A techno-economic assessment of an upgrading procedure and outtake of a pre-hydrolysate in a presumed dissolving pulp mill was performed. Pre-hydrolysis of spruce wood chips in pilot scale produced input data for energy and mass balances and was performed with and without subsequent membrane filtration to produce hydrolysate fractions rich in galactoglucomannan and with some lignin. The hydrolysate is a viable raw material for the production of renewable thin oxygen barrier films as demonstrated herein in the formulation of free standing films with very low oxygen permeability at both moderate and high relative humidities. Approximately 50,000 ton dry solid upgraded pre-hydrolysate suitable for production of oxygen barriers could be produced according to the presumed dissolving pulp mill producing about 500,000 air dry ton dissolving pulp per year and applying a liquor to wood ratio of 4:1. Utilization of the pre-hydrolysis liquor hence adds value to and realizes the dissolving plant as a biorefinery. A sensitivity analysis indicates that the market price of the upgraded pre-hydrolysate has the largest positive effect on the return on investment for separation and upgrading of a pre-hydrolysate. Increased investment cost and increased annuity factor show negative effects.

Birch chips were subjected to pilot-scale pre-hydrolysis under various sets of conditions to mimic a pre-hydrolysis step in a dissolving pulp process. The process generates residual process liquor, a wood hydrolysate, and the treated chips may be directly utilized in a dissolving process. The wood hydrolysates were rich in xylan and utilized in the production of fully renewable films that provide very good oxygen barrier function and mechanical integrity also at high relative humidity. Membrane filtration had an effect in enriching higher molecular weight fractions from the hydrolysates, but noteworthy, a hydrolysate used in the crude state without any membrane filtration performed just as well as upgraded fractions in forming films providing acceptable tensile properties and a good barrier against oxygen permeation.

Two types of hemicellulose-based spruce wood hydrolysates were upgraded through ultrafiltration and diafiltration to separate the higher molecular weight fraction of the wood hydrolysates. Upgraded wood hydrolysates were thereafter used, together with different co-components to produce films with very good oxygen barrier properties and acceptable mechanical properties.

A scaled-up prehydrolysis process was elaborated to demonstrate an industrially feasible operation step in a pulping process that generates a valuable side product in addition to the cellulose pulp. The valuable side product is aqueous process liquor, a softwood hydrolysate (SWH) herein produced in 60 L batches, and its components were recovered and utilized as materials. The process parameters were shown to influence the yield, composition, and quality of the obtained hydrolysates. Furthermore, the process conditions were shown to influence the ability of SWHs to form free-standing, foldable films in blends with either microfibrillated cellulose (MFC) or carboxymethyl cellulose (CMC). Films with oxygen permeabilities (OP) as low as 0.35 cm 3 ÎŒm day -1 m -2 kPa -1 at 50% relative humidity, were produced from aqueous solutions providing a viable and green alternative to petroleum-based packaging barriers. The OPs were very low regardless of SWH film composition and upgrading conditions, whereas the films' tensile performance was directly controlled by the ratio of SWH to cocomponent.

A wood hydrolysate derived hemicellulose-rich fraction was functionalized with L-lactide oligomers through a ring opening polymerization mediated grafting-from reaction. The graft copolymer was designed to act as a compatibilizer in hydrolysate/poly(L-lactide) (PLLA) blend films. The PLLA addition improved the tensile behavior of the hydrolysate matrix and this effect was enhanced further by the addition of minor amounts of the synthesized compatibilizer. With only 1% (w/w) of compatibilitzer the compatibility between the components and the homogeneity of the resulting films were greatly improved with an increase of strain-at-break with up to 400%. The oxygen permeability of the blend films was markedly reduced with the addition of wood hydrolysate, compared to the barrier properties of pure PLLA, an effect that is not significantly compromised when compatibilizer amounts are kept small.