Review Articles

Lignin, a prospective bioresource from plants, has been undervalued for several dozen years because of the unpredictable structures and their changeability during extraction. Recently, lignin has become a star for certain researchers who are aiming to develop sunscreen products offering production against UV radiation. The preparation of lignin into sunscreens as a natural alternative to chemical products may offer new perspectives. This review discusses how lignin isolation methods and the resulting structural characteristics affect UV absorption, thereby determining the potential of lignin as a UV-absorbing and blocking agent in sunscreen formulations. The application of lignin in cosmetics may present great benefit to humans and their skin care needs.

Lignocellulosic biomass is an abundant renewable energy resource whose total energy content far exceeds current global demand. Its polysaccharides, cellulose, and hemicelluloses are primary targets for valorization; however, the recalcitrant structure of plant cell walls necessitates effective pretreatment. Among physical, physicochemical, chemical, and biological methods, advanced oxidation processes (AOPs) have emerged as an efficient and environmentally compatible chemical strategy. This review systematically evaluates nine major AOPs for lignocellulosic biomass pretreatment: Fenton and Fenton-like processes, alkaline H₂O₂, peracetic acid, persulfate, ozone, photocatalysis, electrochemical oxidation, wet air oxidation, and cavitation-assisted methods. For each, reaction mechanisms, advantages and limitations, recent advances, economic considerations, and scale-up challenges are discussed. Persulfate-based systems, wet air oxidation, and hybrid strategies (e.g., photo-Fenton, alkaline H₂O₂–cavitation, electrochemical–ozone–H₂O₂) are identified as particularly promising. Future research should prioritize novel catalyst development, reactor optimization, multi-mechanism integration, and rigorous techno-economic and life-cycle assessments. Coupling AOPs with renewable energy sources will be critical to improving energy efficiency and enabling cost-effective large-scale application.

The paper industry has achieved relatively high levels of recovery and reuse of cellulosic fibers by the recycling of paper. The industry’s record of recovering material from used paper products far exceeds that of, for instance, the plastics industry. However, in the course of that success there are challenges. This paper provides a tutorial review of problems related to the stickies content of recovered used paper material. The review considers what stickies are composed of, how they can affect papermaking and its products, and how papermakers can minimize their adverse effects. Stickies tend to be problematic in mills without deinking systems. Though some stickies can be removed by screening, much of the material is expected to deform and thereby pass through industrial screens. Larger stickies (macrostickies) can be removed using hydrocyclones, whereas smaller ones (microstickies) are often removed using flotation. Other approaches to dealing with stickies include using detackifiers, which essentially means covering the stickies with a polymer or a mineral product. Production teams can optimize conditions to retain the stickies, ideally as small particles, onto cellulosic fibers. Because the processes are complex, and the composition of recovered stock tends to change over time, continuing efforts will be required. Effective control of stickies can be expected to require effective collaboration among people at the mill, chemical supplier companies, and machinery specialists.

This review examines the biomethane value chain from feedstock selection and feedstock-specific pretreatment to digester operation, gas upgrading, utilization pathways, and life-cycle constraints. Rather than evaluating biomethane by methane purity alone, it emphasizes the combined effects of feedstock quality, pretreatment intensity, process stability, upgrading energy demand, methane slip, digestate management, and end-use infrastructure. Key anaerobic digestion variables, including temperature, pH, volatile fatty acids, carbon-to-nitrogen ratio, organic loading rate, hydraulic retention time, and inhibitor control, are linked to process robustness. Major upgrading technologies, including water scrubbing, chemical absorption, pressure swing adsorption, membrane separation, and cryogenic separation, are compared in terms of methane purity, methane loss, energy demand, cost tendency and deployment fit. Biomethane shows the strongest mitigation potential when wastes are locally sourced, methane losses are controlled and digestate is safely recycled.

Corrugated board, traditionally used in packaging, is increasingly explored as a structural material for lightweight engineering applications, including furniture, panels, and temporary building components. This transition requires moving beyond empirical design rules toward performance-driven and optimization-based methodologies. This paper presents a critical review of optimization techniques applied to the structural design of corrugated board, with emphasis on the mechanical and numerical foundations required for physically reliable optimization. The reviewed studies were selected from major scientific databases using keywords related to corrugated board, structural optimization, finite element modeling, homogenization, surrogate modeling, machine learning, hygro-mechanical behavior, failure mechanisms, and experimental validation. Unlike earlier reviews focused mainly on industrial optimization practices and algorithms, this review highlights model fidelity, validation hierarchy, moisture sensitivity, local failure, interface damage, and the maturity of data-driven workflows. Analytical models, finite element approaches, homogenization frameworks, reduced-order models, and surrogate-assisted strategies are discussed in terms of their applicability to iterative optimization. Key design variables, including flute geometry, layer configuration, material anisotropy, and environmental conditions, are related to stiffness, strength, stability, ECT, BCT, and material efficiency. The main gaps include limited validation, simplified moisture-dependent and failure descriptions, weak interface-damage modeling, and the early development of digital-twin concepts for corrugated board design.

