ethanol produced lignins with M w of 16 800 Da and 6600 Da, respectively.…”

Valorization of sawdust biomass for biopolymer extraction via green method: Comparison with conventional process

“…Recent researchers on the SW topic in which the contribution related to C, L and H are highlighted are shown in Table S1. As noted, most studies focus on C, L and H contents in raw SW, but not after pretreatment, which is key for final properties 54,55,57‐61 . In fact, some works do not report data of the initial composition 56 .…”

“…In this sense, the most recent works focus on obtaining microfibrillated (MFC) 55 and nanocrystalline cellulose 56 from SW residues 54 . These reports include an analysis of the synthesis parameters and their influence on the degree of crystallinity degree, 54,56,59 morphologies, 55,60 conductivity and compressibility 57 as well as yield of hemicellulose 59 and lignin after pretreatment to obtain glucose 61 . Unfortunately, polymorphic content, which is key to determine potential applications, is missing from those works.…”

“…As noted, most studies focus on C, L and H contents in raw SW, but not after pretreatment, which is key for final properties. 54,55,[57][58][59][60][61] In fact, some works do not report data of the initial composition. 56 The only is the case of sulfonated SW 59 in which the products after the isolation of hemicellulose and cellulose during a multiproduct biorefinery process were analyzed.…”

“…54 These reports include an analysis of the synthesis parameters and their influence on the degree of crystallinity degree, 54,56,59 morphologies, 55,60 conductivity and compressibility 57 as well as yield of hemicellulose 59 and lignin after pretreatment to obtain glucose. 61 Unfortunately, polymorphic content, which is key to determine potential applications, is missing from those works. Thus, to our knowledge, overall valorization of side-streams is rarely included in previous reports 57,58 which does not allow to accurately predict the final properties of a product.…”