Editor: Pertti Nousiainen, Professor Emeritus, Tampere University
Man-made bio-based fibre products
Everything you need to know about texile applications of wood — clothing, hygienic and medical applications.
The global textile fiber production has surpassed 116 million tonnes by 2022, driven by population growth and rising living standards. Over the past 125 years, fiber production has significantly evolved, with synthetic fibers such as polyester gaining dominance. Polyester was commercially established in 1941 and, following rapid economic expansion in the 1950s, synthetic fibers experienced exponential growth. In contrast, bio-based fibers, particularly cotton, could not keep pace with the annual demand increase of 1 million tonnes. As a result, the need for novel fiber sources that offer performance, easy-care properties, and cost-competitiveness has intensified.
Rise of Bio-Based Man-Made Fibers
To address the limitations of natural fibers, bio-based man-made fibers, primarily derived from dissolving cellulose, have gained prominence. Fibers such as viscose, cupro, and acetate have seen increased production due to their hydrophilic nature, which is essential for clothing, hygiene, and medical applications. The demand for viscose has grown to more than 6% of total fiber production, boosting the need for dissolving pulp, including sulphite and modified kraft pulp processes.
Environmental concerns regarding the sustainability of cotton, greenhouse gas emissions, chemical-intensive processes, and microplastic pollution in the textile industry have further favored the shift towards cellulose-based fibers. In response, advancements in viscose technology aim to develop low-sulfur and sulfur-free processes by recycling chemicals and using novel cellulose activation methods such as enzyme treatment to dissolve cellulose without derivatization.
Innovations in Cellulose-Based Fibers
Lyocell fibers, produced using NMMO (N-Methylmorpholine N-oxide) in a closed-loop process, now account for approximately 0.5% of total fiber production. In Finland, modifications to the air-gap spinning process of lyocell using ionic solvents are being explored. Additionally, a new process is under development that transforms bleached pulp directly into fibers using only water and a solvent, eliminating the need for additional chemicals.
Other advancements in cellulose fiber production include the application of cellulose carbamate technology since the 1980s. Although originally developed to mitigate the chemical risks of traditional viscose production, it has yet to become competitive enough to replace conventional viscose solely based on environmental benefits. Instead, carbamate technology has found applications in recycling cellulose fibers from mixed cotton textiles, denim, and even paper waste.
Process for Manufacturing Bio-Based Textile Fibers
The production of bio-based textile fibers primarily follows the dissolution-regeneration process, where cellulose from wood pulp is dissolved in a solvent and then regenerated into fibers. In this method, the cellulose structure is broken down to create a spinning solution, which varies depending on the fiber type. For instance, viscose is produced by treating cellulose with sodium hydroxide and carbon disulfide to form cellulose xanthate, which is then dissolved in an alkaline solution. Lyocell, a more environmentally friendly alternative, uses N-Methylmorpholine N-oxide (NMMO) as a direct solvent, avoiding chemical derivatization. Cupro fibers involve dissolving cellulose in a cuprammonium solution, while acetate fibers are produced through chemical modification with acetic acid, creating a thermoplastic spinning solution. Once dissolved, the spinning solution is extruded through spinnerets into a coagulation bath where the solvent is removed, and the fibers are regenerated. Viscose and cupro fibers are solidified in a sulfuric acid bath, while lyocell fibers are formed through solvent evaporation in a water-based system, allowing for high solvent recovery. Acetate fibers solidify upon cooling or solvent evaporation.
Beyond the conventional dissolution-regeneration process, alternative bio-based fiber production methods are being developed to enhance sustainability. One such method involves microfibrillated cellulose (MFC) into filaments, where cellulose is mechanically refined into nanoscale fibrils and aligned into continuous filaments without chemical dissolution. Another approach utilizes bio-based polymers for spinning, where natural monomers such as polylactic acid (PLA) from corn starch or furan-based polyesters are polymerized into fibers. Additionally, the Ioncell® process dissolves cellulose in ionic liquids without harmful chemicals, producing strong and biodegradable fibers. As the textile industry shifts towards eco-friendly solutions, these alternative methods offer promising advancements in reducing environmental impact while expanding the possibilities for bio-based fibers in various applications.
