Degradation of Cellulose Derivatives in Laboratory, Man-Made, and Natural Environments

Abstract

Biodegradable polymers complement recyclable materials in battling plastic waste because some products are difficult to recycle and some will end up in the environment either because of their application or due to wear of the products. Natural biopolymers, such as cellulose, are inherently biodegradable, but chemical modification typically required for the obtainment of thermoplastic properties, solubility, or other desired material properties can hinder or even prevent the biodegradation process. This Review summarizes current knowledge on the degradation of common cellulose derivatives in different laboratory, natural, and man-made environments. Depending on the environment, the degradation can be solely biodegradation or a combination of several processes, such as chemical and enzymatic hydrolysis, photodegradation, and oxidation. It is clear that the type of modification and especially the degree of substitution are important factors controlling the degradation process of cellulose derivatives in combination with the degradation environment. The big variation of conditions in different environments is also briefly considered as well as the importance of the proper testing environment, characterization of the degradation process, and confirmation of biodegradability. To ensure full sustainability of the new cellulose derivatives under development, the expected end-of-life scenario, whether material recycling or "biological" recycling, should be included as an important design parameter.

Figure 1

Chemical structure of cellulose and some of its common derivatives where the R can be a hydrogen (H) atom or one of the groups presented in the figure.

Figure 2

Enzymatic hydrolysis of common cellulose derivatives where the degree of hydrolysis (%) is shown as the function of the degree of substitution (DS) after a 2 day incubation. Reprinted by permission from ref (51). Springer Nature, Journal of Polymers and the Environment, Enzymatic Degradation and Pilot-Scale Composting of Cellulose-Based Films with Different Chemical Structures, Leppänen, I.; Vikman, M.; Harlin, A.; Orelma, H. Copyright 2020 http://creativecommons.org/licenses/by/4.0/ (No changes were made to the copyrighted material).

Figure 3

Extent and rate of biodegradation of different lignocellulose materials. Reprinted by permission from ref (57). Springer Nature, Cellulose, Effect of lignocellulosic fiber composition on the aquatic biodegradation of wood pulps and the isolated cellulose, hemicellulose and lignin components: kinetic modeling of the biodegradation process, Kwon, S.; Zambrano, M.C.; Pawlak, J. J.; Venditti, R.A. Copyright 2021.

Figure 4

Influence of the DS on the ability of B. subtilis to adhere on the surface of the CA films. Reprinted from ref (58). Copyright 2022 American Chemical Society.

Figure 5

Biodegradation of (a) cellulose acetate with a DS of 1.85, 2.07, and 2.57 during 14 days and (b) cellulose propionate with a DS of 1.77 and 1.84 during 30 days. The degree of biodegradation was calculated from the release of ¹⁴CO₂. Reprinted with permission from ref (59). Copyright 1993, John Wiley and Sons.

Figure 6

Normalized biogas production during anaerobic degradation of unmodified and modified CNF. Reprinted from ref (64). Copyright 2021 American Chemical Society.

Figure 7

Aerobic biodegradability of hemicellulose and PCL-grafted hemicellulose using the standard ISO 14851 method. Reprinted from ref (65). Materials & Design, 153, Farhat, W.; Venditti, R.; Ayoub, A.; Prochazka, F.; Fernández-de-Alba, C.; Mignard, N.; Taha, M.; Becquart, F. Toward thermoplastic hemicellulose: Chemistry and characteristics of poly(ε-caprolactone) grafting onto hemicellulose backbones, 298–307. Copyright 2018, with permission from Elsevier.

Figure 8

Weight loss of (a) CA and CD modified CA+CD films with and without UVA irradiation in air or in simulated seawater during 30 days. For the sample marked *, the real weight loss was likely even larger due to some salt deposition on the samples. (b) Images of the aged samples showing basically unaffected films with the exception of CD modified and UVA irradiated samples that had totally fragmented in agreement with the large weight loss. Reprinted from ref (71). Copyright 2021 American Chemical Society https://creativecommons.org/licenses/by/4.0/ (No changes were made to the copyrighted material).

Figure 9

Images of (A) CA films, (B) plasticized CA films, (C) CA foams, (D) CA fabric, (E) kraft paper, (F) cotton fabric, (G) LDPE film and (H) PET fabrics after 0–13 weeks of incubation in a continuous flow seawater mesocosm. Reprinted from ref (74). Copyright 2022 American Chemical Society https://creativecommons.org/licenses/by-nc-nd/4.0/ (No changes were made to the copyrighted material).

Figure 10

Biodegradation rate of cotton, polyester, rayon, 50/50 polyester/cotton, and MCC as measured by the oxygen uptake. The inoculums originated from lake water, seawater, and activated sludge. Reprinted from ref (79). Marine Pollution Bulletin, 151, Zambrano, M. C.; Pawlak, J. J.; Daystar, J.; Ankeny, M.; Goller, C. C.; Venditti, R. A. Aerobic biodegradation in freshwater and marine environments of textile microfibers generated in clothes laundering: Effects of cellulose and polyester-based microfibers on the microbiome, 110826. Copyright 2020, with permission from Elsevier.

Figure 11

Effect of the DS on compostability of CA as measured by weight loss and molecular weight changes. Reprinted with permission from ref (94). Copyright 1994, John Wiley and Sons.

Figure 12

Weight loss (%) of compostable foodware and packaging products after (a) 65 days in turned window; (b) 45–49 days of anaerobic digestion; (c) 50 days in static pile; (d) 82 days of in-vessel composting. Reprinted from ref (96). International Biodeterioration & Biodegradation, 125, Zhang, H.; McGill, E.; Ohep Gomez, C.; Carson, S.; Neufeld, K.; Hawthorne, I. Disintegration of compostable foodware and packaging and its effect on microbial activity and community composition in municipal composting, 157–165. Copyright 2017, with permission from Elsevier.

Figure 13

Degradation of CA with different DSs after deacetylation pretreatment. (a) Enzymatic degradation rate by cellulase and a mixture of lipase and cellulase; (b) the appearance of the films after composting up to 42 days; (c) corresponding weight loss; (d) appearance of pretreated cigarette filters after composting up to 30 days. Reprinted from ref (58). Copyright 2022 American Chemical Society.