Citation: da Silveira, P.H.P.M.; Cardoso, B.F.d.A.F.; Marchi, B.Z.; Monteiro, S.N. Amazon Natural Fibers for Application in Engineering Composites and Sustainable Actions: A Review. Eng 2024, 5, 133–179. https://doi.org/10.3390/eng5010009 Academic Editor: Antonio Gil Bravo Received: 24 November 2023 Revised: 29 December 2023 Accepted: 2 January 2024 Published: 12 January 2024 Copyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Review Amazon Natural Fibers for Application in Engineering Composites and Sustainable Actions: A Review Pedro Henrique Poubel Mendonça da Silveira 1,2, * , Bruno Figueira de Abreu Ferreira Cardoso 2 , Belayne Zanini Marchi 2 and Sergio Neves Monteiro 2 1 West Zone Campus, Rio de Janeiro State University—UERJ, Avenida Manuel Caldeira de Alvarenga, 1203, Campo Grande, Rio de Janeiro 23070-200, RJ, Brazil 2 Department of Materials Science, Military Institute of Engineering—IME, Praça General Tibúrcio 80, Urca, Rio de Janeiro 22290-270, RJ, Brazil; brunofigueira1991@gmail.com (B.F.d.A.F.C.); belayne@ime.eb.br (B.Z.M.); snevesmonteiro@gmail.com (S.N.M.) * Correspondence: pedroo.poubel@gmail.com Abstract: The Amazon rainforest, spanning multiple countries in South America, is the world’s largest equatorial expanse, housing a vast array of relatively unknown plant and animal species. Encompassing the planet’s greatest flora, the Amazon offers a tremendous variety of plants from which natural lignocellulosic fibers (NLFs) can be extracted. In this century, NLFs, which have long been utilized by indigenous populations of the Amazon, have garnered interest as potential reinforcements for composites, whether polymer- or cement-based, in various technical applications such as packaging, construction, automotive products, and ballistic armor. A comparison with synthetic materials like glass, carbon, and aramid fibers, as well as other established NLFs, highlights the cost and specific property advantages of Amazon natural fibers (ANFs). Notably, the sustainable cultivation and extraction of ANFs, as alternatives to deforestation and livestock pasture, contribute to the preservation of the Amazon rainforest. This review article provides a comprehensive examina- tion of recent studies directly related to ANF-reinforced polymer matrix composites. The specific advantages, proposed applications, and reported challenges are highlighted, shedding light on the potential of these unique natural fibers. Keywords: natural lignocellulosic fibers; NLFs; Amazon rainforest; composite materials; engineering applications; sustainability; properties 1. Introduction Nature has provided a comprehensive diversity of natural fibers throughout the ages. With a remarkably extensive history, these fibers have roots that date back to prehistoric times, unquestionably meeting human needs throughout history [1–3]. Vegetable fibers have been used for various purposes in different eras and regions of the world. Primitive humans used them to keep warm, protect themselves, and as materials for household utensils such as ropes and fishing nets [1,4–6]. The use of vegetable fibers for textiles dates back to the end of the Paleolithic period (12,000–8000 BC). Discoveries, like palm leaf fragments in a 10,000 BC Mexican cave and net bags in a Utah cave, reveal Native Americans’ skills in processing vegetable fibers [1]. Table 1 outlines the history of natural fiber use in prehistoric eras. Vegetable fibers played a crucial role in human history, influencing agricultural, fish- ing, artisanal, and commercial activities [7,8]. Civilizations aimed to enhance their quality of life, driving improvements in living standards, technology, economics, and societal strength [6,8]. Technological progress in vegetable fiber production surged after the 18th- century Industrial Revolution, fostering economic growth. However, it brought challenges like increased resource consumption and pollution, impacting global sustainability ef- forts [9,10]. Eng 2024, 5, 133–179. https://doi.org/10.3390/eng5010009 https://www.mdpi.com/journal/eng