The Role of Synthetic Fibers and Bio-Based Alternatives
Despite the rise of bio-based fibers, polyester remains the dominant fossil-based fiber. Efforts to develop semi-bio-based polyester (PTT) have led to the production of trimethylene glycol from agricultural sources and, more recently, from wood residues. Research is also underway to replace oil-based terephthalic acid with bio-based furan dicarboxylic acid (FDCA), which could enable the production of fully bio-based polyester (PEF) with improved properties compared to conventional polyester (PET). However, biodegradable synthetic fibers are not yet competitive with aromatic polyesters in terms of cost, production volume, or performance.
Future Outlook for Cellulose Fibers
With limited availability of natural fibers, particularly cotton, regenerated cellulose fibers have strong growth potential. Global fiber production is expected to reach 150-200 million tonnes by 2050, with cellulose fibers needed in addition to cotton at an estimated volume of 15 million tonnes. Since 2010, several innovative cellulose-based concepts have emerged, including Spinnova’s fibril yarns, along with developments in alkaline and ioncel processes.
This growing demand for cellulose fibers will necessitate an increased supply of dissolving pulp and bleached pulp, creating opportunities for forest biorefining. Advancing pulping technologies and improving yield efficiency will be essential in making textile fiber production more carbon-neutral and sustainable. Proper forest management, including responsible harvesting and replanting (up to four trees planted for every tree cut), ensures long-term sustainability. Additionally, eucalyptus plantations are being used to prevent excessive deforestation of rainforests.
Sustainability and Environmental Impact
Lifecycle assessments of cellulose fibers, such as viscose and lyocell, indicate that their land use and emissions are lower than cotton, allowing more farmland to be allocated for food production. New process innovations are expected to further reduce emissions associated with cellulose fiber production. By extending the life cycle of wood-based fibers, the industry can move towards carbon-neutral textile products while minimizing waste.
In outlining this theme, a simple structure with five chapters was selected. The purpose of the first chapter Introduction to man-made bio-based fibre products highlights the growing demand for wood-based bio-fibers in the textile industry, focusing on production trends and future market projections. It provides a brief history of cellulose-based fibers, with an emphasis on wood-based MMCF, and discusses the key requirements of fibers for textile applications. The chapter also addresses the environmental benefits and challenges of wood-based fibers compared to other fiber types. Sustainability and environmental considerations are presented at the end of the Chapter with a specific focus on EU standardisation and legislation.
Second chapter on Man-Made Cellulosic Fibers (MMCF) and other wood-based fibers covers the essential building blocks of wood—cellulose, hemicellulose, and lignin—and their suitability for textile applications. It discusses the processing methods required for textile use, including dissolution, regeneration, and the production of bio-based polymers, with examples like Spinnova’s MFC. The chapter explores various cellulose dissolution processes (viscose, lyocell, NMMO, ILs) and innovations such as Ioncell, Kuura, and TreeToTextile. It also examines other wood-based fibers like cellulose acetate, Cupro, and bio-based synthetic fibers like UPM’s BioPura. Recycled textiles, fiber production machinery, and testing of MMCF and other fibers are also addressed, while the relevance of carbon fibers from wood is briefly considered.
In the following chapter Textile Products covers a wide range of textile applications, including clothing, technical textiles, nonwovens, and textile composites. It also addresses the testing of textiles, as well as legislation and standards governing textile production. The chapter explores the use and end-of-life aspects of textiles, focusing on the degradation mechanisms of fiber polymers and recycling processes, highlighting the sustainability of textile materials throughout their lifecycle.
Next chapter Transforming Fibres to Textiles outlines the key steps in textile production, starting with an introduction to the processing stages and terminology. It covers fiber and yarn spinning, including polymer behavior, the theory of fiber spinning, and the parameters in wet spinning. The chapter then delves into weaving and knitting, nonwoven technology, and textile composite processing. It also addresses the dyeing of textiles, highlighting different dyes and dyeing processes, as well as textile printing and finishing techniques, emphasizing the various methods used to enhance textile properties.
The final chapter “Other Regenerated Fibers” covers a range of innovative and bio-based fibers, including regenerated protein fibers, bio-based synthetic polyesters, and bio-based polyesters, with a focus on polyesters made from ethylene diol and biochemical recycling processes. It also explores biobased polyolefins, cellulose-silica hybrid fibers, and polyamides derived from ligno-cellulosics. The chapter discusses the industrial development of silkworm and spider silk, including their processing into protein fibers. Additionally, it highlights the development of multicomponent, micro-, and nanofibers, showcasing the diversity of regenerated fibers in textile applications.
