1902
Journal of Material Cycles and Waste Management (2025) 27:1901–1913
Materials and methods
recycling. The results showed that the length of the fibers in all of the materials remained nearly constant, whereas fines tended to decrease with each cycle, with the greatest loss occurring in the first cycle (up to 6 percent). With regard to the material's physical properties, there was no discernible shift in the zero-span strength, breaking length, or ring crush strength over multiple cycles. There has been much recent discussion about the sustain- ability of non-wood fibers relative to wood fibers for paper and board. The recyclability of these two types of fibers has not been reported but is critical in understanding the environmental life cycle of the fibers. Fibers that break eas- ily in recycling are at a sustainability disadvantage relative to fibers that can be recycled for more cycles. These more fragile fibers might be best directed to applications in which recycling is not performed (bath tissue) or for applications where the collection rate is low. This aspect of fiber recy- clability and its impact on holistic environmental life cycle analyses has been largely unreported. In the investigation herein, the behavior of wood and non- wood-based fibers through multiple recycling processes is explored with emphasis on the recycling fiber yield and the changes in paper and fiber physical properties. This study is unlike previous ones [3–7] in that a rigorous fiber yield is measured herein over multiple recycle loops. Mechani- cal refining of the fibers in the recycle loop was used to mimic the mechanical actions that occur during the paper recycling and papermaking process. The results indicate that fiber recycling yields for different fibers is a key parameter that needs to be addressed in determining how many times a fiber can be recycled before it is broken and lost from the paper recycling system.
Materials
Two types of wood fibers were used in this experiment which are southern United States unbleached softwood kraft pulp (UBKP) and southern United States semi-chemical hardwood pulp (SCHW). Unrefined and refined UBKP was obtained from Westrock Company, USA. The industrially unrefined and refined pulp freeness values were 740 and 670 mL Canadian Standard Freeness (CSF), respectively. The pulps were received as a 10% slurry then centrifuged and fluffed to about 27% consistency. Unrefined SCHW was received from Greif Industrial Company, USA as a 17% con- sistency pulp with a freeness at 707 mL CSF. Wheat straw pulp (WS) was procured from an industrial facility, utilizing chemical treatment with peroxide and a mechanical pulp- ing process. The freeness as received for the WS pulp was 437 mL CSF. A blend of 25% WS and 75% SCHW (WS25% + SCHW75%) was also prepared and evaluated.
Process of Multiple Recycling Loops Study
The experimental flowsheet for evaluating the yield and properties of the pulp over multiple recycle loops is illus- trated in Fig. 1 . There are six main steps: disintegration, thickening, Papirindustriens forskningsinstitut (PFI) refin- ing, hand sheet making, drying, and soaking/tearing. Details of each step can be found in the supplemental information section. An initial pulp was used in cycle 0, shown with orange arrows. The pulp was passed through six main pro- cess steps that are shown in the green arrows for multiple cycles. Where. m HS = Oven-dry mass of rectangular hand sheets, OD g
Fig. 1 Overall process of the study of multiple recycling loops
Made with FlippingBook flipbook maker