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Green chemicals and technologies for the wood-to-textile value chain

Periodic Reporting for period 2 - GRETE (Green chemicals and technologies for the wood-to-textile value chain)

Reporting period: 2020-11-01 to 2022-04-30

The GRETE project tackles the increased global demand for sustainable textile fibres by offering new technological breakthroughs for the wood-to-textile value chain. Increased use of man-made cellulose fibres is targeted because of the sustainability issues related to cotton. Although cotton is a renewable resource, its cultivation requires irrigation water, arable land, fertilizers and pesticides that increase its negative environmental impact.

Currently the raw material base for the production of man-made cellulose fibres from wood is limited. GRETE will introduce technologies that enable the use of paper grade pulps from softwood and hardwood as raw materials for man-made textile fibres. GRETE will also offer safe and sustainable solvent systems for the production of regenerated cellulose fibres, instead of the present ones which are based on toxic or explosive chemicals. The novel solvents developed in GRETE are ionic liquids (IL’s), which will be non-toxic, recyclable and synthesized from low-cost industrially available chemicals. GRETE will also develop innovative technologies for chemical modification and enzymatic pre-treatment of pulps prior to cellulose dissolution. Chemical modification carried out either before or after dissolution and regeneration of pulps will bring chemical functionalities to fibres. The modifications either directly improve fibre properties (e.g. decreased fibrillation, improved fire resistance) or offer an easy route to further fibre processing. Improved dye adsorption and chemical reactivity will offer new options for dyeing and finishing treatments of the fibres, enabling e.g. the creation of a water-scarce end to the textile manufacturing value chain as well as open up the possibility for novel targeted and water-scarce finishing treatments.
During the first three years, work in the GRETE project has focused on the development of novel superbase ionic liquids, enzymatic modifications of paper grade pulps, spinning of man-made fibres from the novel ionic liquids, chemical modification of paper grade pulps and spun fibres, recycling of the superbase ionic liquids and models to assess technical, economic and environmental aspects of the GRETE concept.

The development of novel superbase ionic liquids has proceeded well. Roughly 20 new superbase structures have been synthesized and the cellulose dissolution capability of their corresponding acetate salts (superbase ionic liquids, SB-ILs) have been tested, as well as their hydrolytic and thermal stabilities. From these candidate structures, two new SB-ILs with low melting points, high thermal and hydrolytic stability and high capability to dissolve cellulose have been selected for further assessment. Toxicity of these novel SB-ILs has been studied using the marine bacterium Vibrio fischeri model and found to be harmless. Both of the selected novel superbase ILs have been produced on kg scale. Additionally, the work on the continuous production of 1st key novel superbase has been almost completed.

The mechano-enzymatic modification of kraft pulps has enabled good control over cellulose molar mass prior to dissolution which is a prerequisite for high quality dopes for fibre spinning. Chemical modifications targeting improved technical properties of regenerated fibres have been performed for the paper grade pulps. Novel hydrolytic and oxidative enzymes for targeted studies on pulp modification have been developed and used to prepare samples for dissolution studies. Dissolution and regeneration of proteins have been studied to examine their potential use in cellulosic fibres.

Regenerated cellulose fibres have been spun from the enzymatically and chemically modified pulps using the novel superbase ILs. The chemical modifications have been stable during dissolution and regeneration. An analysis method to determine the amount of residual IL in the regenerated fibres has been developed. Post-modifications of regenerated fibres have been successful to introduce improved dyeing and fire retardant properties to the fibres. Strategies for recycling the superbase ILs have been evaluated using computational and laboratory experiments including the use of membranes and two-phase aqueous extraction. Characterization of impurities from the dissolution and regeneration process and degradation products of superbase ILs have been analysed using sophisticated analytical tools.

The mass and energy balances have been calculated for four GRETE concepts and detailed description how the different process areas (pre-treatment, dissolution, regeneration, spinning, fiber washing, fiber drying, solvent recovery) have been modelled. The GRETE concepts have been compared with the reference concept (Lyocell process). The resulting mass and energy balances are used as inputs for technical, economic and environmental assessments. An excel model for calculating the economic profitability of the different production concepts has been generated. Preliminary, partial LCA calculation of the system in scope has also been also conducted. Joint efforts on obtaining coherent environmental LCA and the socio-economic feasibility analysis results with the financial evaluation results have been organised.

Attention has been paid to the effective exploitation and dissemination of the project results. The exploitation has taken place via GRETE website, newsletters, printed materials (i.e. GRETE roll-up banner, postcard and business card) and several audio-visual materials. Project partners have also been active in the dissemination activities including scientific publications and taking part in events and conferences. Also, events targeted for the Stakeholder Group (SHG) have been organized. To ensure smooth flow of the project, consortium meetings (organized every ~6 month) as well as Management Committee (MC) meetings have been organized.
The scientific work carried out in GRETE shows novelty and scientific progress. Several topics hold potential for manuscript preparation. For instance, the developed superbase structures are not commercially available nor known in the literature. It is expected that by the end of the project a family of novel solvents for cellulose dissolution will be available for industrial scale-up. These novel solvents are chemically stable, recyclable and non-toxic allowing environmentally benign and economically viable pathway for cellulose processing to textile fibers. New information concerning the enzymatic modification of kraft pulps, recycling of the superbase ILs have been obtained that pave the way for industrial exploitation of the technologies.

Research in the project is continued and expected to demonstrate new sustainable technologies that enable manufacturing materials and new consumer products with decreased chemical load and water consumption from European biomass to replace the need of fossil-based feedstock or cotton. The impact of the project is expected to be seen on industrial level and consumer markets between 5-10 years from the end of the project.