Mid Sweden University

Unlike fossil-based plastics, wood-based packaging materials can be produced in an eco-friendly manner using wood chip residuals from sawmills and pulpwood. To produce high-yield pulp like chemithermomechanical pulps (CTMPs) for paperboard and liquid packaging, it’s crucial to reduce the electric energy consumption during fiber separation. The ultimate objective is to revolutionize paperboard production by achieving a middle-layer CTMP process that consumes less than 200 kWh/t, significantly improving from the current 500-600 kWh/t energy demand.

Optimizing the CTMP impregnation process of sodium sulfite (Na2SO3) in wood chips is crucial for achieving uniform softening, ideally at the fiber level. The properties of the fibers are significantly affected by the content of lignin sulfonates within the walls of the fiber and the middle lamellae. In this study, we employed in-house developed X-ray fluorescence (XRF) techniques, validated by beamline measurements, to map the distribution of sulfonated lignin within fibers. It also seemed possible to enhance the surface area of lignin-rich pulp fibers while losing minimal bulk by refining them with well-optimized low consistency (LC) refining. We aim to achieve a highly efficient separation of coniferous wood fibers by co-optimizing the sulfonation and the temperature in the pre-heater and chip-refiner. Additionally, we explored how lignin's softening behavior and potential crosslinking influence subsequent unit operations, including pressing, peroxide bleaching, and drying, following the defibration process. In defibration during chip refining, the maximum softening of wood fibers is preferred to maximize fiber preservation and minimize energy consumption. However, optimizing the stiffness of finished pulp fibers is preferable to reduce bulk loss during paperboard production. It can strive to optimize processes to develop stronger, lighter, and more sustainable composite packaging materials. Reducing environmental impact and electric energy can help create a more sustainable future.

Lightweight materials with high strength are desirable for advanced applications in transportation, sports equipment, construction, automotive, and aerospace. Aspen is fast growing, has low flammability, and is renewable and readily available. In this study, we present a continuous, high-yielding, efficient, scalable, and sustainable approach for the fabrication of strong materials from aspen by synergistic selective chemical modification and continuous hot pressing. FTIR analysis revealed changes in the chemical composition of the wood polymers, including the introduction of anionic groups, while SEM images showed morphological and structural transformations such as smoother surfaces and a more compact wood structure. The proposed strategy achieved up to 258 MPa (530% increase) in tensile strength by combining enhanced ion-bonding and hydrogen-bonding with the alignment of cellulose nanofibrils and the solidification of softened, depolymerized lignin through cross-linking reactions. This work demonstrates the continuous large-scale production of lightweight, strong structural materials under energy-efficient and mild modification conditions, suitable for the green fabrication of next-generation advanced materials from wood. 

There is a growing need for increased knowledge regarding sustainable and health-conscious menstrual products, particularly as environmental concerns intersect with public health, equality, and education. Our recent research presents the development and assessment of an internal menstrual product made from wood-based, biodegradable, fossil and plastic-free materials. Designed for safe use for at least 12 hours, the product addresses the practical needs of modern users across diverse cultural and socioeconomic contexts. Laboratory testing, including toxicological assessments, absorption efficiency, and biodegradability analyses, confirms that the product meets high standards of safety and environmental performance. The design process emphasized comfort, hygiene, and suitability for extended daily use without increasing health risks, such as Toxic Shock Syndrome. Patents are pending both regarding the product design and regarding the production process conditions.

To complement and assist the product development, an interactive 3D educational tool was created to enhance menstrual and reproductive health literacy. This tool, tailored for young users and low-resource settings, has been evaluated in collaboration with schools, youth clinics, and international NGOs in high and low-income countries. The initiative responds to the persistent stigma surrounding menstruation and the limited access to accurate, inclusive, and culturally adapted educational resources.

A key research focus has been integrating sustainable material innovation with health education and exploring the potential for international standardization. The project also initiated steps toward the first global safety standard for menstrual products under ISO, promoting transparency, user safety, and global market readiness. Through stakeholder engagement, user studies, and pilot-scale manufacturing, this work demonstrates how eco-friendly menstrual products can support environmental goals while empowering users through education and accessibility.

By combining product innovation, education, and policy development, this research contributes to UN Sustainable Development Goals such as: Good Health and Well-being (SDG 3), Quality Education (SDG 4), Gender Equality (SDG 5), and Responsible Consumption and Production (SDG 12). It offers a scalable, evidence-based framework for improving menstrual health globally.

Improving the mechanical properties of wood and paper is crucial for enhancing their performance in structural and packaging applications. A particularly effective method for increasing strength is hot-pressing, where lignin softening has been proposed as a key mechanism underlying improved fiber bonding. In this study, we investigated the deformation behavior of Norway spruce lignin across temperatures of approximately 25-300 degrees C and moisture contents of 0-25 wt % using molecular dynamics simulations and paper hot-pressing experiments. We simulated key mechanical paper properties, including Young's modulus, glass transition temperature, and the diffusivity of water and lignin chains. Experimental results showed a pronounced increase in wet strength above 175 degrees C, which correlated with lignin softening and enhanced fiber-fiber bonding in the simulations. Our findings highlight the ability of molecular simulations to elucidate the mechanisms of lignin-driven bonding and provide a foundation for optimizing the use of lignin-rich materials in various applications.

