Bio-based lms/nanopapers of banana tree pseudostem: From lignocellulosic wastes to added-value micro/nanomaterials

: The growing demand for products with lower environmental impact and the 25 extensive applicability of cellulose nanofibrils (CNFs) have received attention in several fields 26 of knowledge due to their attractive properties. In this study, bio-based films/nanopapers were 27 produced with CNFs from banana tree pseudostem (BTPT) wastes and Eucalyptus kraft 28 cellulose (EKC) and were evaluated by their properties, such as mechanical strength, biodegradability bio-based nanomaterials, with potential for being applied as emulsifying agents and special 40 membranes, enabling more efficient utilization of agricultural wastes.

of knowledge due to their attractive properties. In this study, bio-based films/nanopapers were 27 produced with CNFs from banana tree pseudostem (BTPT) wastes and Eucalyptus kraft 28 cellulose (EKC) and were evaluated by their properties, such as mechanical strength, 29 biodegradability and light transmittance. The CNFs were produced by mechanical fibrillation 30 (after 20 and 40 passages) from suspensions of BTPT (alkaline pre-treated) and EKC. 31 Films/nanopapers were produced by casting from both suspensions with concentrations of 2% 32 (based in dry mass of CNF). The BTPT films/nanopapers showed greater mechanical properties, 33 with Young's modulus and tensile strength around 2.42 GPa and 51 MPa (after 40 passages), 34 respectively. On the other hand, the EKC samples showed lower disintegration in water after 24 35 h and biodegradability. The increase in the number of fibrillation cycles produced more 36 transparent films/nanopapers and caused a significant reduction of water absorption for both raw 37 materials. The permeability was similar for the films/nanopapers from BTPT and EKC. This 38 study indicated that attractive mechanical properties and biodegradability could be achieved by 39 48 49 List of abbreviations 50 CNFs: Cellulose nanofibrils BTPT: Banana tree pseudostem EKC: Eucalyptus kraft pulp SEM: Scanning electron microscopy FEG: Field emission gun TS: Tensile strength DW: Disintegration in water WA: Water absorption FTIR: Fourier transform infrared spectroscopy The main reasons for the application of cellulose nanofibrils (CNFs) for the production 59 of bio-based materials are their high aspect ratio, crystallinity, high capacity in forming flexible 60 films/nanopapers, with low thermal expansion, high optical transparency, excellent mechanical 61 properties (tensile strength and Young's modulus), emulsifying potential in suspensions, and as 62 a barrier (to oil, oxygen and water vapor), in addition to being abundant and non-toxic. The 63 development of new bio-based devices using nanostructures from lignocellulosic materials is a 64 rather new but rapidly evolving research area (Siró and Plackett, 2010), as their application in 65 cementitious composites (Fonseca et al., 2016), coated papers (Mirmehdi et al., 2018a;2018b), 66 aerogels (Zhou et al., 2016), and nanostructured films (Lopes et al., 2018), among others. 67 The methods commonly used for CNFs production are mechanical, chemical, 68 physical and biological (Frone et al., 2011). Cellulose nanostructures are presented in the 69 literature with different denominations, such as nanocrystals, nanowhiskers, nanofibrils and 70 microfibrillated cellulose, depending on the structure of the cellulose (Nystrom et al., 2010). 71 The CNFs show diameters varying from 10 to 100 nm, being attained using a specialized 72 microfibrillator (grinder) with a mechanism consisting of forcing the cellulose fibers through an 73 opening between a rotating stone and a static one. The mechanism generates major shearing 74 forces that break down the hydrogen bonds from the multi-layered cell walls of the fibers to 75 individualized micro/nanofibril bundles (Siró and Plackett, 2010). In order to generate such 76 nanostructures, the raw fibers must pass through various physical and/or chemical pre-77 treatments. Chemical pre-treatments normally start with an alkaline treatment (Rosa et al., 2010) 78 consisting of fiber immersion in alkali solution, usually with strong basic compounds as NaOH, 79 under heating and vigorous mechanical stirring. Strong alkaline compounds can penetrate the 80 fiber structure and remove hemicelluloses and any other fiber components as the soluble 81 extractives (Vardhini et al., 2016). Another widely used pre-treatment is the bleaching, which 82 uses chlorinated compounds or hydrogen peroxide in intention to obtain pulp with greater 83 whiteness. This process reduces or removes lignin from the pulp, possibly causing an increase 84 in the cellulose content, chemical reactivity, dimensional stability, tensile properties, and 85 roughness (Zuber et al., 2012). Due to pollutant production issues, chlorinated compounds are 86 being avoided at this stage. The extent of these changes depends on the treatment time, 87 temperature, alkali concentration, degree of polymerization, and source of cellulose (Samei et 88 al., 2008). 89 Despite the enormous progress and great success in studies involving cellulose 90 nanofibrils in the most diverse areas of science, there are still several challenges regarding the 91 high costs and efficiency of the fibrillation on an industrial scale. Currently, the main source for 92 CNFs production has been commercial kraft pulp (Tonoli et al., 2016;do Prado et al., 2018).

