## 4 Conclusions and Perspectives  
Due to its strong mechanical and structural functions, cellulose nanofiber has gained popularity for sustainable production in recent years [2]. The use of cellulose nanofiber from natural sources has grown significantly as the industry shifts away from unsustainable fossil fuel resources and looks toward a softer and more sustainable environmental approach. Figure 4: (**a**) Transmission electron micrographs (TEM) and (**b**) size distribution (mean diameter 18 \(\pm\) 7) of produced nanofibers (PL-HUS) from pineapple waste. Colombia currently produces more than one million tons of pineapple per year [20], which indicates that the country has a production potential of 800.000 tons of solid waste that is up to 80% cellulose [41], which gives this waste commercialization potential and the possibility of adding value to a Colombian pineapple waste. In Colombia, the use of petrochemical plastics has recently been regulated, which calls for the development of new biodegradable packaging materials. Such materials could be reinforced with nanocellulose fibers from pineapple leaves, which could mechanically reinforce thermosets and thermoplastics. Hydrophobic properties could also be enhanced by adding cellulose nanofibers as nanocomposites for adhesion in fiber-reinforced composites such as epoxies. Due to the morphology and characteristic physical properties of the obtained materials, cellulose nanofiber produced in this work could be a promising material for use in a wealth of fields and applications such as filter material, high gas barrier packaging material, electronic devices, foods, medicine, construction, cosmetics, pharmacy, and health care [2]: (i) due to their large specific surface area, cellulose nanofibers can accumulate small dust particles, which demonstrates their potential for air filtration (they could even support the development of nanofoams and aerogels to filter particles from the air); (ii) cellulose nanofibers are a great barrier against oxygen (due to their > 40% crystallinity) and have low thermal expansion, properties that give them potential for use in food production and preservation since cellulose nanofibers could act as gas barrier films to reduce air flow and to maintain food freshness, thus acting as biodegradable packaging; (iii) for construction, nanocellulose fiber coating materials could protect from ultraviolet rays and oxygen better than acrylic resin, so it has a higher potential to suppress the generation of radicals, such as discoloration and cracking; (iv) the thermal stability of cellulose nanofibers makes them excellent materials for use in electronic devices as they exhibit low porosity and roughness, increase print resolution, make electronic devices more conductive, and can prevent short circuits by distorting water permeation in electronic circuits; and finally, (v) these produced materials could be used as adsorbent, antimicrobial material and for controlled drug delivery. Conceptualization, M.A.G.-C., L.S.-C. and D.F.T. ; data curation, M.A.G.-C.; formal analysis, M.A.G.-C., L.S.-C. and D.F.T. ; funding acquisition, M.A.G.-C., L.S.-C. and D.F.T. ; investigation, M.A.G.-C.; methodology, M.A.G.-C., L.S.-C. and D.F.T. ; project administration, L.S.-C. and D.F.T. ; resources, M.A.G.-C., L.S.-C. and D.F.T. ; software, M.A.G.-C., L.S.-C. and D.F.T. ; supervision, L.S.-C. and D.F.T. ; validation, M.A.G.-C., L.S.-C. and D.F.T. ; visualization, M.A.G.-C., L.S.-C. and D.F.T. ; writing--original draft, M.A.G.-C., L.S.-C. and D.F.T. ; writing--review and editing, D.F.T. All authors have read and agreed to the published version of the manuscript. This research was funded by ASTIN-SENA (project reference 11796). Not applicable. The data that support the findings of this study are available from all authors upon request. The authors thank the Research Group on Development of Materials and Products (GIDEMP, ASTIN), students of the Technology in Chemistry Applied to Industry (SENA), and the biotechnology laboratories of Tecnoparque Nodo Cali.