1 The emerging role of bio-based nanocomposites in sustainable engineering applications: Current progress and future directions 1 The growing demand for sustainable materials has advanced bio-based nanocomposites that merge renewable polymers like poly (lactic acid) (PLA) and nanocellulose with nanotechnology to achieve superior mechanical and eco-friendly performance. This paper shows recent advances and the emerging role of novel nanomaterials such as graphene, silica, and nanocellulose, while addressing challenges of compatibility, biodegradation control, and scalable green synthesis. Overcoming these issues through integrated sustainable approaches is vital for expanding their industrial and biomedical applications within a circular and eco-friendly materials framework. 1 2 Zahra Moazzami Goudarzi Laboratory of Polymers and Biomaterials, Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawinskiego 5B, 02-106 Warsaw Poland zmoazami@ippt.pan.pl Sohrab Asgaran Helmaco Sp. Z o.o. Company, Ostrobramska 101 / 335K, 04-041 Warszawa Poland S.a@helmaco.com Bio-based nanocomposites Sustainable engineering Environmental compatibility [1] M.S. Saharudin, R. Ilyas, N. Awang, S. Hasbi, I. Shyha, F. Inam, Advances in sustainable nanocomposites, MDPI, 2023, p. 5125.##[2] A.K. Mohanty, S. Vivekanandhan, J.-M. Pin, M. Misra, Composites from renewable and sustainable resources: Challenges and innovations, Science 362(6414) (2018) 536-542.##[3] C. Montanari, P. Olsén, L.A. Berglund, Sustainable wood nanotechnologies for wood composites processed by in-situ polymerization, Frontiers in Chemistry 9 (2021) 682883.##[4] O. Okolie, A. Kumar, C. Edwards, L.A. Lawton, A. Oke, S. McDonald, V.K. Thakur, J. Njuguna, Bio-based sustainable polymers and materials: From processing to biodegradation, Journal of Composites Science 7(6) (2023) 213.##[5] T. Wei, L. Lei, H. Kang, B. Qiao, Z. Wang, L. Zhang, P. Coates, K.C. Hua, J. Kulig, Tough bio‐based elastomer nanocomposites with high performance for engineering applications, Advanced Engineering Materials 14(1‐2) (2012) 112-118.##[6] N. Tripathi, M. Misra, A.K. Mohanty, Durable polylactic acid (PLA)-based sustainable engineered blends and biocomposites: Recent developments, challenges, and opportunities, ACS Engineering Au 1(1) (2021) 7-38.##[7] S. Sayyar, E. Murray, B.C. Thompson, S. Gambhir, D.L. Officer, G.G. Wallace, Covalently linked biocompatible graphene/polycaprolactone composites for tissue engineering, Carbon 52 (2013) 296-304.##[8] M.N. Norizan, S.S. Shazleen, A.H. Alias, F.A. Sabaruddin, M.R.M. Asyraf, E.S. Zainudin, N. Abdullah, M.S. Samsudin, S.H. Kamarudin, M.N.F. Norrrahim, Nanocellulose-based nanocomposites for sustainable applications: a review, Nanomaterials 12(19) (2022) 3483.##[9] M. Stepanova, E. Korzhikova-Vlakh, Modification of cellulose micro-and nanomaterials to improve properties of aliphatic polyesters/cellulose composites: a review, Polymers 14(7) (2022) 1477.##[10] F.V. Ferreira, C.G. Otoni, J. Kevin, H.S. Barud, L.M. Lona, E.D. Cranston, O.J. Rojas, Porous nanocellulose gels and foams: Breakthrough status in the development of scaffolds for tissue engineering, Materials Today 37 (2020) 126-141.##[11] A. Ebrahimzadeh, N. Sedaghat, A Review of Biodegradable Plastics Based on Polysaccharide: Starch, Cellulose and its Derivatives, Packaging science and art 13(51) (2023) 57-72.