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The kraft pulp, especially from Eucalyptus, is the main product of planted forests for the 94 purposes of cellulose production in Brazil. In the kraft pulping, wood in the form of chips is 95 treated under pressure, in tanks called digesters, with sodium hydroxide (NaOH) and sodium 96 sulfide (Na 2 S) in pH above 12. This chemical process aims to dissolve the lignin, preserving the 97 fiber resistance, thus obtaining a cellulosic pulp with yield between 50 -60% (Sixta, 2006). The 98 uses of kraft pulp range from paper for packaging products, tissue paper for personal care (toilet 99 paper, diaper, absorbents, paper towels and napkins) and environmental hygiene, to paper for 100 writing and printing. The pulp from Eucalyptus are known to present short fibers, with length 101 from 0.5 to 2.0 mm, and generally has less strength, with high softness compared to the long 102 fibers (Alves et al., 2011). The thickness of the fiber wall ranges, on average, from 2.5 to 6.0 103 μm (Trevisan et al., 2017 reduction of residues and on ensuring their application in other chains and products, looking for 117 reduction of the CO 2 footprint. 118 Since these wastes are considered lignocellulosic materials, the production of CNFs 119 from them aiming to develop added-value products could be a promising alternative. The 120 novelty here is the scientific data contribution regarding the production and properties of the 121 biodegradable films/nanopapers, mainly about their water vapor permeability, light 122 transmittance, contact angle with water and biodegradability of the films/nanopapers produced 123 with banana pseudosteam residues. These are important technical-scientific knowledge that are 124 scarse and insufficient in literature for up-scaling packaging applications for example. 125 Packaging industries are looking for those information and knowledge for advancement in the 126 pre-screening of renewable raw materials for micro/nanofibrils production and application in 127 substitution of petroleum-based polymers. of 24% (v/v) and NaOH in solution of 4% (w/v) for 2 h at 80°C (water bath) and with 161 mechanical stirring (1,500 rpm), for each 5 g of the previously alkaline-treated sawdust samples. 162 After the sequence of treatments, the samples were washed to remove residual reagents and 163 oven-dried at 50°C for 24 h. The yields were 59% after alkaline treatment (from the BTPT 164 natural sawdust to alkaline treated BTPT) and 60% after bleaching (from the alkaline treated 165 BTPT to the bleached BTPT), resulting in a total yield of 36% (from the BTPT sawdust to the 166 bleached BTPT). The main goals of the alkaline treatment and bleaching are to increase the 167 brightness of the pulp and promote the removal of components such as lignin and its 168 degradation products, extractives, metal ions, non-cellulosic carbohydrates and other impurities. 169 In this sense, and in accordance with the environment, it was proposed the use of peroxides, 170 instead of the chlorinated reagents (chlorine, hypochlorite and chlorine dioxide) widely used by 171 many pulp and paper industries, due to their lower cost and a higher yield of the final product. 172 In addition, the reagent concentrations used in the pre-treatments are low. 173 174

