Future biorefineries must upgrade all constituents of lignocellulosic feedstocks to high-value products. To curb land-use pressure, technologies that upgrade existing side-streams from forestry and agriculture into substitutes for high-impact, fossil-derived materials are urgently needed. Prevailing biomass valorization typically prioritizes either cellulose pulp or lignin; true co-valorization remains uncommon. Here we report a metal-free, ambient-pressure reactive fractionation that concurrently yields high-quality cellulose and a functionalized lignin. The isolated lignin is etherified and subsequently covalently coupled to cellulose via epoxide ring-opening, producing a composite. The materials display mechanical performance equivalent to common packaging materials, with retention under wet conditions, overcoming the intrinsic limitations of hydrogen-bonded cellulose networks. By integrating mild fractionation with chemical upgrading, this strategy simplifies processing, broadens the product slate accessible from residual biomass side streams and advances the substitution of problematic packaging materials. These findings establish a scalable route to whole-biomass co-valorization and wet-tolerant bio-based packaging from residual streams.

In this study, cellulose-based films were developed by using microfibrillated cellulose (MFC) and lignin-containing microfibrillated cellulose (Lig-MFC) derived from sequentially extracted spruce bark. The films were coated with the hydrophilic extractives from the fractionation, resulting in additional MFC-coated and Lig-MFC-coated cellulose films. A combination of morphological (AFM), surface (water contact angle (WCA), roughness), optical (UV–vis), and mechanical properties was analyzed to assess structure–property relationships. Coated films exhibited significantly enhanced hydrophobicity and UV-shielding, with WCA increasing from 47° to 76° for MFC and from 66° to 71° for Lig-MFC. Notably, MFC-coated films displayed superior mechanical performance, with a tensile strength of 119 MPa and elongation of 11%, surpassing most lignocellulosic-based films in the literature derived from bark. In addition, this tensile strength falls within or above the range of commonly used materials, such as kraft liner, PET, and LDPE, suggesting realistic opportunities for substitution in short-lived packaging applications. AFM analysis revealed a reduction in surface roughness after coating, correlating with an enhanced WCA. Compared with similar biobased films in the literature, the extractive-coated MFC films show superior performance in terms of strength, flexibility, and UV-shielding properties. This valorization route offers both economic and environmental sustainability advantages compared with incineration for energy recovery. A comparative life cycle assessment (LCA) study showed that valorization of the pulp and hydrophilic extractives from the bark biorefinery into different qualities of MFCs gave substantial climate change benefits stemming from the possibility of substituting packaging materials with high inherent environmental impact.

Bark represents 10 % dry weight of spruce trees and is a major side stream from pulp production. Currently, pulp mills burn bark to produce energy with a low economic value, directly emitting biogenic carbon dioxide to the atmosphere. Biorefining bark using a continuous flow-through fractionation process generates high added-value compounds (tall oil, starch, phenol, and pulp) that allow for extended carbon storage durations. This study assesses the potential future environmental impacts of valorising bark instead of burning it. We conduct a LCA study combining a prospective consequential modelling perspective with an input-related functional unit and account for the effects of storing biogenic carbon in the bark-based products. Our findings show that biorefining bark maintains lower environmental impacts than combustion, reducing time-differentiated climate impacts by up to 30 %, but only when the carbon dioxide used for pulping is recirculated and the fractionation processes are integrated with a co-located pulp mill supplying surplus waste energy, considered to have no associated environmental impacts. Storing biogenic carbon for a longer period of time has a positive effect on mitigating short-term climate impacts. However, our analysis reveals that while time-dependent climate impacts decrease, there is an increase in human toxicity and ecotoxicity impacts, with combustion performing better in these categories. This highlights the importance of expanding the scope of LCA studies to include impacts beyond climate change. Overall, this work demonstrates that combining a prospective consequential modelling perspective with an input-related functional unit is a relevant approach to study potential future impacts of emerging biorefineries and thus supports the development of a sustainable circular bioeconomy.

This thesis explores strategies for upgrading underutilized streams, focusing on hemp hurd, softwood bark lignin, and plastics. Catalysis plays a crucial role in overcoming challenges in upgrading and efficiently converting residual streams into valuable products. By exploring lignocellulosic biomass fractionation, this research tackles the complexities of converting biomass side streams into sustainable, marketable products. Additionally, it investigates methods for recycling polyesters, particularly PET, to integrate plastic waste into a circular economy.

 The valorization of different biomass feedstocks, such as hemp hurd and softwood bark, requires tailored catalytic processes due to their distinct compositions. For example, reductive catalytic fractionation (RCF) is highly effective for hemp hurd, rich in syringyl lignin, yielding monophenolic compounds and dissolving-grade pulp for textiles and nanocellulose production. Oxidative catalytic fractionation (OCF) works better for softwood bark, as it cleaves not only the predominant β–O–4 linkages but also additional lignin bonds, enhancing the yield of monophenolic products such as vanillin. This highlights the importance of selecting the appropriate catalytic methods based on feedstock characteristics.

 However, both OCF and RCF traditionally rely on expensive noble metal catalysts. As an alternative, an organocatalytic approach is introduced through a lignin condensation strategy that preserves cleavable β-ether units to produce high-performance bisphenols. Organocatalysis is also applied to the recycling of PET, enabling the recovery of valuable monomers and facilitating the recycling of polycotton waste into high-quality viscose fibers and chemicals.