Given the declining demand for newsprint and the rising demand for packaging materials, new applications for high-yield pulps (HYPs), such as sustainable packaging, are being developed. While the traditional use of HYPs as a major component in paperboard is growing alongside this demand, their use in other packaging types with different property demands requires quality modifications or improvements to enhance mechanical strength and/or barrier properties. The research presented here explores the role of lignin and lignin-rich fine content, combined with hot-press technology, in improving the paper produced with chemithermomechanical pulp (CTMP). Critical properties for some packaging materials, as tensile strength (dry and wet) and air permeability were evaluated. Results indicate that moderate delignification (15%) or increased fines content together with hot-pressing improves the evaluated properties. The highest dry tensile strength was achieved through soft delignification, tripling the resistance (from 27 to 83 kN m/kg). Maximum wet strength (28 kN m/kg) was obtained with 35% fines content and 260 °C hot-pressing, which also resulted in the densest sheets. Air permeability was significantly reduced, either through partial delignification or by increasing the fines content, resulting in values decreasing from approximately 2000–20 mL/min. This approach aims to develop more sustainable packaging materials without relying on wet strength additives typically derived from fossil raw materials. 

There is a growing demand for the utilization of sustainable materials, such as cellulose-based alternatives, over fossil-based materials. However, the inherent drawbacks of cellulosic materials, such as extremely low wet strength and resistance to moisture, need significant improvements. Moreover, several of the commercially available wet-strength chemicals and hydrophobic agents for cellulosic material treatment are toxic or fossil-based (e.g., epichlorohydrin and fluorocarbons). Herein, we present an eco-friendly, high-yield, industrially relevant, and scalable method inspired by birch bark for fabricating hydrophobic and strong cellulosic materials. This was accomplished by combining simple surface modification of cellulosic fibers in water using colloidal particles of betulin, an abundant triterpene extracted from birch bark, with sustainable chemical engineering (e.g., lignin modification and hot-pressing). This led to a transformative process that not only altered the morphology of the cellulosic materials into a more dense and compact structure but also made them hydrophobic (contact angles of up to >130°) with the betulin particles undergoing polymorphic transformations from prismatic crystals (betulin III) to orthorhombic whiskers (betulin I). Significant synergistic effects are observed, resulting in a remarkable increase in wet strength (>1400%) of the produced hydrophobic cellulosic materials.

The widespread use of synthetic plastics in packaging materials poses significant environmental challenges, prompting the search for biobased, biodegradable, and non-toxic alternatives. This study focuses on improving high-yield pulps (HYPs) as sustainable materials for packaging. Enhancing wet strength and barrier properties of papers from bleached chemi-thermomechanical pulps (BCTMPs) is crucial for their application in water- and air- resistant wrappers. Traditional wet strength agents raise environmental and health concerns; therefore, this research explores the use of lignin, in the form of microparticles (LMPs), as a natural biopolymer that offers a safer alternative. However, the low viscosity of LMPs hampers their dispersion as a coating, requiring thickening agents (such as cationic starch (CS), chitosan (CH) or sodium alginate) for an effective coating formulation. Results demonstrate a synergistic effect of LMP coatings with CH or CS, enhanced by hot-pressing at 260 °C for 30 s, which improves dry and wet mechanical properties and decreases air permeability. The use of LMPs as a water-resistant interlayer between BCTMP paper sheets further improves the wet tensile index to 40 kN·m/kg for CH + LMPs and 23 kN·m/kg for CS + LMPs interlayer, representing 55 and 38 % of their respective dry tensile indices. 

A strong and lightweight composite packaging structure can be produced in an environmentally friendly and energy-efficient manner. It is necessary to develop methods for producing lighter, higher-quality paperboard with better strength and stiffness while retaining the same brightness. Energy efficiency is important when producing chemthermomechanical pulps (CTMP). The CTMP for paperboard should be designed to retain maximum bulk, therefor it is imperative to avoid unnecessary reductions in softening temperature when improving fiber stiffness. Optimizing the impregnation methodology of sodium sulfite (Na2SO3) in wood chips requires equally distributing softening properties across fibers. Wood fiber softening determines the efficiency of fiber separation during chip refining. Sulfonated lignin in the fiber walls and mid-lamellae determines the softening properties of these structures, as well as promoting stronger joint connections between fibers. However, evenly distributed sulfonation is difficult to achieve due to wood chips' differences in size, density, and quality. To determine how sulfonated lignin is distributed within and between individual fibers, we have employed XRF (X-ray fluorescence) techniques developed in-house and validated by beamline. Using our synchrotron measurements at APS, USA, we can gain a better understanding of sulfur distribution within and between wood fibers. As shown in the CTMP samples on images, there is an uneven distribution of sulfur between fibers. Typically, CTMP sulfur homogeneity inspections require spatial resolutions of 10µm-15µm. The methodology is developed based on the resolution containing homogeneity information. We believe that even the sulfonation along the fiber shell is the most favorable process parameter to extract. Identifying where the sulfonate ions (-SO3-) end up in the lignin of the wood fiber structure may therefore be an important element of future process and product development. We can, however, learn more about the development of fiber-joint strength and strength uniformity in products by characterizing sulfur distribution at the sub fiber level.