Chemical analysis of the raw materials 175
The wastes of BTPT (natural sawdust, alkaline treated and bleached) and the 176 commercial EKC were analyzed according to the amount of holocellulose (cellulose + 177 hemicelluloses; according to Browning, 1963), cellulose (Kennedy et al., 1987) The pre-treated sawdust of both the BTPT waste and the commercial EKC were 184 dispersed separately in 6 L of water, obtaining a suspension of 2% concentration (based in dry 185 mass of sawdust) and stirred for 10 min (200 rpm). It is important to point out that the EKC was 186 not subjected to any other pre-treatment after being obtained from the industry. The CNFs was 187 obtained from each raw material following the methods suggested by Guimarães Jr. et al. of the doubly diluted sample was dripped onto a silicon plate and dried at room temperature. 212 After this procedure, the samples were fixed to a sample holder using a conductive tape (carbon) 213 and kept for 24 h in a desiccator. A JEOL (JSM 6701) microscope equipped with a field 214 emission gun (FEG) was used with the following parameters: work distance 3 mm, acceleration 215 voltage 4 kV and current 10 μA without sample coating. The software ImageJ ® was used to 216 determine the diameters of the samples and CNFs in detail. The average diameter of the CNFs 217 was determined by the average of 100 measurements proceeded in the SEM-FEG micrographs. 218 The where TS is the tensile strength (MPa); M is the maximum load applied to the sample (N); A 0 is 234 the initial cross-section area of the sample (mm²). 235 where S is the stress value in the elastic region (GPa); and e is the specific elastic deformation 239 (mm/mm) corresponding to the applied stress. 240 241 2.6.2 Apparent density, grammage and thickness 242 The apparent density of the samples can be reported as the relation between the 243 film/nanopapers grammage and thickness, as mentioned in the TAPPI T220-om-01 (2004) 244 standard. The grammage corresponds to a specific mass of area (g m -2 ), obtained in accordance 245 with the TAPPI T410-om-02 (2004) standard. The thickness was directly determined by 246 averaging six random measurements on the samples using a digital micrometer (resolution of 1 247 µm). 248 249

Chemical and morphological properties 250
The chemical groups of the BTPT and EKC films/nanopapers samples were determined 251 by Fourier transform infrared spectroscopy, using a spectrophotometer Vertex 70 model 252 (Bruker, Germany), operating in attenuated total reflection (ATR) mode. Spectra were recorded 253 from 4,000 to 500 cm −1 spectral ranges, at a 32-scan rate, and a 4 cm −1 spectral resolution. The 254 effects of different passages (20 and 40x) on the surface and fracture of the samples and the 255 presence of pores in the films/nanopapers structure were observed using a JEOL ® JMS 6510 256 scanning electron microscope with a 10 kV voltage. The films/nanopapers were positioned on 257 aluminum stubs and covered with gold in order to obtain conductive samples. 258 259 2.6.4 Contact angle 260 The contact angle was evaluated by a Kruss Drop Shape Analyzer-DSA25 (Hamburg, 261 Germany). A water drop was deposited over the sample surface through a syringe. The drop 262 image was captured by a video camera and the contact angle between the water drop and the 263 sample surface was measured. The test was performed at room temperature (20°C). For each 264 CNFs film/nanopaper, three measurements were performed after the drop stabilization (2 s). 265 266