 This thesis presents approaches to upgrading residual streams, demonstrating how catalysis-based strategies can be used in transforming low-value byproducts into valuable chemicals and materials.

Condensation of glycerol with bioderived carbonyls yields cyclic ketals with unique properties. In this study, efficient solvent-free heterogeneously catalyzed ketalization has been achieved to give the corresponding products in good to excellent yields. Substrate-to-glycerol ratios of 1:1 have been used; the reactions were performed at 120 °C for 30 min. By using an acid-treated H-ZSM-5 catalyst, high selectivity to a five-membered ring was achieved. Furthermore, the catalyst could be recycled up to 4 times without losing activity. The ketal from glycerol and levulinic acid (GLK) was isolated and applied as a solvent in oil color paint and showed advantageous properties over commercial paint solvents in terms of aging.

Polyethylene terephthalate (PET) is one of the most common plastics and can be cascaded mechanically during its life cycle. However, recycling affects the mechanical properties of the material, and the virgin material is constantly in demand. If a worn material could be depolymerized to its chemical building blocks, then a virgin polymer could be generated from old fibers. In this work, we have developed a benign organo-catalytic depolymerization of PET to yield dimethyl terephthalate (DMT) and ethylene glycol (EG) without the need for purification of generated monomers. By recirculating the solvent and organo-catalyst, a solvent/substrate ratio of 3:1 was achieved. The depolymerization was successfully applied to other polyesters, polycarbonates, and polycotton. The cotton isolated from the polycotton depolymerization was successfully processed into viscose fibers with a tenacity in the range of nonwaste cotton-derived viscose filaments. The global warming potential (GWP) of PET depolymerization was evaluated by using life cycle assessment (LCA). The GWP of 1 kg PET recycling is 2.206 kg CO₂ equivalent, but the process produces DMT, EG, and heat, thereby avoiding the emissions equivalent to 4.075 kg CO₂ equivalent from the DMT, EG, and steam-energy production through conventional pathways. Thus, the net result potentially avoids the emission of 1.88 kg of CO₂ equivalent. The impact of this process is lower than that of waste PET incineration and conventional PET recycling technologies.

Lignocellulose is mainly composed of hydrophobic lignin and hydrophilic polysaccharide polymers, contributing to an indispensable carbon resource for green biorefineries1,2. When chemically treated, lignin is compromised owing to detrimental intra- and intermolecular crosslinking that hampers downstream process3,4. The current valorization paradigms aim to avoid the formation of new C–C bonds, referred to as condensation, by blocking or stabilizing the vulnerable moieties of lignin5–7. Although there have been efforts to enhance biomass utilization through the incorporation of phenolic additives8,9, exploiting lignin’s proclivity towards condensation remains unproven for valorizing both lignin and carbohydrates to high-value products. Here we leverage the proclivity by directing the C–C bond formation in a catalytic arylation pathway using lignin-derived phenols with high nucleophilicity. The selectively condensed lignin, isolated in near-quantitative yields while preserving its prominent cleavable β-ether units, can be unlocked in a tandem catalytic process involving aryl migration and transfer hydrogenation. Lignin in wood is thereby converted to benign bisphenols (34–48 wt%) that represent performance-advantaged replacements for their fossil-based counterparts. Delignified pulp from cellulose and xylose from xylan are co-produced for textile fibres and renewable chemicals. This condensation-driven strategy represents a key advancement complementary to other promising monophenol-oriented approaches targeting valuable platform chemicals and materials, thereby contributing to holistic biomass valorization.

This study presents a sequential fractionation of spruce bark employing a flow-through system that enables continuous extraction without the need to change the chamber during the process. Various bark components such as lipophilic extractives, noncellulosic sugars, and lignin were extracted under mild conditions and within short timeframes compared to the batch process. The utilization of the flow-through system enabled efficient extraction without degradation of products that were observed during the batch process. By recirculating the solvents containing extracted components, the solvent/biomass ratio could be reduced considerably, without degradation of the products. The results demonstrate an energy efficient approach to obtaining valuable components from spruce bark, paving the way for a future biorefinery.

To make biorefining more environmentally sustainable, preferably residues from forestry should be used and more than one fraction should be upgraded. A third of raw materials from forestry & horbar;tops and branches (T & B)― are either left in the forests or collected and incinerated to a low value. Herein, we apply a fast fractionation to valorize two of the fractions of this forestry residue. The cellulose is converted to textile fibers and all the lignin to hydrocarbons. The environmental sustainability of the novel value chain was studied by life cycle assessment (LCA), and benefits were found in four out of five impact categories. These are important steps to increase fiber production without affecting environmental impact, making biorefining competitive.

Despite the increased use of hemp fiber, negligible attention has been given to upgrade the hemp hurd, which constitutes up to 70 wt % of the hemp stalk and is currently considered a low-value byproduct. In this work, valorization of hemp hurd was performed by reductive catalytic fractionation (RCF) in the presence of a metal catalyst. We found an unexpectedly high yield of monophenolic compounds (38.3 wt %) corresponding to above 95% of the theoretical maximum yield. The high yield is explained by both a thin cell wall and high S-lignin content. In addition, organosolv pulping was performed to generate a pulp that was bleached to produce dissolving-grade pulp suitable for textile fiber production (viscosity, 898 mL/g; ISO-brightness, 90.2%) and nanocellulose. Thus, we have demonstrated a novel value chain from a low-value side stream of hemp fiber manufacture that has the potential to increase textile fiber production with 100% yield and also give bio-oil for green chemicals.