Tree bark is normally a side-stream product but by an integrated bark biorefinery approach, valuable compounds may be recovered and used to replace fossil-based products. Norway spruce bark was extracted to obtain cellulose, which was chemically treated to produce cellulose oxalate (COX) which was homogenized to yield nanocellulose. The nanocellulose was used to produce Pickering emulsions with almond oil and hexadecane as organic phases. COX from dissolving pulp was used to study the effect of various raw materials on the emulsifying properties. The COX samples of bark and dissolving pulp contained a significant amount of hemicelluloses, which affected the viscosity results. The emulsion properties were affected by the organic phases and the aspect ratio. Emulsions using hexadecane were more stable than the emulsions using almond oil. Since the aspect ratio of bark was lower than that of the dissolving pulp, the emulsifying properties of the COX dissolving pulp was better. It has been shown that nanocellulose from cellulose oxalate of both spruce bark and dissolving pulp is a promising substitute for petroleum-based emulsifiers and surfactants. By utilizing bark, value-added products can be produced which may be economically beneficial for various industries in the future and their aim for climate-neutral products.

The interest in the bark and the attempt to add value to its utilization have increased over the last decade. By applying an integrated bark biorefinery approach, it is possible to investigate the recovery of compounds that can be used to develop green and sustainable alternatives to fossil-based materials. In this work, the focus is on extracting Norway spruce (Picea abies) bark lignin via organosolv extraction. Following the removal of the extractives and the subcritical water extraction to remove the polysaccharides, a novel cyclic organosolv extraction procedure was applied, which enabled the recovery of lignin with high quality and preserved structure. Main indicators for low degradation and preservation of the lignin structure were a high β-O-4' content and low amounts of condensed structures. Furthermore, high purity and low polydispersity of the lignin were observed. Thus, the obtained lignin exhibits high potential for use in the direct development of polymer precursors and other bio-based materials. During the extraction sequence, around 70% of the bark was extracted. Besides the lignin, the extractives as well as pectic polysaccharides and hemicelluloses were recovered with only minor degradation, which could potentially be used for the production of biofuel or other high-value products such as emulsifiers or adhesives.

It is shown that the isolation of nanocellulose in a biorefinery approach adds value to the bark and its components. The utilization of a chlorine-free delignification and the preparation of cellulose oxalate in a solvent-free process are an economic and environmentally advantageous way of applying the biorefinery concept and to use the bark in a sustainable way. The properties of cellulose oxalate from delignified bark were determined, and the morphological structure of the isolated nanocellulose was characterized. The chemical composition and thermal properties were monitored during the extraction and separation steps, and it was possible to prepare cellulose oxalate in a yield of 82% with a degree of substitution of 0.3 and surface charge of 1.53 mmol g(-1). The isolated nanocellulose was found to be a mixture of rodlike nanocrystals and nanofibrils. Initial thermal analysis of the isolated nanocellulose shows promising properties. The results show that the bark is a potential inexpensive source of high-value nanocellulose that can be isolated in high yield, for use in cosmetics or as reinforcement in nanocomposites. Since the isolated nanocellulose contains two different morphological types, it can be used where the properties of both cellulose nanocrystals and cellulose nanofibrils are required.

The ‘circular economy’ concept envisages deriving the maximum value out of resources and reducing waste to a minimum. In textiles, that includes the recovery of fiber materials out of used clothing and reusing them in the construction of new clothes. Processes such as mechanical separation, depolymerization treatment, and selective dissolutions of individual polymers are applied. We investigate the approach of selective nondestructive dissolution and recovery of polyamide fiber from mixed textile waste by using the solvent system CaCl2/ethanol/water (CEW) based on complexation and decomplexation of polyamide (PA). The results show that PA is precipitated and decomplexed by simple addition of water and a substantial amount of previously incorporated calcium by complexation, is removed. The recovered polyamide shows properties similar to pristine polyamide. Investigation on a mixed textile waste model of polyamide/wool demonstrates that CEW treatment can successfully separate different fiber materials. The nondestructive approach in dissolving PA using CEW, clearly shows the benefit, that PA fiber can be separated by controlled complexation/decomplexation without degradation, thus avoiding the repolymerization step. Furthermore, the solvent system is made of abundantly available materials that are inexpensive and used widely in industrial-scale operations. Thus, the concept will make significant contribution to a green textile recycling approach. 

The bark of Norway spruce (Picea abies) contains up to 13% pectins that can be extracted by pressurized hot water, which constitute a valuable renewable resource in second-generation lignocellulosic biorefineries. This article proposes, for the first time, structural molecular models for the pectins present in spruce bark. Pectin fractions of tailored molar masses were obtained by fractionation of the pressurized hot water extract of the inner bark using preparative size-exclusion chromatography. The monosaccharide composition, average molar mass distribution, and the glycosidic linkage patterns were analyzed for each fraction. The pectin fraction with high molecular weight (M-w of 59,000 Da) contained a highly branched RG-I domain, which accounted for 80% of the fraction and was mainly substituted with arabinan and arabinogalactan (type I and II) side chains. On the other hand, the fractions with lower molar masses (M-w = 15,000 and 9000 Da) were enriched with linear homogalacturonan domains, and also branched arabinan populations. The integration of the analytical information from the macromolecular size distributions, domain composition, and branch lengths of each pectin fraction, results in a comprehensive understanding of the macromolecular architecture of the pectins extracted from the bark of Norway spruce. This paves the way for the valorization of spruce bark pectic polymers in targeted applications based on their distinct polymeric structures and properties.

Many biopolymers exhibit a strong complexing ability for multivalent ions. Often such ions form ionic bridges between the polymer chains. This leads to the formation of ionic cross linked networks and supermolecular structures, thus promoting the modification of the behavior of solid and gel polymer networks. Sorption of biopolymers on fiber surfaces and interfaces increases substantially in the case of multivalent ions, e.g., calcium being available for ionic crosslinking. Through controlled adsorption and ionic crosslinking surface modification of textile fibers with biopolymers can be achieved, thus altering the characteristics at the interface between fiber and surrounding matrices. A brief introduction on the differences deriving from the biopolymers, as their interaction with other compounds, is given. Functional models are presented and specified by several examples from previous and recent studies. The relevance of ionic crosslinks in biopolymers is discussed by means of selected examples of wider use.