Moisture and water absorption after 2 h of immersion 267
The moisture was determined using the procedures described in the TAPPI T412-om-02 268 (2004) standard. Samples (diameter 30 mm) were immersed in water for 2 h for evaluation of 269 the water absorption (WA 2h) using Eq. (3). where Im is the initial mass of the acclimatized sample; Fm is the final mass of the sample after 274 2 h of water immersion. 275 276 2.6.6 Disintegration in water (DW) 277 Samples (diameter 30 mm) were kept at 65% RH and 20 ± 3°C, weighed and immersed 278 in 100 mL of distilled water for 24 h. The excess water was then removed, and the samples were 279 dried at 65% RH and 20 ± 3°C, as the initial condition, being weighed again. The disintegrated 280 portion of the samples after the immersion (DW) was calculated according to Eq. (4). The final 281 result was obtained from the average of three measurements for each film/nanopaper. The analysis of water vapor permeability of the films/nanopapers was carried out 290 following the permeability cell methodology described in Guimarães Jr et al. (2015b). This 291 method determines the amount of water vapor that passes through a known area of sample, 292 induced by the vapor pressure difference between two specific points on the exterior and interior 293 of the permeability cell. Samples with known thickness were sealed in a glass permeation cell 294 containing silica gel (relative humidity 0%; with no water vapor pressure), placed in a 295 desiccator and kept at 25°C and relative humidity 100%. The film/nanopaper was positioned in 296 the cap of the glass bottle, so that it formed a membrane between the exterior and interior of the 297 permeability cell (Figure 1). 298 299 #######Figure 1####### 300 The mass of the permeability cell was measured daily for 10 consecutive days. The biodegradability test was performed by measuring the mass loss of the 323 films/nanopapers when incubated in soil. It was evaluated according to the procedures described 324 by Bardi and Rosa (2007 The smaller diameters may explain the better performance of TS for the BTPT 362 films/nanopapers. BTPT presented longer starting fibers (~3.4 mm) (Figure 4) compared to 363 EKC pulp (~0.6 to 0.9 mm) ( Figure 5). According to Stelte and Sanadi (2009), fibrillation 364 occurs more rapidly for long fiber species and may be obtained with lower energy consumption. 365 The thickness of the cell wall can also result in easier fibrillation, the cell walls with lower 366 thickness being more favorable to mechanical treatment. Ogunsile   The significant reduction of film thickness that occurred with the increase of the number 387 of passages from 20 to 40 (Table 3)   The presence of fibers with ineffective deconstruction by the fibrillation process favors 401 failures and internal defects such as pores and microcracks, which act as stress concentration    The disintegration in water (DW 24h) for all the films ranged from 2.3 to 7.6% and 471 showed the same behavior of the water absorption after 2 h. The BTPT films/nanopapers 472 reduced by 5% the disintegration in water after 40 passages. For EKC, the reduction was 17%. 473 Regarding the type of raw material, the lower disintegration in water found for the EKC 474 films/nanopapers was probably because this raw material came from a commercial source, 475 where they are generally subjected to controlled processes and treatments in the industry, such 476 as reagents for hydrophobization, specific reagents for cellulose purification, and drying, among 477 others. In this sense, the performance of commercial pulps can generally have some advantages 478 when compared to those from agro-industrial wastes. Additionally, the BTPT presented higher 479 content of non-cellulosic chemical components as lignin and hemicelluloses (see Figure 2), 480 resulting in some difficulty of packing the micro/nanofibrils and lignin/hemicelluloses 481 fragments.

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The resistance of the films/nanopapers to disintegration in water may be an important 483 issue and CNFs of the surface, instead of the solubility of CNF components. 493 More cycles of fibrillation resulted in lower WVTR for the films/nanopapers produced 494 from EKC. This behavior was similar to that found for the parameters WA 2h, DW 24h and 495 moisture, which showed better performance after 40 passages. The films/nanopapers produced 496 from BTPT did not show significant differences between 20 and 40 cycles of fibrillation for 497 WVTR due to the overlapping standard deviations. The EKC films/nanopapers showed a reduction of about 8% in the WVTR. This was 505 assumed to be due to the increase of individualized CNF, after 40 passages, with a consequent 506 increase of the surface area. The compact and dense three-dimensional network formed by 507 hydrogen bonds did not allow the transport of water vapor through the film/nanopaper, since 508 there were no carbonyl and hydroxyl groups available to make bonds with the water molecules. 509 Therefore, the absence or low amount of empty spaces between the cellulose fibrils hinders the 510 diffusivity of water vapor. The improvement of barrier properties with the increase of the degree 511 of fibrillation is strongly associated with the decrease of the diffusion coefficient, caused by the 512 strong entanglements between the cellulose nanofibrils (Kaushik et al., 2010). Scatolino et al.

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(2017) found lower results for the properties of permeability and water disintegration when 514 evaluating nanocellulose films produced with Amazonian wood species, after more fibrillation 515 cycles. 516 The films/nanopapers produced from BTPT and EKC obtained lower values of WVTR 517 when compared to other nanostructured materials from vegetal sources reported in the literature, 518 in particular, almost the half of the WVTR values for films composed of potato starch. Films 519 produced with starch require improvements due to the hydrophilic structure resulting from the 520 presence of amylose and amylopectin in its composition (Romero-Bastida et al., 2015). 521 Excessively high values of WVTR can be explained by the existence of larger pores in the 522 microstructure of the films. The films/nanopapers from bleached wood as the raw material also 523 obtained higher values of WVTR compared to those produced in this study. The ideal structure 524 of CNFs networks is a compact complex form, presenting an obstacle to the water vapor 525 diffusion. These are potential results for packaging applications and advancement in the pre-526 screening of renewable raw materials for substitution of petroleum-based polymers applied in 527 multilayer packaging. Biodegradable and recyclable polymers with high barrier properties are 528 very important for application as novel layers or in composite mixtures in cardboards, card 529 papers, and industrial sacks for packaging. Films produced from biopolymer poly-lactic acid 530 (PLA) and the biodegradable poly-vinyl alcohol (PVA), still had WVTRs dramatically inferior 531 to those produced in this study, and their use in the formulation of composite mixtures are very 532 potential. Biodegradable polymers such as the above mentioned have several established 533 applications, ranging from plastic bags and cups, and small household items to materials for 534 electrical insulation. 535 536

