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The overall target of this project, called Bioforest, is to develop an economic process for the production of commodity chemicals from mixed forest biomass, consisting of logging residues of hardwoods (HW) and softwoods (SW) and also from recycled fibers. The aim is to dissolve the biomass lignin and to produce monosugars based on hemicelluloses and hydrolyzed cellulose in high yield. The hydrolyzate could subsequently be converted into chemicals by modified acetone-butanol-ethanol fermentation. Here, the total mass balances of SO2-ethanol-water fractionation of different types of biomass feedstocks, such as SW and HW biomass, and deinked pulp are presented. Chemical composition of the feedstocks, solid residues (pulps) and spent liquors of fractionation were analyzed to gain more understanding about the fractionation procedure. The analysis was focused on carbohydrates, lignin, ash, acetyl groups and sugar degradation products. It was also examined if all feedstocks could be treated simultaneously in one digester because a larger feedstock supply within an economic transport radius improves the viability of the process. The fractionation approach was successful and it can be concluded that the method presented is very versatile for future applications in lignocellulosic biorefineries. [ABSTRACT FROM AUTHOR]

In a forest based biorefinery, pulp and paper are the main products, while side-streams are utilized for value-added products. One biorefinery concept is to remove hemicelluloses from wood by extraction prior to pulping and converting them into biofuels or chemicals. This study presents a concept of a larch wood based biorefinery and focuses on the mass balance of pre-extraction. Sugar rich extracts were obtained by hot water extraction of Siberian larch ( Larix sibirica Lebed.) wood chips at different temperatures and times. At 160°C and 60-90 min the extract contains 13-16% hemicelluloses (on wood). The composition of extracts and extracted wood has been determined to have a basis for mass balances. Fermentation of the hydrolyzed extract with Bacillus coagulans MXL-9 resulted in consumption of all C6 and C5 sugars and produced lactic acid in high yield. In an earlier work, it was demonstrated that water pre-extraction of larch chips followed by polysulfide-anthraquinone (PSAQ) pulping still produced a good papermaking pulp at a yield comparable to the corresponding non-extracted kraft pulp. Accordingly, the present results show that a larch wood based biorefinery has a potential for industrial application. [ABSTRACT FROM AUTHOR]

Bacillus coagulans MXL-9 was found capable of growing on pre-pulping hemicellulose extracts, utilizing all of the principle monosugars found in woody biomass. This organism is a moderate thermophile isolated from compost for its pentose-utilizing capabilities. It was found to have high tolerance for inhibitors such as acetic acid and sodium, which are present in pre-pulping hemicellulose extracts. Fermentation of 20 g/l xylose in the presence of 30 g/l acetic acid required a longer lag phase but overall lactic acid yield was not diminished. Similarly, fermentation of xylose in the presence of 20 g/l sodium increased the lag time but did not affect overall product yield, though 30 g/l sodium proved completely inhibitory. Fermentation of hot water-extracted Siberian larch containing 45 g/l total monosaccharides, mainly galactose and arabinose, produced 33 g/l lactic acid in 60 h and completely consumed all sugars. Small amounts of co-products were formed, including acetic acid, formic acid, and ethanol. Hemicellulose extract formed during autohydrolysis of mixed hardwoods contained mainly xylose and was converted into lactic acid with a 94% yield. Green liquor-extracted hardwood hemicellulose containing 10 g/l acetic acid and 6 g/l sodium was also completely converted into lactic acid at a 72% yield. The Bacillus coagulans MXL-9 strain was found to be well suited to production of lactic acid from lignocellulosic biomass due to its compatibility with conditions favorable to industrial enzymes and its ability to withstand inhibitors while rapidly consuming all pentose and hexose sugars of interest at high product yields. [ABSTRACT FROM AUTHOR]

The enzymatic hydrolysis of hardwood and softwood harvest residues treated by SO2-ethanol-water (SEW) fractionation was studied. The target was to convert these fibers with high yield into glucose monomers which could be further converted into biofuel by a subsequent fermentation stage. Hardwood biomass residues were efficiently digested at low enzyme dosage (5 FPU/g cellulose) whereas the softwood residues required notably higher enzyme dosage (20 FPU) for sufficient conversion. However, cellulase dosage of softwood could be reduced mannanase supplementation. Especially the high lignin content of softwood biomass pulps impairs the digestibility and thereby, improved delignification could notably enhance the hydrolysis yields. It was shown that inferior delignification of SW biomass is due to persistent polyphenolic acids present in coniferous bark, whereas no evidence of the negative effect of inorganics and acetone extractives was observed. Additionally, SW hydrolyzate was successfully converted into a mixture of butanol, acetone and ethanol through ABE fermentation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Oil palm empty fruit bunches (OPEFB) are fractionated by SO2–ethanol–water mixture. [•] Fractionation of OPEFB feedstock produces cellulosic fibers and spent liquor. [•] Spent liquor contains dissolved hemicellulose sugars (mostly monomers) and lignin. [•] Fractionation and sugar hydrolysis is hindered by the high cation content of OPEFB. [•] Acidic leaching of OPEFB only partly removes cations; more intense deashing needed. [Copyright &y& Elsevier]

Abstract: SO2–ethanol–water (SEW) spent liquor from spruce chips was successfully used for batch and continuous production of acetone, butanol and ethanol (ABE). Initially, batch experiments were performed using spent liquor to check the suitability for production of ABE. Maximum concentration of total ABE was found to be 8.79g/l using 4-fold diluted SEW liquor supplemented with 35g/l of glucose. The effect of dilution rate on solvent production, productivity and yield was studied in column reactor consisting of immobilized Clostridium acetobutylicum DSM 792 on wood pulp. Total solvent concentration of 12g/l was obtained at a dilution rate of 0.21h−1. The maximum solvent productivity (4.86g/lh) with yield of 0.27g/g was obtained at dilution rate of 0.64h−1. Further, to increase the solvent yield, the unutilized sugars were subjected to batch fermentation. [Copyright &y& Elsevier]

The objective of this study is to develop a process for conditioning spent liquor produced by SO2-ethanol-water (SEW) fractionation of spruce wood chips for fermentation to butanol, ethanol and acetone/isopropanol, i.e., by means of the so called acetone-butanol-ethanol (ABE) process using Clostridia bacteria. This study serves as part of an overall project aiming at the development of economic processes for producing chemicals and biofuels from mixed forest biomass via SEW fractionation and ABE fermentation technologies. [ABSTRACT FROM AUTHOR]