Cellulose is abundant in woody plants and trees and is a main component of cotton, a staple in the textile industry. However, cotton cultivation consumes lots of water and pesticides, and additional farmland for cultivation is scarce. ‘Regenerated’ cellulose fibres, produced by dissolving and spinning natural fibres into ‘new’ ones, are the second largest cellulosic fibre group after cotton. Commonly called man made cellulosic fibres (MMCFs, including viscose), they are produced from wood pulp cellulosic fibres or recycled textiles. Processing currently involves caustic alkalis and carbon disulphide (CS2), a serious health hazard. The NeoCel project, which received funding from the Bio-based Industries Joint Undertaking, a public-private partnership between the EU and industry, has delivered an environmentally friendly and sustainable solution.
Cellulose ‘digestion’ gets a helping hand
Project manager Mattias Wennerstål of RISE explains the NeoCel advances: “NeoCel is a new technology to produce MMCFs. Conventional cold alkali activation and dissolution face challenges; enhancing pulp reactivity is essential. We do this by shortening the cellulose chains and increasing the fibre porosity to increase solvent accessibility.” This facilitates dissolution at more moderate temperatures, thereby lowering energy consumption. Further, the NeoCel process liberates cellulose more gently and greenly without the use of CS2. Finally, it also reuses the key chemicals used for dissolution and fibre spinning, a breakthrough generating significant interest more generally for existing viscose plants and within the pulp industry. Sophisticated process modelling and an analytical toolkit enhanced the fundamental understanding of the cellulosic fibres on a molecular level to establish correlations between process parameters and fibre properties. Wennerstål elaborates: “The modelled process simulations are not only valuable for the NeoCel process, but are easily adaptable for other cellulose-processing applications and thus, relevant to a variety of stakeholders within the pulp, paper and textile fibre process industry.”
Greener methods with far reaching applicability
The NeoCel process supports a bio based economy, enables unprecedented process control and accommodates a variety of different pulp sources. Moreover, continuous (versus conventional batch) processing translates to high throughput for large scale production, a breakthrough in the field. Fibres produced in the lab were of comparable or higher quality relative to viscose. Pilot scale experiments and simulations showed that European production is economically viable if the process is integrated with an existing pulp mill. Finally, a life cycle analysis (LCA) showed that the NeoCel concept can achieve a 15-50 % lower environmental impact than commercial viscose production. Wennerstål states: “While it was no surprise to see that the environmental factors associated with the use of CS2 were improved, we did not expect to see so many other environmental markers improved to such a large extent, as shown by the LCA.” NeoCel successfully developed a scalable and continuous process for production of high quality MMCFs and demonstrated the techno economic benefits of investing in it. “Most importantly, NeoCel technology has significant environmental benefits,” concludes Wennerstål. Spin offs are now preparing to use the pulp to fibre methodology in hygiene and medical applications, such as production of compresses or bandages, and the pulp to dissolution process to form all cellulose composite materials. NeoCel should have broad sweeping impact on ‘greening’ products from T shirts and bandages to natural fibre reinforced composites for numerous fields.
NeoCel, fibre, pulp, cellulose, viscose, dissolution, CS2, MMCFs, pulp mill, man-made cellulosic fibres