Machine Vision (MV) software has emerged as a powerful tool for timber species identification, offering significant advantages including species-level accuracy, cost-effectiveness, and the elimination of human errors. The development of MV software relies on three major supporting technologies: computer vision, machine learning (ML), and deep learning (DL). This paper provides an in-depth exploration of the role of DL, with a particular focus on convolutional neural networks (CNNs), in enhancing MV software for timber identification. The potential of CNN architectures is examined in detail, including a review of commonly used CNN models and their effectiveness in identifying different timber species. This paper also discusses current practices in developing CNN models for integration into MV software for timber identification tasks, highlighting the standards and procedures researchers should follow to ensure optimal performance and reliability. Additionally, the challenges associated with implementing CNN models for timber identification are addressed. They include limited model usability due to the diversity of timber species and geographical variation. Variability in methodologies, imaging devices, and data processing approaches across studies further complicates the comparison and integration of results. This paper emphasises the need for standardised practices and further empirical research to address these inconsistencies and improve CNN-based MV systems for timber identification.

The enzymatic breakdown of lignin generates a spectrum of aromatic monomers — including vanillin, guaiacol, syringaldehyde, vanillic acid, ferulic acid, and p-coumaric acid — that serve as platform chemicals for pharmaceuticals, fragrances, resins, and bio-based polymers. However, its complex and recalcitrant structure necessitates highly efficient enzymatic systems for depolymerization. This review systematically classifies ligninolytic enzymes into five functional categories: laccases, peroxidases (including manganese peroxidases, lignin peroxidases, and versatile peroxidases), cytochrome P450s, dye-decolorizing peroxidases (DyPs), and auxiliary enzymes, evaluating their distinct roles and synergies in lignin breakdown. Laccases emerge as particularly versatile biocatalysts due to their widespread occurrence, broad substrate specificity, and operational flexibility under diverse conditions. Peroxidases drive critical oxidative reactions, while DyPs represent a functionally robust peroxidase class with superior stability under extreme pH, temperature, and pressure. Complementary enzymes such as etherases and lignin-mimetic systems further expand the toolbox for lignin valorization. To overcome inherent limitations of native enzymes, protein engineering strategies were highlighted to enhance catalytic efficiency, stability, and substrate affinity. Additionally, enzyme immobilization on advanced matrices (e.g., metal-organic frameworks) is discussed as a breakthrough approach to improve reusability and reaction scalability. These integrated advancements pave the way for sustainable lignin valorization.

Biogas produced through the anaerobic digestion of organic biomass is a renewable energy source with significant potential to replace fossil fuels. However, impurities such as carbon dioxide, hydrogen sulfide, and water vapor reduce its calorific value and cause operational challenges. Upgrading is therefore essential to increase methane concentration and biogas quality. Among various upgrading technologies, adsorption using activated carbon offers a practical, low cost, and energy efficient alternative. Activated carbon derived from lignocellulosic biomass exhibits high surface area (up to 3000 m²/g), tunable pore structure, and resistance to moisture saturation, making it suitable for carbon dioxide and methane separation. Activation techniques, both physical (using carbon dioxide or steam) and chemical (using potassium hydroxide or phosphoric acid), significantly influence surface functional groups and pore distribution. Natural and synthetic binders such as bentonite clay, methyl cellulose, and polyvinyl alcohol can enhance mechanical strength and adsorption stability in humid conditions. This review considers the structure, activation, and adsorption mechanisms of biomass derived activated carbon for biogas purification. Future research directions include hybrid composite development, functional surface modification, and performance evaluation under industrial biogas conditions. Overall, activated carbon represents a sustainable and efficient adsorbent supporting the transition toward cleaner and low carbon energy systems.

The transition toward a circular economy has established biodegradable polymer composites as a critical platform for active food packaging. This review systematically examines the structural design, functional mechanisms, and application performance of natural biopolymer matrices, including polysaccharides and proteins. Physicochemical coupling among polymer-network architecture, interfacial interactions, and active-agent dispersion governs the integration of antimicrobial, antioxidant, gas-barrier, UV-shielding, moisture-regulating, and stimuli-responsive functions. Particular emphasis is placed on controlled mass transfer and release kinetics at active packaging interfaces. Active-agent delivery is governed by molecular diffusion, polymer-network relaxation, carrier structure, and microenvironmental triggers such as pH, humidity, and temperature, which collectively determine the effective concentration and duration of antimicrobial and antioxidant activity. These structure–release–function relationships are further evaluated in high-moisture foods, respiring fruits and vegetables, and low-moisture or lipid-rich products. In addition, this review discusses the major constraints on industrial translation, including the migration and regulatory compliance of intentionally and non-intentionally added substances, nanoparticle safety, environment-dependent biodegradation, life cycle impacts, and thermomechanical challenges associated with continuous processing. Future development should move beyond passive material substitution toward the integrated design of active and intelligent packaging, scalable manufacturing, food-specific performance validation, and multi-objective optimization of functionality, safety, cost, and end-of-life behavior.

The utilization of starch-based bioplastics as renewable and environmentally friendly alternatives to replace traditional petroleum plastics has gained significant traction in recent years due to their biodegradability, renewability, and cost-effectiveness. However, their widespread industrial applications are hindered by shelf-life constraints, high moisture sensitivity, and poor performance when subjected to variations in microbial and temperature changes. In addition, starch-based bioplastics are formulated in complex mixtures, which may result in process-related toxicity. This review critically investigates these performance issues in depth, including toxicity potential, shelf-life, microbial resistance development, thermal stability, and physical appearance. Particular emphasis is placed on the safety of natural starch sources, the influences of environmental conditions on degradation behavior, and the incorporation of natural additives to enhance material properties. By considering these factors, this review aims to facilitate the development and selection of sustainable, safer, and environmentally friendly starch-based bioplastics for diverse future applications.