Chemical structures of the films/nanopapers 537
The chemical structures (functional groups) of BTPT and EKC films/nanopapers were 538 compared by FTIR and the spectra indicated the expected similarities in chemical composition 539 for all samples. In general, the appearance or disappearance of peaks was not observed in the 540 spectrum analysis in the different raw materials used. An absorption band was observed at the 541 onset spectrum ( Figure 6) with a peak at 3,300 cm -1 , corresponding to the free OH groups 542 (Silverstein and Webster, 2000) and to the intermolecular hydrogen bonds. It was also observed 543 that the increase in the fibrillation passages through the grinder led to increased intensity of this 544 band for BTPT, especially for the films/nanopapers produced with CNFs with 40 passages, 545 suggesting more exposed hydroxyl groups in the cellulose structure in comparison to the EKC 546 films/nanopapers after 40 passages. A greater number of -OH bonds indicates a greater 547 interaction between fibers and consequently better mechanical performance for these samples, 548 as previously observed in  The vibrations around 2,900 cm -1 are attributed to the absorption of C-H symmetrical 559 and asymmetrical stretching originating from cellulose clustering, which is typical of organic 560 materials (Silverstein and Webster, 2000). A minimal change in this region, with the increase of 561 the number of passages, was observed for the different films/nanopapers obtained. 562 The peaks observed at 1,598 and 1,446 cm -1 are attributed to C=C axial deformations of 563 lignin aromatic rings (Alemdar and Sain, 2008; Thomas et al., 2015), demonstrating the 564 presence of lignin in the BTPT films/nanopapers (see Figure 2) and lower intensity for EKC. A 565 little content of 8% of lignin was found for the BTPT samples, while for EKC, no lignin content 566 was detected. 567 The band at 1,022 cm -1 was attributed to -C-O-C-pyranose ring vibration (Elanthikkal 568 et al., 2010). The crystalline regions existing in the CNF are directly related to the quality and/or 569 quantity of cellulose present in their bonds, and probably the greatest intensity of this band 570 occurred due to a greater reorganization after 40 passages, when followed by drying of the 571 fibrils that compose the BTPT films/nanopapers, as reported in the methodology section. This 572 may have occurred due to the characteristics reported in the previous sections related to the 573 production process, such as greater surface area, smaller diameter, greater aspect ratio and 574 greater homogeneity. This phenomenon was not observed for the EKC films/nanopapers, 575 however. Instead, a reduction of the intensity of these bands was observed, supposedly due to 576 some increase of the amorphous region with the increased fibrillation after 40 passages. 577 578

Light transmittance of the films/nanopapers 579
The fibrillation altered the average diameter of the CNFs, as well as the light 580 transmittance of the films/nanopapers (Figures 7 and 8). The higher the number of passages and 581 the degree of fibrillation, lower is the diameter of CNF, which varied from around 20 ± 5 to 15 582 ± 5 nm for BTPT and from 31 ± 23 to 21 ± 9 nm for EKC, demonstrating the effectiveness of 583 the mechanical fibrillation in the process to modify the raw materials from micro to nanoscale. 584 Smaller diameters were observed for the BTPT CNF. The results demonstrated that the increase of fibrillation decreased the optical barrier for 593 all the samples, allowing the passage of greater amount of light. The transmittance was 594 increased by around 5% for BTPT films/nanopapers (from 65 to 68%) and 12% for EKC the two raw materials evaluated in this study presented contents of non-cellulosic components in 607 their structures, the structure of the films from both raw materials enabled the passage of light, 608 besides to allow the visibility through its structure (Figures 7d and 8d), especially the 609 films/nanopapers produced with 40 passages. the films is the use of specific enzymes on the raw material (Long et al., 2017), which can result 628 in high quality of fibrillation, as well as chemical pre-treatments, besides the advantage of being 629 environmentally friendly. However, enzymatic treatment is limited due to its sensitivity to 630 different temperature ranges, pH and prolonged conditions. Additionally, parameters such as: drying could also be an interesting option for production of the films/nanopapers, however it 637 could make the process more expensive and request greater energy consumption. It is important 638 to highlight that depending on the application, transparent films are not required, since there are 639 several possibilities for using the product where there is no requirement for total transparency. 640 Transparency and diameter can be used to indirectly assess the degree of fibrillation of 641 the CNFs. The diameter measurements performed on the CNFs after 20 and 40 passages 642 indicate the efficiency of the fibrillation process, that is, their values were 20 ± 5 and 15 ± 5 nm, 643 for BTPT and 31 ± 23 and 21 ± 9 nm for the EKC samples, respectively. In addition to the 644 properties abovementioned, there was an improvement in the mechanical properties of tensile 645 strength, density, water absorption, contact angle, water vapor transmission rate; as well as the 646 large amount of hydroxyl groups on the CNFs surface (seen in the FTIR) and film compaction 647 (seen with SEM-FEG). All these factors enable to infer that there was an increase in the degree 648 of fibrillation of CNFs with more passages through the grinder. 649 The carboxyl content may have increased after alkaline treatment and after the passages 650 through the mechanical fibrillator. These initial processes have promoted an increase in the 651 amount of hydroxyl groups on the surface of the CNFs due to oxidation and the increase of the 652 surface area of the fibrillated material (deconstruction of the cell wall). Probably, the degree of 653 polymerization may have reduced after these steps, increasing the cationic demand of the 654 suspension. The literature shows a certain linear relation between the increase in the tensile 655 strength and rupture stress with the number of carboxylic groups on the fiber surface (Serra et 656 al., 2017), that is, the increase in the number of hydroxyls and carboxylate groups provides the 657 improvement in the tensile properties of CNFs films. In addition, the strength of plain paper 658 depends, among others, on the number of hydrogen bonds that form between cellulose fibers 659 when water is removed from the fibrous suspension. It is then expected that CNFs, with a larger 660 surface area and a greater number of carboxyl and hydroxyl groups (negative charges) on their 661 surface, will be able to form great contents of hydrogen bonds between them. 662 663

Biodegradability of the films/nanopapers 664
The mass loss after soil incubation is a commonly used parameter for measuring 665 changes caused by the microbial attack on polymers (Flemming et al., 1998). The mass loss 666 increased with the increase of incubation time, independent of the raw material ( Figure 9A). The 667 total mass losses after 18 weeks (126 days) for 20 and 40 passages were ~40% and ~46% for the 668 BTPT films/nanopapers and ~26% and ~24% for the EKC samples, respectively. Signs of 669 degradation such as cracks, color change, roughness, and the presence of stains on the surface of 670 the samples were observed ( Figure 9B) BTPT nanostructured films/nanopapers (20 and 40 passages) before and after biodegradation; 681 from (e) to (h) EKC nanostructured films/nanopapers (20 and 40 passages) before and after 682 biodegradation. 683 684 The first days of incubation correspond to the abiotic phase of biodegradation, in which 685 the macromolecules suffer hydrolysis. The mass reduction remained stable between the 5 th week 686 (35 days) and 10 th week (70 days), strongly decreasing again between the 11 th (77 days) and 16 th 687 (112 days) weeks. The decomposition was observed especially for BTPT films/nanopapers. In 688 part, this could be due to the pores observed in their cross-section (see Figure 3), which 689 facilitated the dispersion of degrading enzymes after the microorganism's attack. A consortium 690 of various aerobic bacteria and fungi working cooperatively degrades the cellulose to glucose 691 and cellodextrins (Chandra and Renu, 1998 Lignin is considered to provide a physical barrier that protects the cellulose and 703 hemicelluloses against decay enzymes (Higuchi, 1990). films/nanopapers produced with lignocellulosic biomasses. The incubation process in the 714 simulated soil creates a humid and dark environment, which favors the reduction of the 715 recalcitrance characteristics of the lignocellulosic biomass components. It can be said that BTPT 716 films/nanopapers presented higher biodegradation in comparison to EKC films/nanopapers, 717 which could in part be due to the reduced recalcitrance of the BTPT.

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The results obtained in this research provide insights about the management of the 719 lignocellulosic wastes obtained mainly from the processing of the banana cultivation. Thus, 720 further insights are required for improving the efficiency of the banana production chain, 721 reducing residual biomass wastes and CO 2 footprint with their possible application in other 722 chains and products. This research indicated the possibility of producing nanostructured 723 materials with high mechanical qualities using residual biomass, similar to films/nanopapers 724 produced with commercial wood pulps. Additionally, based on the attractive properties of 725 strength and biodegradability, it is suggested that the potential of cellulose nanofibrils combined 726 with polymers should be evaluated for purposes such as emulsifier agents, coating layers on 727 commercial papers and cardboards, or the production of functionalized CNFs with chelating 728 agents for the treatment of wastewater and absorption of heavy metals. The applications of these 729 biomass wastes for the production of biodegradable films and products contribute to reduce CO 2 730 footprint of banana production chain, reducing environmental problems and generating 731 economic benefits for agro-industry. 732 733

Conclusions and future prospects 734
The study demonstrated the potential of BTPT wastes for the production of 735 nanostructured films/nanopapers through the evaluation of their biodegradability, physical 736 (relations with water), barrier and mechanical properties. The increase in the number of 737 passages through the grinder fibrillator reduced the CNFs diameter. The higher 738 individualization of the raw material structures led to a greater specific area and greater bonding 739 between the CNFs after drying. Also, predominance of smaller empty spaces led to a greater 740 apparent density and greater film/nanopaper transparency. In general, the physical and 741 mechanical properties were improved with the increase of cycles of fibrillation due to the 742 formation of more compact and denser structures. The BTPT films/nanopapers showed also the 743 greatest mechanical properties after 40 passages, with a Young's modulus and tensile strength 744 of around 2.4 GPa and 51 MPa, respectively. Films/nanopapers produced after 40 fibrillation 745 cycles tended to show lower WVTR, especially those from the EKC. The total mass loss after 746 18 weeks of soil incubation for 20 and 40 passages were ~40% and ~46% for the BTPT 747 films/nanopapers, showing higher biodegradation in comparison to EKC. Further research is 748 required to look for alternative and eco-friendly pre-treatments or fibrillation methods that are 749 cost-effective for upscaling their application and efficient for complete fibrillation of the fiber 750 cell wall in nanoscale. Combined with other biodegradable polymers and chelating agents, the 751 CNFs could be used for promising purposes, such as coating layers on sack papers, cardboards, 752 card papers, and multilayered papers for packaging, as emulsifier agents, and the production of 753 special membranes for the absorption of heavy metals. Therefore, the production and 754 application of BTPT nanofibrils in other chains and products may reduce CO 2 footprint in the 755 banana production chain and may support environmentally conscious decision-making by 756 stakeholder companies, consumers, and professionals. 757 Declarations 758 759 Ethics approval and consent to participate 760 Not applicable.

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Consent for publication 763 Not applicable.

765
Availability of data and materials 766 The datasets supporting the conclusions of this article are included in the article. 767 Besides, the datasets used and/or analyzed during the current study are available from the 768 corresponding author on reasonable request.

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Competing interests 771 The authors declare that they have no conflict of interest.  BMRG contributed with the writing of the initial version, review, data collection, and 780 data analysis. MVS and MAM were major contributors in writing the manuscript, specifically 781 writing the initial version, review, and editing of the manuscript. SRF and LMM contributed to 782            A) Mass loss of the lms/nanopapers along the biodegradation and visual aspect of the samples before and after 18 weeks in simulated soil: from (a) to (d) BTPT lms/nanopapers (20 and 40 passages) before and after biodegradation; from (e) to (h) EKC lms/nanopapers (20 and 40 passages) before and after biodegradation; B) Typical optical microscopy images of the samples after 18 weeks after soil incubation. Red arrows show pores and stains. From (a) to (d) BTPT nanostructured lms/nanopapers (20 and 40 passages) before and after biodegradation; from (e) to (h) EKC nanostructured lms/nanopapers (20 and 40 passages) before and after biodegradation.

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